Online Program Schedule

The program schedule is subject to change. Check this site for updates. When you arrive at the meeting site, check the final schedule for any last-minute changes.

Session Schedule & Abstracts

Please note that we’re in the process of correcting typographical errors. If you see such errors, please report them to Larry Witmer (, but changes to content will not be made.

Thursday 30th June, 2016

Poster session & reception 1

Room: Grand Foyer   7:30 pm–9:30 pm

Sensory Biology and Neuroscience (SBN)
POS1-1  7:30 pm  Structural changes in the olfactory organs of Taricha granulosa, the rough-skinned newt, between aquatic and terrestrial phases. Bronson A, Humboldt State University; Snee E*, Humboldt State University; Cummings A, Humboldt State University; Reiss J, Humboldt State University
Abstract: The olfactory organs and associated tissues in larval, aquatic adult phase, and terrestrial adult phase rough-skinned newts (Taricha granulosa) were examined by scanning electron microscopy and traditional histology. In adults of both aquatic and terrestrial phase newts the olfactory organs are paired, flattened sacs, extending from the external nares anteriorly to the internal nares posteriorly. The ventrolateral border of the main olfactory cavity (MOC) outpockets to form the lateral nasal groove. This runs longitudinally along the main olfactory chamber, and houses sensory cells of the vomeronasal organ (VNO). The nasolacrimal duct runs beneath the skin as a small canal, and joins the lateral nasal groove. The olfactory epithelium of the MOC is ridged, or striped, with strips of sensory and supporting cells set between raised ridges of respiratory epithelium. In aquatic adults, the respiratory epithelium is covered with long, presumably motile cilia. The olfactory epithelium has much shorter cilia. In contrast, terrestrial animals almost completely lack cilia on the ridges of non-sensory epithelium of the MOC, and the ridges are much more pronounced. The respiratory epithelium of the lateral nasal groove is ciliated in both aquatic and terrestrial forms, with long, thick, presumably motile cilia, while the vomeronasal epithelium has shorter, more slender cilia. Changes in epithelial characteristics between aquatic and terrestrial forms have also been reported in European newts (Lissotriton, Triturus) by Matthes (1926), and in Asian newts (Cynops) by Shibuya and Takagi (1963), though differing in detail from those in Taricha. This transition in morphology between media likely indicates a change both in olfactory mechanism and in sensitivity to chemical cues from conspecifics, as T. granulosa move between water and land as part of their annual reproductive cycle.

POS1-3  7:30 pm  Location specific protein expression and cell proliferation in the central nervous system following tail loss in the gecko (Reptilia: Squamata). Gilbert EAB, University of Guelph; McDonald RP, University of Guelph; Vickaryous MK*, University of Guelph
Abstract: Reflexive tail loss, or caudal autotomy, is common to many species of lizards. Tail loss is typically followed by tail regeneration, a spontaneous morphogenetic program that gives rise to a replacement appendage. Although tail regeneration is a growing topic of biological and biomedical interest, less is known about the effects of tail loss on other tissues of the body. Here, we present new data demonstrating that populations of cells lining the ventricular system of the brain and spinal cord in the leopard gecko (Eublepharis macularius) respond differently to tail loss. Prior to autotomy, both ependymal cells of the spinal cord and periventricular cells lining the lateral ventricles of the brain are slow-cycling (bromodeoxyuridine label retaining) and express markers characteristic of neural stem/progenitor cells (NSPCs), including the transcription factor Sox2. However these two populations are distinct, with only periventricular cells expressing the neuronal markers HuC/D and NeuN prior to tail loss. Caudal autotomy ruptures the spinal cord and triggers changes in protein expression and proliferative activity. Among ependymal cells, tail loss initiates an increase in cell proliferation, changes in NSPC protein expression, and an up-regulation of HuC/D (but not NeuN). Conspicuously, proliferative activity of periventricular cells within the brain decreases during the same timeframe. Our data reveals location specific variation in the wound-mediated response of the central nervous system following tail loss. Grant sponsor Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 400358 (MKV).

POS1-5  7:30 pm  Subterranean specialization of the ear morphology in Eospalax fontanierii (Rodentia: Spalacidae). Plestilova L*, Department of Zoology, Faculty of Sciences, University of South Bohemia, Ceske Budejovice 37005, Czech Republic; Hrouzkova E, Department of Zoology, Faculty of Sciences, University of South Bohemia, Ceske Budejovice 37005, Czech Republic; Hua LM, College of Pastoral Agriculture Science and Technology, Lanzhou University and Gansu Grassland Ecological Research Institute, Lanzhou 730020, Gansu, China; Burda H, Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, D-45117 Essen, Germany; Sumbera R, Department of Zoology, Faculty of Sciences, University of South Bohemia, Ceske Budejovice 37005, Czech Republic
Abstract: Acoustic conditions in the burrow systems of subterranean mammals are very special in comparison with the aboveground. The sound waves are spread only for short distances in the subterranean systems, best transmitted sounds are those of low frequencies. Moreover, there is high level of background noise. We can observe high level of specialization to the acoustic environment in mammals which inhabit this ecotope permanently. They are characterized by low hearing sensitivity and by shifting of their hearing range towards low frequencies. These adaptations are mirrored also in the ear morphology. Fossorial species, which are active also aboveground, are less specialized than strictly subterranean. Family Spalacidae is suitable taxon for studying of subterranean adaptations in the ear morphology, because it consists of species with different levels of specialization to this environment. It includes strictly subterranean species such as genus Spalax as well as species with large amount of aboveground activity such as genus Rhizomys. There are few studies on middle ear of this family which are focused on this topic, but there is a lack of studies dealing with the inner ear. In our study we attend to middle and inner ear of plateau zokor (Eospalax fontanierii) and the level of its subterranean specialization. It is considered as subterranean species, but according to its appearance and the field observation we expect lower level of specialization than in subterranean blind mole rat (Spalax fontanierii).

POS1-7  7:30 pm  Vomeronasal organ development in the sand lizard (Reptilia: Squamata: Lacertidae: Lacerta agilis). Tytiuk O, Lesya Ukrainka Eastern European National University, Faculty of Biology, Department of Zoology; Hrubyi V*, Lesya Ukrainka Eastern European National University, Faculty of Biology, Department of Zoology; Yaryhin O, I. I. Schmalhausen Institute of Zoology National Academy of Science of Ukraine, Department of Evolutionary Morphology of Vertebrates,; Stepanyuk Y, Lesya Ukrainka Eastern European National University, Faculty of Biology, Department of Zoology
Abstract: Olfactory system of tetrapods is anatomically and functionally divided into the main and accessory (vomeronasal) systems. There is no single opinion about the causes of vomeronasal system appearance. Earlier it was thought that it firstly appeared in tetrapods as an adaptation for terrestrial life. However, modern studies have shown that it appeared already in aquatic tetrapods. As the reptiles are the most primitive true land vertebrates, the developmental studies of vomeronasal system should shed light on its adaptation for the true terrestrial life. In the present study, we have investigated the development of the vomeronasal organ in the sand lizard. We have found that olfactory organ undergoes 4 stages of morphogenesis: 1) olfactory placode; 2) olfactory pit; 3) olfactory sac; 4) olfactory cavity. Division of the olfactory organ into two distinct parts starts with a medial invagination of the olfactory sacs, thus the rudiment of the vomeronasal organ appears. Later in ontogeny, vomeronasal organ becomes separated from the olfactory cavity and forms its own duct which opens into the oral cavity. At the same time, the medial and lateral edges of the olfactory sacs become fused in the middle part, thus olfactory sac receive two openings. The anterior opening represents nares and posterior one represents choanae. In comparison to amphibians, the early development of the vomeronasal organ in lizards is similar, however in lizards, at the later stages vomeronasal organ becomes completely separated from the main olfactory system. We assume that such anatomical differences could represent that in true terrestrial vertebrates vomeronasal organ received a new functional significance.

POS1-9  7:30 pm  Gross Anatomical Brain Region Approximation (GABRA): a new landmark-based approach for estimating brain regions in archosaurs. Morhardt AC*, Department of Biological Sciences, Ohio University; Ridgely RC, Department of Biomedical Sciences, Ohio University; Witmer LM, Department of Biomedical Sciences, Ohio University
Abstract: Studying brain evolution in extinct taxa can be challenging due to a lack of close correspondence between the brain and the endocranial cavity. Cranial endocasts may be faithful brain proxies in certain groups (mammals, birds) due to relatively complete filling of the cavity with neural tissue in life. However, the brain does not fill the endocranial cavity in adult non-avian archosaurs, making their endocasts less reliable indicators of brain size and shape. As such, previous studies of relative brain size and evolution in archosaurs relied on untested assumptions about brain-endocast fidelity. We propose a new approach known as Gross Anatomical Brain Region Approximation (GABRA), which involves importing a digital endocast, derived from CT scanning and 3D visualization software, into modeling software (Maya). In Maya, brain regions underlying the endocast are modeled as 3D polygons, the limits of which are based on osteological correlates of soft-tissue structures that are 1) identified by comparison with extant taxa, and 2) visible reliably on endocasts. Discernible correlates for soft-tissue structures (e.g., neurovascular canals, dural sinuses, fossae formed by the brain itself) serve as landmarks that inform the location and size of general brain regions (e.g., cerebral hemispheres, cerebellum, optic lobes, olfactory bulbs). Together, landmarks form a set of explicit criteria used to assess endocasts and model brain regions. GABRA criteria and resulting brain models were validated in extant diapsids (lizards, snakes, alligators, birds) via literature review, gross dissection, CT scanning of iodine-stained specimens, and MRI studies. Therefore, GABRA models produced for extinct archosaurs are credible. Ultimately, GABRA permits moving beyond consideration of the cranial endocast as a singular entity to studying the evolution of the archosaur brain and its different parts, allowing hypotheses of brain-region evolution to be tested.

POS1-11  7:30 pm  The skull and endocranial anatomy of the extinct giant moa Dinornis robustus (Aves: Palaeognathae) and implications for the behavioral role of vision in moa. Early CM*, Ohio University; Ridgely RC, Ohio University; Porter WR, Ohio University; Cerio D, Ohio University; Witmer LM, Ohio University
Abstract: Moa comprise a group of extinct flightless birds from New Zealand belonging to Palaeognathae, a basal neornithine group that includes both flighted (e.g., tinamous, lithornithids) and flightless members (e.g., ratites such as ostriches, etc.). The skull bones of a South Island giant moa (Dinornis robustus, FMNH PA 35) were CT scanned to study its skull structure and endocranial anatomy. Internal structures such as the brain endocast and inner-ear labyrinth were virtually reconstructed using Avizo. Similar analyses were done for all extant palaeognath clades, as well as for Lithornis. Whereas much of the endocast of D. robustus is conservative, some apomorphies in its visual system may have implications for inferring sensory abilities. For example, the optic tectum, which is the major retinorecipient structure in the avian brain, shows marked reduction compared to that of other palaeognaths, and is located rostral to the trigeminal nerve trunk as opposed to dorsal to this structure as in other palaeognaths. Another surprising finding is that the floccular lobe of the cerebellum was absent, despite being moderately well-developed in other palaeognaths. The highly reduced flocculus in moa could have implications for their behavior, as this structure is intimately connected to the visual apparatus via the vestibulo-ocular reflex. Finally, the bony orbit itself is small relative to skull size compared to other palaeognaths, indicating a relatively small eyeball and potentially affirming reduced reliance on vision. However, previous authors failed to find a significant difference between moa and other palaeognaths in optic foramen and Wulst size, two characteristics that have been used as proxies for visual capabilities. Despite the apparent conservation of these two characters, the reduction in the suite of other neuroanatomical structures associated with vision strongly suggests a diminished importance of visually-driven behaviors in this clade.

POS1-13  7:30 pm  Neuroanatomy of the extinct terror birds (Aves: Phorusrhacidae): implications for a predatory mode of life. Degrange FD, CONICET - Universidad Nacional de Córdoba, Argentina; Tambussi CP, CONICET - Universidad Nacional de Córdoba, Argentina; Ridgely RC, Ohio University; Witmer LM*, Ohio University
Abstract: Terror birds (Cariamiformes, Phorusrhacidae) are a completely extinct group of ground birds that comprise one of the most remarkable and diverse groups of the South American Cenozoic avifauna. Widely considered to have been apex predators, their basic habitus of being running predators has never been questioned for most of their species. Details about their predatory abilities, however, particularly with regard to prey detection behaviors, require more in-depth study. Here we present for the first time the morphology of the brain and vestibular apparatus of a diversity of terror birds based on high-resolution computed tomographic (CT) scans from which we constructed digital brain endocasts. Four taxa comprised the sample, including the mesembriornithine Llallawavis scagliai, the psilopterine Psilotperus lemoinei, the patagornithine Patagornis marshi, and the giant phorusrhacine Kelenken guillermoi. Comparison with other birds, such as extant raptorial and cursorial birds, sheds light on the adaptation to a terrestrial and cursorial predatory lifestyle. The enlarged Wulst (eminentia sagittalis, hyperpallium), the well-developed optic lobes, the large optic nerves, and large apparent eyeball size indicate that all terror birds were very visual birds, capable of handling large visual input. Moreover, the long and slender semicircular canals of the inner ear labyrinth suggest not only agility but also highly coordinated eye, head, and neck movements. The sense of smell, on the other hand, was not well developed in terror birds, as judged by the very small size of the olfactory bulb, which is consistent with a lifestyle as an active pursuit predator rather than as a more obligate scavenger. The consistent picture that emerges based on the neuroanatomical structure of these terror birds is that prey detection was based mainly on vision and during pursuit they were able to make agile, sudden, and fast movements to chase and subdue prey.

Locomotion (LOC)
POS1-15  7:30 pm  Muscle function in rainbow smelt, Osmerus mordax, during winter. Coughlin DJ*, Widener University; Bradley MA, Widener University; Shuman JL, Widener University
Abstract: Rainbow smelt (Osmerus mordax) display an impressive ability to acclimate to very cold water temperatures. These fish express anti-freeze proteins, glycerol and additional osmolytes in their plasma, liver, muscle and other tissues to avoid freezing at sub-zero temperatures. In turn, smelt must feed actively in winter to maintain osmolyte levels. We explored smelt muscle function in winter through thermal acclimation studies on smelt swimming performance, muscle contractile properties and muscle protein expression. The thermal acclimation studies demonstrated a strong influence of cold acclimation on swimming performance, with cold acclimated fish able to swim at higher sustained swimming speeds but at perhaps higher energetic costs than warm acclimated fish. Cold-acclimated smelt had faster muscle contractile properties in both their fast- and slow-twitch myotomal muscle, with cold-acclimation associated with shorter relaxation times, faster maximum shortening velocity and increased power output. In addition, muscle from cold-acclimated fish displayed reduced thermal sensitivity to decreasing temperature in muscle mechanics experiments. Immunohistochemistry and dot blot analysis indicate shifts in muscle myosin heavy chain content. Quantitative PCR confirms a change in myosin gene expression with thermal acclimation. RNA-Seq suggests changes in the expression of genes for a variety of muscle proteins and for metabolic pathways associated with glycerol production. An integrative approach has revealed an impressive thermal acclimation by rainbow smelt that permits muscle function and active locomotion at sub-zero temperatures.

POS1-17  7:30 pm  Scaling of burial mechanics in the English sole, Parophrys vetulus (Actinopterygii: Pleuronectiformes). Corn K.C.*, Cornell University; Farina S.C., Harvard University; Gibb A.C., Northern Arizona University; Summers A.P., University of Washington
Abstract: The size of an organism influences its interactions with the environment, and the study of these interactions over a range of sizes (scaling) is key to understanding limits of performance in large and small fishes. Flatfishes (Pleuronectiformes) rapidly bury themselves under sediments using body undulations and fin movements. This burial behavior forces the fish to interact with both the fluid environment and a granular medium and is acutely affected by size of the organism. The fish must fluidize a volume of the substrate in a manner that distributes it over the entire surface of the body when it falls. We used the English Sole, Parophrys vetulus, as a model to explore the effects of scaling on burial. We recorded burial events from 15 fish across a size range (5 to 30 cm), keeping sand grain size consistent, using high speed video at 250 fps and determined undulation frequency, time to burial, and percent body coverage. We found that larger fishes bury more slowly and with a lower undulation frequency, but sediment coverage was not affected by the size of the fish. We then used 5 individual fish of the same size (5.7 – 8.1 cm) and changed the size of the sediment (125 – 710 microns) and found that grain size does not affect the undulation frequency or time to burial of small fish, but they do lose coverage on media of increased size relative to fish size. We propose that this is because the small fish cannot fluidize sand of larger grain sizes as effectively. Our results indicate that kinematics of flatfish burial are a function of fish size, and the success of the behavior is affected by the relative grain size of the sediment.

POS1-19  7:30 pm  How to modify a fin into a limb: Insights from anglerfish. Dickson BV*, Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard; Pierce SE, Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard
Abstract: The evolution of tetrapod limbs from fish fins is one of the most-studied anatomical transitions in vertebrate evolution. However, tetrapods are not the only group of fish to have modified their fins into functional limbs. Various other vertebrate groups have adopted limb-like fins in order to navigate their environment, including epaulette sharks, mudskippers, and anglerfish. Of these groups, anglerfish (Lophiiformes), and particularly the charismatic frogfish (Antennariidae), have modified their pectoral fins into perhaps the closest functional analogue to a tetrapod limb – with joints that are similar to the shoulder, elbow, and wrist (including digit-like fin rays). Frogfish use these ‘limbs’ for station-holding and for active substrate-driven locomotion using one of two ‘gaits’. In the first, they move their pectoral fins in an alternating fashion, propelling themselves forward like a two-legged tetrapod, without use of the pelvic fins. Alternatively, they can progress with a slow gallop by moving their pectoral fins synchronously back and forth, transferring their weight to the pelvic fins during the swing phase of pectoral movement. Here we examine the musculoskeletal anatomy of the frogfish pectoral fin, compare it to the morphology of closely-related pelagic anglerfish, and isolate the underlying structural modifications which permit frogfish to use their fins as limbs. Hard and soft tissue anatomy was captured through contrast-enhanced µCT scanning using Phosphomolybdic Acid (PMA) and the skeletal and muscular elements were virtually dissected to create high-resolution 3D musculoskeletal reconstructions. Through these 3D models, we trace the anatomical scaffolding underlying the frogfish pectoral fin and make correlations with its unique locomotor behaviors – thus providing a deeper understanding of this functionally convergent fin-limb complex.

POS1-21  7:30 pm  Simulating movement in early tetrapods: inputs from limb muscle physiology. Pierce SE*, Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA; West TG, Structure and Motion Lab, Department of Comparative Biomedical Sciences, The Royal Veterinary College, UK; Hutchinson JR, Structure and Motion Lab, Department of Comparative Biomedical Sciences, The Royal Veterinary College, UK
Abstract: One of the great mysteries regarding the evolution of animals is how and when tetrapods achieved the ability to stand and move on solid ground. But, which pioneering tetrapod species could move on land and how well? Our past work inferred that the morphology of Devonian stem tetrapods could not have supported walking in a typical salamander-like fashion and that a mudskipper-like crutching gait was more likely to be employed. Such a hypothesis means we still know very little about the evolution of modern walking behaviours. To further our investigation, we aim to reconstruct dynamic motions in a series of early tetrapods bracketing the water-to-land transition using modern computer simulation techniques; however, such simulations depend on input data from relevant extant taxa. Here we present new measurements of the in vitro mechanical properties of isolated, intact forelimb (FL, n=10) and hindlimb (HL, n=14) muscles from adult fire salamanders (Salamandra salamandra), tested at 20°C under near maximal activation. Whole muscle cross-sectional area (CSA) ranged from 0.1–1.8 mm2 across the two FL and three HL muscles tested. CSA-dependent maximal force (mN) was the same in FL (y=240x, r22=0.6) and HL (y=229x, r2=0.56) muscles. Similarly, peak power (µW) was related to muscle volume (mm3) across the two muscle groups (y=92x, r2=0.4). Mean (±SEM) maximal isometric stress (in kPa; 243±8 for FL and 234±6 for HL), peak power (in watts per litre; 93±3 for FL and 98±3 for HL) and Vmax (in muscle-lengths per second; 4.5±0.1 for FL and 5.5±0.1 for HL) were statistically indistinguishable for the two muscle groups. In addition, shortening speed at peak power (Vopt) was similar for FL and HL, being 27-28% of Vmax. Hence, a "generic" set of muscle properties are likely applicable to biomechanical models of S. salamandra movements at 20°C, which helps inform future analyses of extinct tetrapod species.

POS1-23  7:30 pm  Why are long bones curved? Milne N*, University of Western Australia   nick.milne@
Abstract: The presence of curvature in long bones has long puzzled scientists. The curvature would seem to make the bone less able to bear longitudinal loading. Recently, a novel hypothesis has been presented that suggests the bone is curved to resist its habitual loading. A striking example of a curved bone is the radioulna of obligate quadrupeds which has a caudal curvature (concave caudally). The radioulna in these species is a lever operated by the triceps muscle which tends to bend the bone in a cranial direction. The caudal curvature provides a mechanism whereby cranial bending strains induced by the action of triceps can be resisted by longitudinal and flexor muscle forces which produce caudal bending strains. This idea has been tested by comparing the performance of a curved radioulna with that of a straightened model of the same bone. This paper explores the generality of this idea by examining other curved long bones in vertebrates. In particular, arboreal species that use their (radio)ulna for prehension are considered. Here the habitual loading is provided by the brachialis muscle which introduces caudal bending strains, and it is predicted that, according to the novel hypothesis to explain curved bones presented here, these bones should have a cranial curvature – this is found to be the case and so, to be consistent with the predictions of the hypothesis. This begs the question of how bone curvatures develop. The hypothesis presented also leads to a possible explanation.

POS1-25  7:30 pm  Tendinous system in Leptodactylus (Amphibia, Anura, Leptodactylidae): Morphological diversity and its relation to habitat and locomotion. Fratani J*, CONICET-Fundación Miguel Lillo; Ponssa ML, CONICET-Fundación Miguel Lillo; Abdala V, Instituto de Biodiversidad Neotropical UNT-CONICET
Abstract: Tendons can be characterized as fibrous connective tissue with the main function of connecting and transmitting force from muscles to bones, with a unique structure, physiology and developmental origin which allow their consideration as an independent system. Despite of their anatomical and functional singularities, a description of the tendinous system is still not available for anurans. Herein, we present a general categorization of the tendinous system of the most superficial surface of Leptodactylus latinasus using techniques of comparative anatomy. Leptodactylus encompasses species with gradual independence of water and different locomotor modes, so we test for the relation of these ecological features with morphometric data of tendons using comparative analysis, and optimize qualitative data. We compared the tendinous pattern of L. latinasus with 44 species of leptodactylid frogs. Morphometric and qualitative data were taken from the origin and insertion tendons of the following muscles: longissimus dorsi, coccygeous sacralis, iliacus externus, iliofibularis, sternoradialis, triceps, and flexor digitorum communis. The main tendinous areas were found on the girdle region and limb articulations. All log10-transformed variables showed highly significant phylogenetic signal (p<0.001). Pagel’s lambda values were equal or higher than 0.89, therefore the phylogenetic effect is high in this database. There was no significant relation between morphometric data and ecological characters, however the optimization of qualitative caracters showed a relation between the shape of the origin tendon of the iliacus externus and species with digging locomotor modes.

POS1-27  7:30 pm  Does crocodilian ankle morphology relate to ankle kinematics? Suzuki DS*, Sapporo Medical University
Abstract: The functional morphology of the crocodilian ankle has been nearly neglected. The aim of this study is to clarify the relationship between ankle morphology and its kinematics in crocodiles. The ankle joint of crocodiles are consist of two joints: i.e., a crurotarsal joint and a mesotarsal joint. These two joints produce the dorsiflexion/plantarflexion and the eversion/inversion movements. To investigate ankle joint mechanisms, seven crocodylids and four alligatorids were CT scanned in five positions ranging from maximum dorsiflexion to plantar flexion. This movement was performed along the sagittal plane on the 2nd metatarsal axis. In addition, bone specimens were measured from 11 crocodylids and 14 alligatorids. The averages of total ankle ROM at the tibia-1st metatarsal were 59.9°-136.4° in the crocodylids and 57.6°-152.0°in the alligatorids, respectively. While the averages of ROM at the tibia-4th metatarsal were 52.7°-147.6° and 60.3°-162.8°, respectively. In osteological characters, the crocodylids have a large fibular facet, and wide 1st metatarsal. The standardized width of the 1st metatarsal was significantly greater in crocodylids than in alligatorids (p <0.01). The ROM analysis showed that the crocodylids are in eversion at dorsiflexion, while the alligatorids are almost in the neutral position. The crocodylids were considered to be mainly loaded on the first metatarsal because the crocodiles are in dorsiflexion at rest. This hypothesis is supported by the following osteological characters, i.e., a large fibular facet in the astragalus and a wide first metatarsal. In crocodylids, most of the load of the fibular side will be takes by the astragalus and first metatarsals, whereas that load will be taken more by the calcaneum in alligatorids. The present study suggested crocodylids and alligatorids evolved a different morphology of the ankle joint, and it has been associated with ankle movement.

POS1-29  7:30 pm  Investigating inter-limb evolutionary linkages in avian limb proportions. Proffitt JV*, The University of Texas at Austin
Abstract: Modern birds are the most diverse terrestrial vertebrates, displaying notably higher variability in ecology and locomotor behavior than their non-avian theropod relatives. It is hypothesized that a functional shift in the forelimb and hind limb during the early evolution of birds, with the forelimb co-opted for flight freeing the hind limb from functioning solely in terrestrial locomotion, played a role in facilitating this radiation. Specifically, differential evolution between these “locomotor modules” enabled a greater diversity of ecological and behavioral options for birds. A connection between these separate limb locomotor modules and ecomorphological diversity in birds is supported by greater diversity in forelimb and hind limb proportions in extant bird lineages relative to non-avian theropod dinosaurs. Evolution in one “module” will likely affect evolution in another due to functional tradeoffs related to properties of the whole organism such as ecology and behavior. Avian forelimb and hind limb proportions have been independently studied in relation to habitat, flight style, scaling, and intra-limb developmental integration, but little is known of how limb morphospace evolved through time in different avian lineages. Furthermore, potential functional tradeoffs inducing concomitant evolution in forelimb and hind limb proportions remain uncharacterized and uninvestigated across Aves. I report on the evolutionary tempo and mode of forelimb and hind limb proportions in 495 species of birds in a phylogenetic framework. I examine how limb proportions vary across clades when accounting for body size and relatedness. Additionally, I compare the evolution of forelimb and hind limb proportions and investigate whether or not shifts in the proportions of one set of limbs predictably result in modification to the other set, testing whether or not the nature of these potential evolutionary linkages can be correlated to factors such as ecology and locomotor behavior.

POS1-31  7:30 pm  Sciuromorph limb bones: morphological correlates to different locomotor behaviors. Woelfer J.*, Humboldt U. Berlin; Nyakatura J. A., Humboldt U. Berlin
Abstract: Sciuromorph rodents are highly diverse in their habitat related locomotion, due to the varying extents and intermixture of aerial, arboreal, scansorial, cursorial and semi-fossorial lifestyles. We aim to find out, how sciuromorph locomotor behavior is correlated with morphology of the scapulae and femora, i.e. the limb elements whose motion has the biggest impact on propulsion during horizontal locomotion. Previous investigations suggest ecomorphological differences in attachment sites of internal and external retractor and abductor muscles. Climbing upside-down may demand for larger shoulder-extending protractor muscles and hence increased attachment sites in arboreal species. We use geometric morphometrics to analyze the complex shape of these limb elements. Bones from approximately 150 species are investigated, housed at various museum collections of Europe and North America. Detailed surface models are obtained using a surface laser-scanner or a µCT to allow a three-dimensional analysis. Scapulae are photographed from different geometrically predefined perspectives for multiple two-dimensional analyses. A preliminary qualitative evaluation of photos and scans supports ecomorphological differences in muscle attachment sites. The scapula of arboreal species tends to have a relatively bigger attachment site for the teres major. Regarding the femur, arboreal species appear to have a relatively larger third trochanter, which serves as an attachment site for the gluteus maximus. These muscles may serve as whole limb or limb element retractors in agreement with increased demand for powerful retraction during vertical climbing against gravity. Yet, we observe exceptions to these observations indicating the need of a rigorous quantitative analysis.

POS1-33  7:30 pm  Kinematics of arboreal descent in primates. Perchalski BA*, Duke University
Abstract: Arboreal primates must often descend steep supports. Head-first descent gives an animal the advantage of being able to view its path ahead, but has the disadvantages of increasing load on the forelimbs and the risk of forward pitch. Previous research on primates shows that they mitigate increased force on the forelimb during declines through the use of protracted limbs, altered gait, and reduced speed. However, nothing is known about the mechanics of tail-first descent, or the influence of substrate orientation, body mass, and intermembral index (IMI) on descent posture. The present study tests the hypothesis that as steepness increases the proportion of head-first descents will decrease in favor of alternate means of travel (e.g. leaping, tail-first descent). Three strepsirrhine primate species, Eulemur coronatus (n = 4; species mean body mass (BM) = 1.6 kg; IMI = 69), Varecia variegata (n = 4, BM = 3.5 kg; IMI = 72), and Nyticebus pygmaeus (n = 2; BM = 0.3 kg; IMI = 88), were videorecorded moving between two platforms connected by a thin diameter, 1.8 m long support held at 0° (horizontal), 30°, 60°, and 90° (vertical). Frequency of descent methods, changes in speed, and limb angles were calculated and compared by angle of support orientation. Head-first descent was observed in all conditions, with a gradual decrease in use as slope increased in all species. During 90° descent, E. coronatus used head first descent in an average of 23.5% of cases, V. variegata in 69.5%, and N. pygmaeus in 62.5%. IMI appears to be a better predictor of head-first descent frequency than body mass; this relationship will be further studied with additional species. These results contribute to a better understanding of how tradeoffs in locomotor specializations and anatomy influence navigation of complex arboreal environments by primates.

POS1-35  7:30 pm  Form-function relationships and the evolution of arboreal locomotion in mammals. Herrel A*, MNHN Paris; Böhmer C, MNHN Paris; Fabre A-C, MNHN Paris; Herbin M, MNHN Paris; Cornette R, MNHN Paris; Peigné S, MNHN Paris
Abstract: Almost all mammalian orders have arboreal representatives. The adaptation to life in a three-dimensional arboreal environment has been acquired independently in the different lineages. However, an arboreal lifestyle needs to be clearly distinguished from arboreal locomotion. The latter implies that the locomotor performance of the animal is challenged by the discontinuous nature and complexity of the arboreal substrates. Two eutherian lineages are exceptional in this regard because they evolve relatively large body sizes, display different mechanisms for arboreal locomotion, and have an excellent fossil record: Carnivora and Primates. Arboreal locomotion imposes selective pressures that may affect the anatomy of the appendicular skeleton as the limbs have to be mobile to reach across discontinuities yet at the same time need to be able to generate a firm grip. The present project aims at better understanding the relation between bone shape and the muscular anatomy of the appendicular skeleton in the context of arboreal locomotion. The functional properties of the forelimb muscles in carnivores and primates will be described and related to quantitative analyses of limb bone morphology using PLS analyses. This comparative study will shed light on the functional adaptations of the forelimb associated with arboreal locomotion. The results will provide better insights into the functional link between limb structure and locomotion mechanics and will improve our inferences of function and behavior in fossils.

POS1-37  7:30 pm  Functional implications of manual grasping strength in marmosets (Primates: Callithrix jacchus) and squirrel monkeys (Primates: Saimiri boliviensis). Young JW*, Northeast Ohio Medical University (NEOMED); Chadwell BA, Northeast Ohio Medical University (NEOMED); O'Neill TP, Northeast Ohio Medical University (NEOMED); Patel BA, University of Southern California
Abstract: Grasping supports via the powerful flexion, adduction and opposition of the autopodial digits is a critical performance demand for many arboreal tetrapods, from tree frogs to primates. Functionally, grasping appendages are thought to permit arboreal animals to maintain purchase and exert torques around the support, thereby promoting stability. In this study, we test the association between grasping performance and narrow-branch arboreality by quantifying grasping strength and digit robusticity in two closely-related New World monkeys - marmosets (Callithrix jacchus) and squirrel monkeys (Saimiri boliviensis). Whereas squirrel monkeys typically feed and travel quadrupedally in a fine-branch niche, marmosets are devoted gumnivores that primarily forage on vertical tree trunks. We therefore predicted grasping forces and digital robusticity should be significantly greater in Saimiri. We used a custom-constructed grip force transducer to measure hand grasping strength (Saimiri: 48 trials; (Callithrix: 82 trials; n = 2 individuals per species), quantifying the maximum and average grip force exerted during each trial as a percentage of body weight (% BW). To test for a morphological correlate of grasping strength variation, we also quantified metacarpal cross-sectional section moduli (scaled to bone length) in museum samples. Maximum within-trial grasping forces were significantly greater in Saimiri (74% BW) than in Callithrix (59% BW) (p<0.001), as were average grasping forces (Saimiri: 46% BW; Callithrix: 27% BW; p<0.001). Correspondingly, Saimiri had stronger post-axial metacarpals (i.e., digits 3-5) than did Callithrix. Both stronger manual grasping forces and more robust post-axial digits likely facilitate safe and efficient locomotion when squirrel monkeys travel and forage above narrow-diameter branches. Supported by NSF (BCS-0959438, BCS-1126790, BCS-1317047), NEOMED, and USC.

POS1-39  7:30 pm  Functional anatomy of the nasal muscles in Japanese badger Meles anakuma (Mammalia: Mustelidae). Kobayashi M*, Okayama University of Science; Hosomi H, Okayama University of Science
Abstract: The infraorbital foramen in badgers is considerably larger than that in other Carnivora of similar body size. The morphology of the infraorbital foramen is an important characteristic for identification of badgers. Generally, the infraorbital foramen is a passage for the infraorbital nerve and vessels, and the surface of the infraorbital foramen is the origin of lip and nose muscles in many mammals. However, no anatomical studies have reported on the infraorbital foramen in badgers. Here we describe the nasal muscles around the infraorbital foramen and the infraorbital nerve and vessels, and we report on the function of the nasal muscles in the Japanese badger. The superficial muscle of levator nasolabialis muscle arises in the frontal region between the anterior surface of the orbit and the lateral surface of the maxillary bone. It inserts on the lateral side of the nasal and superior lip. The well-developed levator rostri muscle arises from the inside wall of the inferior orbital foramen and inserts on the subcutaneous tissue at the dorsal midline of the rhinarium. The levator rostri muscle is situated on the deep to the levator nasolabialis muscle. The distal part of the levator rostri muscle is tendinous. The infraorbital nerve and vessels are situated on the deep to the levator rostri muscle and reach the tip of the nose. The large infraorbital foramen in the Japanese badger is suitable for providing the origin for the well-developed the levator rostri muscle. Although the levator rostri muscle of the Japanese badger is an important muscle that elevate the nose, similar to that of other mammals, the morphology of the levator rostri muscle that arises from the inside wall of the infraorbital foramen showed a specific form in the Japanese badger.

POS1-41  7:30 pm  Thoracic strengths a new indicator of life reconstruction in extinct secondary aquatic mammals. Ando K, Graduate School of Environmental Studies, Nagoya University; Fujiwara S*, Nagoya University Museum
Abstract: Habitat-shifts from land to water have occurred independently in several mammal lineages. However, reliable life reconstructions of each extinct taxon remain difficult due to our little knowledge about the relationship between skeletal morphology and its function, and therefore, the timing of the shifts in their locomotor strategies and habitats are yet to be fully understood. We estimated the strengths of rib cages against vertical compression in approximately 30 extant and 4 extinct mammal specimens of three lineages of mammals (cetartiodactyls, paenungulates, and carnivorans) which include terrestrial-quadrupedal, semi-aquatic, and obligate aquatic taxa. Our analyses in the extant taxa showed that the strengths were high among terrestrial-quadrupedal/semi-aquatic taxa, whose rib cages are subjected to vertical compression during the support on land, whereas the strengths were low among obligate aquatic taxa, whose rib cages are not subjected to antigravity force in the water. We therefore propose the rib cage strength as a new index to estimate the ability of the terrestrial support by either the forelimbs or thoraces. Among the extinct taxa, the rib cage strengths of a basal cetacean (Cetartiodactyla: Ambulocetus) and two desmostylians (Paenungulata: Paleoparadoxia and Neoparadoxia) were as low as those of the extant obligate aquatic taxa. Based on our new index, these extinct mammals were not likely to move actively on land, though they have retained all four limbs. Further study on the rib cage strengths in extant/extinct semi-aquatic taxa may help understanding of the processes of ecological shifts in these groups.

Paleontology (PAL)
POS1-43  7:30 pm  Anatomy and diversity of the earliest fossil vertebrates (Chengjiang Biota, Cambrian, China): new evidence from experimental taphonomy. Murdock DJE*, University of Leicester, UK; Gabbott SE, University of Leicester, UK; Cong P-y, Yunnan Key Laboratory for Palaeobiology, Yunnan University, China; Purnell MA, University of Leicester, UK
Abstract: The oldest fossil vertebrates are from the Lower Cambrian Chengjiang biota of China, which contains four genera of fish-like, primitive vertebrates: Haikouichthys, Myllokunmingia, Zhongjianichthys and Zhongxiniscus. These fossils play key roles in calibrating molecular clocks and informing our view of the anatomy of animals close to the origin of vertebrates, potentially including transitional forms between vertebrates and their nearest relatives. Despite the evident importance of these fossils, the degree to which taphonomic processes have affected their anatomical completeness has not been investigated. For example, some or all might have been affected by stemward slippage – the pattern observed in experimental decay of non-biomineralised chordates in which preferential decay of synapomorphies and retention of plesiomorphic characters would cause fossil taxa to erroneously occupy more basal positions than they should. This hypothesis is based on experimental data derived from decay of non-biomineralised chordates under laboratory conditions. We have expanded this analysis to include a broader range of potentially significant environmental variables; we have also compared and combined the results of experiments from several taxa to identify general patterns of chordate decay. Examination of the Chengjiang vertebrates in the light of these results demonstrates that, contrary to some assertions, experimentally derived models of phylogenetic bias are applicable to fossils. Anatomical and phylogenetic interpretations of early vertebrates that do not take taphonomic biases into account risk overestimating diversity and the evolutionary significance of differences between fossil specimens.

POS1-45  7:30 pm  Morphology of two early fossils aligned with the specialized deep-sea predatory fish groups Gempylidae and Trichiuridae assessed using micro-computed tomography. Beckett H*, University of Oxford; Johanson Z, Natural History Museum, London; Friedman M, University of Oxford
Abstract: Gempylids (snake mackerels) and trichiurids (cutlassfishes) are pelagic fishes characterized by slender to eel-like bodies, deep-sea predatory ecologies, and large fang-like teeth. Several hypotheses of relationships between these groups have been proposed, but a consensus remains elusive. Fossils attributed to gempylids and trichiurids consist almost exclusively of highly compressed body fossils and isolated teeth and otoliths. Two three-dimensional crania from the London Clay of England join these remains. Identified as Eutrichurides and Progempylus, these taxa are 53 million years old and represent some of the oldest fossils aligned with Gempylidae and Trichiuridae. We applied computed tomography in order to clarify structure in these potentially critical taxa. Eutrichuirides bears large premaxillary fangs, found in trichiurids, gempylids, and scombrolabracids. Apart from the jaws and hyoid arch, this specimen is highly fragmented. However, features of the vomer apparent in CT data but not visible externally suggest a closer relationship with trichiurids. By contrast, Progempylus preserves a braincase, gill skeleton, suspensorium, and lower jaw, but lacks the upper jaws. It shows a mosaic of apparently derived features with a restricted distribution among gempylids (e.g., a single or pair of teeth on vomer) or trichiurids (e.g., short posterodorsal process of quadrate), and its placement remains unclear. Uncertainties relating to the phylogenetic positions of these critical early taxa reflect conflicting hypotheses for the relationships of modern species. Trichiurids are reliably resolved as a clade, but gempylids are more problematic. Most analyses report gempylid paraphyly, either with respect to trichiurids or a set of lineages classically identified as ‘scombroids’. Ongoing assessment of the relationships of extant gempylids, trichiurids and related families aims to identify the placement of these fossils among living groups.

POS1-47  7:30 pm  Early Permian amphibamid Pasawioops (Amphibamidae, Dissorophoidea): An ontogenetic series. Atkins J B*, Carleton University; Reisz R R, University of Toronto Mississauga; Maddin H C, Carleton University
Abstract: Amphibamids (Temnospondyli: Dissorophoidea) were small, amphibian taxa that were mostly present during the Early Permian (~270 to 300 Mya). These taxa are generally considered to be close relatives of modern amphibians (lissamphibians). Thus, detailed analysis of their morphology and phylogenic relationships sheds light on the evolution of lissamphibians and the origin of several unique traits. Amphibamids are additionally interesting because for some taxa larval, juvenile and adult specimens have been found, allowing researchers to discern the ontogenetic progression of morphological traits. However, because many amphibamids have a more juvenile appearance than other amphibians (e.g. comparatively large orbits and small body size), distinguishing between ontogeny dependent traits and diagnostic traits of taxa is of utmost importance. The goal of the present research is to first document the detailed morphology of the skull of the recently described amphibamid Pasawioops (OMNH 73019) using novel CT data, and to second explore the nature of ontogeny dependent traits in this taxon through comparison with a recently referred specimen of Pasawioops (MCZ 1415). We found the smaller OMNH 73019 specimen differs from MCZ 1415 in the following traits: the skull bones are not as tightly sutured, the anterior skull has a more rounded appearance, and the jaw articulations do not extend as far posteriorly beyond the occiput. Together, these data indicate that OMNH 73019 likely represents a more juvenile specimen of Pasawioops and the observed differences between specimens are consistent with previously posited juvenile traits in amphibamids. This suggests the nature of ontogeny dependent traits may be more conserved across Amphibamidae than previous thought.

POS1-49  7:30 pm  Phylogeny, ecology, and time: 2D outline analysis of anuran skulls from the Early Cretaceous to Recent. Bardua C*, University College London; Evans SE, University College London; Goswami A, University College London
Abstract: Anura have a long fossil record spanning from the early Jurassic to Recent. However, even the best-preserved specimens are often severely flattened, limiting their inclusion in quantitative analyses of anuran morphological evolution. Here we perform a 2D morphometric analysis of anuran skull outlines obtained from the published literature, incorporating 42 Early Cretaceous to Miocene species, as well as 93 extant species in 32 families. Outlines were traced in tpsDig2 and analysed with elliptical Fourier analysis in the R package ‘Momocs’. Fourier coefficients were used as high dimensional variables in MANOVAs and disparity analyses across multiple ecological and life history groupings, such as region, habitat, and developmental strategy. As skull outlines showed significant phylogenetic signal (k=0.53, p=0.006), phylogenetic MANOVAs, using composite phylogenetic trees from recent published analyses, were also conducted. The Neotropical realm shows higher disparity than the Australian, Palearctic and Oriental realms (p=0.007, 0.013, 0.038, respectively), suggesting concordance of disparity and diversity. Developmental strategy had a weak effect on skull shape (R2=0.02, p=0.039), and disparity was similar in metamorphosing and direct developing frogs. Ecological niche was a significant discriminator of skull shape (F=1.44, p=0.004), but not after phylogenetic correction. Body size is strongly associated with differences in skull shape in fossil frogs (R2=0.44, p=0.017), and to a lesser extent, in extant taxa, (R2=0.10, p=0.049), and this effect is only partly due to allometry, which is weak but significant in both fossil (R2=0.11, p=0.002) and extant frogs (R2=0.09, p=0.001). Finally, morphospace occupation of anuran skull outlines has changed over time, as skulls binned in 5-million year bins based on first occurrence date showed significant differences in morphospace position (F= 2.42, p=2.2e-16).

POS1-51  7:30 pm  New skull material of the Early Permian Eryops from Brushy Creek (Wichita Group, Texas) showing the morphological variability of foramina and canals in the quadratojugal of basal tetrapods. Klembara J.*, Comenius University in Bratislava; Cernansky A., Comenius University in Bratislava; Witzmann F., Museum für Naturkunde Berlin; van Heteren A., Universität Bonn, Germany
Abstract: Eryops is an important representative of Permo-Carboniferous basal tetrapods and one of the best-known large temnospondyl amphibians of this period. This taxon forms a significant component of the Early Permian tetrapod fauna of Texas and New Mexico and here we report on a new undescribed record from Brushy Creek in Texas (Petrolia Formation, Wichita Group; Lower Permian - lower Artinskian). Our material, found in 2015, consists of a partial left mandible, a left nasal, a jaw fragment (premaxilla or maxilla), and left quadratojugal fragments. We used computed tomography methods (CT) for imaging both internal and external structures, for the first time for Eryops. The quadratojugal presented here is exceptional compared to all known basal tetrapods in having four different internal foramina. CT data have shown that these foramina are interconnected by canals within the bone. This indicates that the morphology of the foramina and the course of the canals in the quadratojugal of basal tetrapods is more variable than hitherto thought.

POS1-53  7:30 pm  The description of the axial osteology of a juvenile plesiosaur, and revision of polycotylid systematics. Morgan DJ*, Marshall University ; O'Keefe FR, Marshall University
Abstract: The polycotylid’s were a clade of plesiosaurs that proliferated during the Cretaceous period of the Mesozoic. The clade became very speciose during the late Cretaceous, and there is speculation that the high species diversity is a relic of the lack of information on ontogeny and intraspecific variation within the polycotylids, since most species are only represented by one fossil specimen. To answer the question of whether the late Cretaceous polycotylids featured high species diversity, ontogeny must be accounted for within the polycotylid clade. The presence of juvenile plesiosaurs in the fossil record are rare, and ontogenetic growth series for plesiosaur taxa remain speculative. The axial osteology of the juvenile polycotylid from the Wallace Ranch was described, and a reconstruction of its skull has been made. The juvenile Wallace Ranch skull provides insight into the cranial development of an immature plesiosaur, and from this specimen, allometric growth patterns of the cranial bones for polycotylids will be evaluated. The juvenile and the adult specimen, along with all the other polycotylid species were evaluated via a phylogenetic analysis, in an attempt to illuminate the relationships between the taxa. The adult and juvenile specimens formed a clade, indicating that the two specimens were of the same species. However, a more comprehensive phylogenetic analysis of all polycotylid specimens is needed before the Wallace Ranch specimens are elevated to their own species.

POS1-55  7:30 pm  Body size evolution in glyptosaurine lizards (Squamata: Anguidae) accurately models paleoclimates for the interior of North America. ElShafie SJ*, University of California, Berkeley; Head JJ, University of Cambridge
Abstract: Poikilothermic vertebrates such as lizards offer viable proxies for terrestrial climate based on the metabolically-scaled relationship between ambient temperature and body size. Ambient temperature constrains maximum body size in extant lizards, but this relationship has not been tested in extinct forms through geologic time. In this study, we estimate mean annual paleotemperature (MAPT) of the North American Interior during the Paleogene from body size in glyptosaurine lizards. We modeled the relationship between skull length and snout-vent length (SVL) for extant anguimorphs and used these models to estimate SVL in glyptosaurines based on fossil cranial material. We then applied the model relationship between mass-specific metabolic rate, maximum SVL and minimum mean annual temperature for extant Heloderma, the largest North American anguimorph, to body size estimates of glyptosaurines to estimate paleotemperatures through time. We find that maximum body size remained approximately constant among the largest glyptosaurines through the Eocene, with estimated MAPT of about 19 – 21°C in the Great Plains and Western Interior during this interval. Our estimates indicate that maximum body sizes of Oligocene glyptosaurines were less than half of those of the largest Eocene glyptosaurines, corresponding to a significant cooling period in the same region. Our results are consistent with other local proxies for the Paleogene of North America, indicating that body size in fossil poikilothermic vertebrates is a useful proxy for estimating terrestrial paleotemperatures over geologic timescales.

POS1-57  7:30 pm  Constraints in crocodylomorph body size evolution. Godoy PL*, University of Birmingham, United Kingdom; Benson RBJ, University of Oxford, United Kingdom; Bronzati M, Bayerische Staatssammlung fur Palaontologie und Geologie, Germany; Butler RJ, University of Birmingham, United Kingdom
Abstract: Evolutionary studies aiming to quantify patterns of morphological radiation in clades that include fossils are mostly temporally limited (i.e. to timescales shorter than 100 Ma), restricted to the origins of modern groups (e.g. birds and mammals), and based on discrete characters. Therefore, more comprehensive analyses are fundamental to understand patterns of phenotypic evolution on long timescales, and not only in successful modern clades, but also in groups that have lower diversity today than in the geological past. We present here a detailed analysis of body size evolution in Crocodylomorpha, a c. 240 Ma-old archosaurian clade that includes modern crocodylians. Body size is strongly related to many aspects of animal physiology and ecology, but has not previously been examined extensively in analyses of phenotypic evolution in crocodylomorphs. Total body lengths for 53 crocodylomorphs were obtained using a formula derived from the regression of body length on dorsal cranial length in modern crocodylians. The estimates were log transformed, so that they represent proportional changes in body size. A time calibrated phylogeny was generated, based on a modified version of a recent crocodylomorph supertree and fossil age data from literature and the Paleobiology Database. Four maximum-likelihood models of trait evolution were fitted using the R package GEIGER: Brownian motion (BM), Ornstein-Uhlenbeck (OU), Early-burst (EB), and trend. The comparison between the AICc weights obtained for each model demonstrates that the OU model provided the best fit. The OU is a process that has a constant pull toward an optimum value, indicating a constrained pattern of body size evolution around a trait ‘optimum’. This suggests constraints within long-term patterns of crocodylomorph body size evolution, consistent with the range of estimated body sizes [most taxa range from 1 to 5 meters] seen in living and fossil taxa, which is narrow compared to that seen in birds and mammals.

POS1-59  7:30 pm  Predicting skull size in Brevirostres using cranial pit depth. Lynch LM*, Oklahoma State University Center for Health Sciences; Lynch ER, Don Sundquist Center of Excellence in Paleontology; Schubert BW, East Tennessee State University
Abstract: Crocodylians are frequently represented in the fossil record by fragmentary cranial elements which are often disregarded in studies. Here we explored the utility of these elements in determining overall skull size. Because most of the cranial bones of crocodylians develop pits on their external surfaces, we sought to determine whether a relationship was present between pit depth and skull dimensions. We measured average pit depth on 13 cranial bones from 13 modern and extinct taxa from which complete specimens are known in Brevirostres. Pit depth, skull length, skull width, and jaw length were all measured using a MicroScribe 3D digitizer. We then ran ordinary least squares regressions between the pit depth of each cranial bone and the skull length, skull width, or jaw length for representatives of Brevirostres and six subclades. Among these 273 regressions, we considered all bones with an r2 value = 0.70 as having a strong predictive power for either skull length, skull width, or jaw length. We found the squamosal, quadratojugal, and maxilla had the strongest relationships to all skull dimensions for nearly every clade but those within Crocodylidae. Caimaninae had the strongest relationship to all skull measurements, with every bone producing an r2 value above 0.80. We suggest using regression equations for bones with r2 values = 0.70 and 95% confidence intervals for the line equation to predict cranial sizes of fragmentary individuals in the fossil record. We applied both of these standards to partial specimens of Alligator found at the 4.5–7 million year old Gray Fossil Site in northeastern Tennessee. The 5 partial specimens were predicted to be similar in size to the adult specimen found at the site and suggests a bias toward preservation of adults. This could indicate the site was dominated by adults, juveniles did not have as high a mortality rate as modern Alligator, or preservation of smaller individuals is not favored at the site.

POS1-61  7:30 pm  The mechanical origin and morphology of the labial (horizontal) shelf in Leptoceratopsia demonstrates it is now a synapomorphy of Neoceratopsia (Dinosauria: Ornithischia). Varriale FJ, King's College; Morschhauser EM*, Drexel University
Abstract: The labial shelf of non-ceratopsid neoceratopsians is a ledge that extends laterally from the basal edge of mandibular teeth, and formed via differential wear as upper and lower dentitions slide incompletely past each other. Previous descriptions of this shelf have referred to it as horizontal, and limited its distribution to members of Leptoceratopsidae. However, the shelf displays a variety of shapes from the recognized horizontal to rostrally or caudally sloping surfaces, as well as a delta configuration. These shapes are a consequence of the number of maxillary teeth that intersect a single dentary tooth during mastication. Given this fuller understanding of the morphology and genesis of the shelf, a re-examination of Neoceratopsia reveals that this character is not limited to leptoceratopsids but present in a number of other neoceratopsians, including the most basal neoceratopsian Liaoceratops, as well as more derived protoceratopsians. Previous phylogenetic analyses recovered the labial shelf as a diagnostic synapomorphy of Leptoceratopsidae. Recent work has not reformulated the character in light of our current understanding of its shape and formation. In order to test the effects of this new understanding on tree topology, the labial shelf was redefined to include the delta configuration and the relevant taxa were recoded. Using several recently published matrices, we found that the labial shelf shifted from being a synapomorphy of Leptoceratopsidae to a synapomorphy for all neoceratopsians. Overall tree topologies remained stable, partly due to characters added to matrices since 2010. The most notable changes include the exclusion of Cerasinops from Leptoceratopsidae, and the recovery of Aquilops as the most basal member of Neoceratopsia in some trees. This new distribution of the “labial shelf” emphasizes the need to more carefully examine the distribution of dental characters and changes in jaw mechanics at the base of Neoceratopsia.

POS1-63  7:30 pm  The visual apparatus of archosaurs: correlates of orbital anatomy, eye size, and behavior. Cerio DG*, Ohio University Department of Biological Sciences; Witmer LM, Ohio University Heritage College of Osteopathic Medicine
Abstract: Like their avian descendants, extinct dinosaurs were visually oriented animals. Reconstructing orbital soft tissues has received little attention and, if not taken into account, the eyeballs of dinosaurs may be mis-sized or positioned inaccurately, leading to poor reconstructions of visual fields and spurious conclusions about behavior and ecology. High-resolution, iodine-enhanced microCT scans were taken of intact heads of a diversity of avian, crocodylian, and squamate specimens. High-resolution microCT scans without contrast enhancement were taken of intact heads of several dozen additional avian specimens. Orbits of key specimens were dissected to identify bony signatures of ocular adnexa and to validate the CT-based analyses. Soft tissues were segmented in Avizo and modeled in Maya. Osteological correlates were identified for orbital soft tissues, including the extraocular muscles, cranial nerves, Harderian gland, lacrimal gland, nasal gland, eyelids, supraorbital membrane, subocular ligament, and nasolacrimal duct. Eyeball size was measured directly and compared with estimates using regressions from the literature. Eyeballs of maximum, average, and minimum size estimates were modeled in Maya for each sample taxon. These eyeball models were subsequently re-inserted along with accessory orbital soft tissues into the digitized skulls. If eyeball models, accessory soft tissues, and/or bones overlapped, the model was rejected as an overestimation. The results indicate that reconstructing accessory soft tissues in the orbits of extant diapsids can provide upper limits on estimates of eyeball diameter and axial length. Thus, optical parameters including focal length and monocular visual field, which depend in part on eyeball size, shape and position, may be modeled based on these constraints. Models of visual fields based on optical parameters will subsequently inform reconstructions of dinosaur visual abilities in a later phase of this project.

POS1-65  7:30 pm  A novel method to estimate cranial muscle strain in fossil and extant vertebrates using digital modelling and visualisation. Lautenschlager S*, School of Earth Sciences, University of Bristol
Abstract: Muscles form an integral part of an animal's anatomy and play a fundamental role in feeding, locomotion and other physiological activities. In particular the anatomy, size and arrangement of the cranial musculature are important factors for an animal’s capability for vocalization, social signalling and food acquisition. In extinct animals, these parameters are often difficult to determine and numerous studies have focussed on the reconstruction of various parts of the musculature in fossils. Inferences on the biology, behaviour and ecology of extinct vertebrates, however, rely considerably on the accuracy of these reconstructions. Although the advent of digital reconstruction techniques has facilitated the creation and testing of musculoskeletal hypotheses in recent years, muscle strain capabilities have rarely been considered. However, muscles can only stretch a certain amount before they tear and, muscular performance is closely related to the extension of muscle fibres. Detailed information on these factors can, therefore, provide a better understanding on the feeding behaviour of extinct organisms. Here, a digital modelling approach using the freely available visualization and animation software Blender is applied to estimate cranial muscle length changes and optimal and maximal possible gape in different vertebrates. Two case studies are presented here using this approach: (i) Investigating different feeding behaviour and dietary specializations of theropod dinosaurs. (ii) Testing of musculoskeletal hypothesis in cynodonts and mammaliaform taxa. Both studies use extant taxa in a phylogenetically bracketed framework and demonstrate that this novel method can be used in a versatile approach to study different anatomical and palaeobiological aspects. Although focussed on the cranial musculature, there is scope for the integration of this method into studies of other musculoskeletal systems.

POS1-67  7:30 pm  The morphology of motion: sub-surface foot trajectories and fossil tracks. Turner ML*, Brown University; Falkingham PL, Liverpool John Moores University; Gatesy SM, Brown University
Abstract: Dinosaur footprints are extremely common in the fossil record. Relative to pedal disparity, the morphological diversity of tracks is inflated by two key factors. First, variation in substrate depth and consistency can cause animals to sink and move differently from step to step. Second, track surfaces can be exposed on bedding planes at any depth within the disturbed volume. To understand these factors, we need to know more about movement below the surface. Even in living animals, however, documenting foot motion within the substrate is difficult because the distal limb is hidden by opaque sediment. We used X-ray Reconstruction of Moving Morphology (XROMM) to visualize and measure sub-surface kinematics in Helmeted Guineafowl (Numida meleagris). In order to image the feet, we walked birds through radiolucent artificial substrates created to mimic dry sand (poppy seeds) and wet, cohesive muds (glass bubbles, clay, water). Undistorted and calibrated biplanar x-ray videos (250 Hz) synchronized with two standard light videos imaged the feet both above and below ground. Our initial efforts have focused on tracing the tip of digit III, a highly identifiable landmark in many dinosaur tracks. Guineafowl display a surprisingly wide range of toe trajectories, even within a single individual. Comparison among and within substrates is hampered by a lack of obvious landmarks. Unlike the discrete stance-swing phases of strides on solid ground, birds on deformable materials appear to transition from air to substrate and back again more gradually. We have identified a number of kinematic events that may be homologous across all substrates that allow paths to be aligned and compared quantitatively. Results suggest that entry and exit motions are decoupled within a single track. Our goal is to use the diversity of guineafowl toe trajectories to provide context for fossil specimens, and to begin to unlock the ancient locomotion preserved within them. (US NSF EAR 1452119 and IOS 0925077)

POS1-69  7:30 pm  One foot, many footprints: the origin of track morphological diversity. Gatesy S.M.*, Brown University; Falkingham P. L., Liverpool John Moores University
Abstract: Fossil tracks offer unrivaled evidence of behavior in long extinct species. Although complementary to skeletal remains, footprints differ in being purely sedimentary structures. Tracks are neither organism nor environment, but emergent features documenting their dynamic, coupled interaction. Track morphologies vary widely. Some disparity is attributable to differences among species, individuals, limbs, and behaviors, but substrate plays a less explored role. We recorded tracks made by Helmeted Guineafowl (Numida meleagris) traversing dry grains (poppy seeds) and a series of wet, cohesive muds (glass bubbles, clay, water). Photogrammetric surface reconstructions record a wide range of morphological variation. Shallow prints can resemble molds of plantar anatomy, but most tracks involve more complex entry and exit patterns arising from foot penetration and sediment collapse. A paleontologist trying to interpret such a spectrum could be easily misled about not only trackmaker identity, but also behavior, ecological interactions, and environment. Such errors can snowball into even more serious miscalculations of taxonomic range, geographic distribution, stratigraphic correlation, and faunal composition. Unlike modern examples, fossil footprints present a critical depth dimension as well. Track surfaces are frequently exposed at bedding planes below the original air-substrate interface. The morphological diversity of Early Jurassic tracks from the Connecticut River valley led workers like Hitchcock in the mid 1800’s to infer the presence of dozens of species of trackmaker. We believe that very few taxa were responsible; most variation can be explained by substrate-induced changes in sub-surface foot motion combined with sampling at different depths. A better understanding of the mechanisms of track formation will help resolve the “one-to-many” conundrum and foster more reliable interpretation of the fossil record. (US NSF EAR 1452119 and IOS 0925077)

POS1-71  7:30 pm  A total-evidence, time-calibrated phylogeny of the ‘waterbird’ assemblage (Tetrapoda, Aves). Moore AJ*, The George Washington University
Abstract: Although the evolutionary relationships of major neoavian groups have remained notoriously difficult to resolve, consensus is emerging across studies in support of a large “waterbird” clade. This diverse assemblage of aquatic and semi-aquatic birds includes most members of the traditional Pelecaniformes (pelicans, frigatebirds, gannets, boobies, darters, cormorants), Ciconiiformes (storks, herons, ibises, shoebill, hammerkop), Procellariformes (tube-nosed seabirds), Sphenisciformes (penguins), and Gaviiformes (loons). However, phylogenetic hypotheses for the group vary substantially across analyses that differ in data type (molecular, morphological) and density of taxon sampling, hindering analyses of trait evolution in this highly diverse group. For the first time, I apply Bayesian phylogenetic methods that incorporate fossils as terminal taxa to a combined matrix of 551 morphological characters and 6,683 basepairs from five genes for 156 taxa (106 extant, 50 fossils). Importantly, I assess the affinities of the Plotopteridae, an extinct lineage of wing-propelled diving birds often interpreted as convergent with penguins, in a matrix that includes a dense sampling of stem and crown penguins. The total evidence Bayesian analysis did not converge after an initial run of 10 million generations and is ongoing. Calibrated morphology analysis weakly supports the divergence of plotopterids from the penguin stem 62.4 Ma (95% HPD = 56.7-69.3 Ma), a topology also supported by parsimony. Uncalibrated Bayesian morphology analysis pulls the plotopterid-penguin clade into a sister group relationship with anhingas and cormorants, reflecting several aspects of cranial and pectoral morphology shared by plotopterids and pelecaniforms and highlighting the potential importance of temporal information in phylogenetics. Recovery of Plotopteridae near the base of Sphenisciformes suggests that early specializations for wing-propelled diving were independently elaborated in each group.

POS1-73  7:30 pm  Dental microwear and macrowear morphology of the Japanese dormice (Mammals: Gliridae Glirulus japonicus). Tomohiko H*, Tokyo Gas Technology Research Institute
Abstract: Japanese dormice (Glirulus japonicus) are endemic to Japan and are thought to be the most primitive species in the Gliridae family. Fossils of this species have been uncovered from the Pleistocene mammal fauna in Japan. However, there is also uncertainty regarding the form of the molars, as there is less morphological information available for comparison with fossils. Using the skull of extant species, with a focus on wear facets and microwear, premolar and molar teeth were studied and compared with other Japanese rodents (Sciurus lis, Microtus montebelli, Myocastor coypus, Rattus norvegicus, and Mus musculus). In addition, wear facets was also identified. Many variations in the microwear patterns were confirmed for Japanese dormice as compared with those for any other rodents. It is possible that chewing patterns and diet are more diverse for this species than for other rodents. This observation is considered to be useful for fossil, function and ecological studies. In the future, there is a need for comparison with Gliridae species in Europe and Asia (fossil and extant).

POS1-75  7:30 pm  Occipital condyle width predicts body mass in proboscideans. Jukar A. M.*, George Mason University
Abstract: Body mass is one of the most important traits of an organism, and has been widely studied in mammalian paleobiology. Many studies have demonstrated significant relationships between dental and skeletal measurements of extant mammals and their body masses. These regression equations have been used to determine the mass of extinct species. A commonly used estimator is the area of the first molar, and this relationship has been found to be robust across many orders of mammals. Proboscideans are the exception. Due to complex replacement patterns and the highly derived structure of extant proboscidean teeth, dental dimensions are not useful in predicting the body mass of extant and extinct species. However, studies have demonstrated the use of shoulder height, limb bone dimensions and volumetric measures in estimating body mass. The problem with the fossil record is that one rarely finds complete skeletons that can be used to estimate shoulder height or volume, and some species are identifiable from cranial remains alone. Therefore, the goal of this study is to determine whether cranial measurements can be used to estimate body mass for proboscideans. Occipital condyle width is a reliable estimator of body mass in sirenians, the sister group to proboscideans, and I hypothesize that it will be a useful estimator of body mass in proboscideans as well. I used two extant species, Elephas maximus and Loxodonta africana to determine whether occipital condyle width correlates with limb bone dimensions which have been shown to predict body mass in both extinct and extant taxa. Preliminary data from two E. maximus and three L. africana show a strong correlation between occipital condyle width and humerus and femur circumference, and humerus and femur length. An analysis of more specimens will be used to verify this trend and generate a predictive equation for limb bone measurements, which will then be used to determine the body mass of extinct species.

POS1-77  7:30 pm  A complete description and phylogenetic analysis of Puijila darwini, (Mammalia: Carnivora) and inferences on the plesiomorphic swimming condition of pinnipeds. Paterson R*, Carleton University; Rybczynski N, Canadian Museum of Nature; Kohno N, National Museum of Nature and Science; Maddin H, Carleton University
Abstract: Whereas the land-to-sea transition is well-documented in many secondarily aquatic mammals, the fossil record of stem pinnipeds is relatively sparse, offering few well-preserved transitional fossils. Due to this paucity of transitional pinniped forms, it remains unclear how the divergent locomotory modes of modern pinnipeds (i.e. forelimb vs hindlimb swimming) and associated morphologies evolved within pinnipeds. In 2009, Rybczynski et al. reported the discovery of Puijila darwini, a putative stem pinniped from the Miocene of Canada’s High Arctic. A brief description was complemented with a preliminary phylogenetic analysis uniting Puijila in a clade with Enaliarctos (previously the oldest known pinniped), Potamotherium (previously considered a stem lutrine) and Amphicticeps. The present study offers a complete description of Puijila, and identifies new potentially taxonomically informative traits shared by Puijila, and other proposed stem pinnipeds. Such traits include reduced, lingually-located M2s and m2s, a posteriorly expanded and shallowly excavated basioccipital, presence of a fossa muscularis anteromedially to the circular infraorbital foramen, confluence of the foramen ovale and caudal alar foramen, and the absence of a postglenoid foramen, among others. To infer the locomotor habits of Puijila, a PCA was performed, following Gingerich (2003), who examined the relationship between osteology and swimming behaviour across a variety of mammalian taxa. PC scores for PC2 (level of aquatic adaptation) and PC3 (preference for forelimb or hindlimb powered propulsion) were calculated for Puijila, plotting it as adapted to aquatic environments (PC2) and as a forelimb-dominated swimmer (PC3). Such results may indicate forelimb powered propulsion evolved before pinnipeds became specialized for marine environments. A phylogenetic analysis will determine if forelimb swimming arose multiple times within pinnipeds.

POS1-79  7:30 pm  Macroevolutionary responses to invasion in terrestrial carnivorans from the early Miocene of North America. Soul L C*, Smithsonian NMNH
Abstract: The macroevolutionary effects of species invasion in vertebrates have been well documented in island settings, but remain relatively unexplored with respect to large-scale continental migrations. Taxonomic diversification rates through time indicate that competitive interactions between endemic and migratory fauna on continents may have been an important factor in shaping community composition. Patterns in ecological diversity, or morphological trait evolution, have the potential to offer more detailed information about these interactions, and the fossil record presents an opportunity to study them on macroevolutionary timescales. Here I focus on whether it is possible to detect long-term patterns in the morphological evolution of terrestrial carnivorans that can be attributed to the influence of invasion. The study period comprises around 10 million years of the early Miocene, from 23.03-13.6 Mya. This represents a comparatively well constrained system, when North America experienced repeated migrations of taxa across the Bering land bridge from Eurasia. I analyse a dataset of continuous and discrete cranio-dental characters for over 50 carnivoran taxa, under a phylogenetic framework. I test three hypotheses; 1) character displacement allows maintenance of a phylogenetically even body size distribution following invasion, 2) phylomorphospace occupation distinguishes successful invaders from other taxa and 3) a geographically constrained phylogenetic model of competition-mediated evolution is the best fit to trait change through time. To ensure validity of results I use a model based simulation approach to test the sensitivity of these methods with respect to trait variance and uncertainty derived from an incomplete and time averaged fossil record.

POS1-81  7:30 pm  A well-preserved malleus in a juvenile specimen of the extinct family Nimravidae. Spearing KD*, Morningside College; Boyd CA, North Dakota Geological Survey; Welsh E, Badlands National Park
Abstract: The auditory ossicles are an amplification system that evolved in terrestrial vertebrates as a way to adapt to hearing out of the water. The number of ossicles is variable among the vertebrate groups, however the presence of three auditory ossicles (malleus, incus, and stapes) is one of the defining characteristics of the Class Mammalia. There is considerable variability in ossicle morphology across the orders of mammals, and in extant and some extinct taxa they can have taxonomic utility. These small bones are only occasionally discovered as fossils, due to their small size, fragility and that they are usually inside the auditory bullae where matrix may be covering them. This project examines the presence of well-preserved auditory ossicles in a specimen of juvenile Nimravus brachyops (F:AM 99259) from the White River chronofauna. In other mammals it is shown that the auditory ossicles are close to adult size and shape at birth, so even though this fossil is a juvenile, the morphology should be very similar to that of adult Nimravids. As the ossicles are preserved in situ and are held in place by matrix, the malleus, as the lateral- most ossicle, is the one that was uncovered most easily. The presence of the incus and stapes cannot be determined at this time. Based upon the morphology of the muscular process, the lateral process, and the head of the malleus, this specimen most closely resembles the malleus of modern felids and canids and is less similar to other members of the modern Carnivora.

Morphological Integration & Modularity (MIM)
POS1-83  7:30 pm  Histological analysis of morphological integration and development in the Weberian apparatus of the zebrafish. Bird NC*, University of Northern Iowa
Abstract: The Weberian apparatus is a complex morphological structure unique to Otophysi, a diverse clade that includes several large teleost orders (Cypriniformes, Characiformes, Siluriformes, and Gymnotiformes). Considered a key innovation for otophysan fishes, the Weberian apparatus produces dramatically increased hearing sensitivity via transforming and amplifying far-field sound (pressure) captured by the swim bladder into a near-field input transmitted to the inner ear via modified vertebral elements. While the skeletal contributions to the apparatus, the Weberian ossicles (claustrum, scaphium, intercalarium, tripus, and os suspensorium), have been described in several species, few studies have focused on their ontogenetic development. Even fewer studies have addressed the development of soft tissue components, or how these elements are integrated within the apparatus. In this study, a detailed histological analysis of the development of the Weberian apparatus in the zebrafish, Danio rerio, is presented, including elements from the vertebrae, ear, swim bladder, ligaments, and other soft tissue components. Preliminary data suggest a strong relationship in developmental timing between the vertebral, auditory, and swim bladder components of the Weberian apparatus, indicating strong functional constraint on development of the apparatus as a unit. The significant morphological and developmental integration are likely required for the Weberian apparatus to become functional quickly during late larval/early juvenile stages.

POS1-85  7:30 pm  A refined system of vertebral column subdivision in Chinook salmon, Oncorhynchus tshawytscha (Actinopterygii: Salmonidae). De Clercq A.*, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand; Perrott M.R., Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand; Davie P.S., Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand; Preece M.A., New Zealand King Salmon, 93 Beatty Street, Nelson 7011, New Zealand; Wybourne B., Skretting Australia, PO Box 117, Rosny Park, TAS 7018, Australia; Ruff N., Skretting Australia, PO Box 117, Rosny Park, TAS 7018, Australia; Huysseune A., Evolutionary Developmental Biology, Ghent University, Ghent, Belgium; Witten P.E., Evolutionary Developmental Biology, Ghent University, Ghent, Belgium
Abstract: Teleost vertebral bodies are often similar in size and shape, but neural arches, haemal arches and ribs show regional differences. Here it is asked if the presence and characters of vertebral body appendages can be used to refine the system of vertebral column subdivision in juvenile Chinook salmon. Animals raised at 8 and 12°C were studied at 1400 and 1530 days post hatching. Anatomy and the skeletal tissue composition of the vertebral column were studied using Alizarin red S whole mount staining and histological serial sections. Based on the presence of neural arches, parapophyses, ribs, haemal arches and caudal fin endoskeletal elements, six regional types of vertebrae are recognised: (1) postcranial, (2) abdominal, (3) transitional, (4) caudal, (5) preural and (6) ural. Postcranial vertebrae (1) carry vestigial parapophyses and lack ribs. In abdominal vertebrae (2) ribs articulate with parapophyses fused to basiventrals. Elastic- and fibrohyaline cartilaginous joints and Sharpey’s fibres connect the bone of the parapophyses and ribs. Neural arches of postcrancial and abdominal vertebrae are fused to the basidorsals. In the transitional region (3) the parapophyses gradually transform into haemal arches. The neural and haemal arches fuse to the vertebral bodies. Ribs decrease in size, anterior to posterior. Vestigial ribs remain attached to the haemal arches with Sharpey’s fibres. In caudal vertebrae (4) basidorsals and basiventrals are small and internalized into the bone of the vertebral centrum. Preural vertebrae (5) carry neural and haemal arches that also support the caudal fin. Two ural vertebrae (6) carry hypurals and epurals that represent modified haemal and neural arches respectively. The postcranial and transitional vertebrae and their respective characters are usually not recognised but should be considered for subdividing the vertebral column into distinctive regions.

POS1-87  7:30 pm  Chemical manipulation of axolotl regeneration and angiogenesis. Dickie R*, Towson University; Wilkins D, Towson University; Ritenour A, Towson University
Abstract: In mammals, tissue repair requires angiogenesis, and angiogenesis requires the VEGF, Notch, and TGF-B signaling systems. The dependence of epimorphic regeneration on the formation of new blood vessels and these signaling pathways is less well known. We used small molecule inhibitors and/or activators of these signaling pathways and assessed their effect on tail regeneration and regenerative angiogenesis in the axolotl tail following amputation. Larval and juvenile salamanders were treated daily with drug or vehicle control. Each animal’s regenerative outgrowth and vascular density was quantified using ImageJ over the period of regeneration. Vascular density and regenerative outgrowth were not strongly correlated: a decrease in vascular density did not predict poor regenerative ability, and poor regenerative ability was not necessarily coupled to low vessel density. The results are consistent with there being fundamental differences in mammalian tissue repair versus ectotherm regeneration. This work provides a first step towards developing a system for the manipulation of regeneration.

POS1-89  7:30 pm  Ontogenetic integration and modularity in the dermatocranium of the Greater Short-horned lizard, Phrynosoma hernandesi. Powell G.L. *, University of Calagary; Russell A.P. , University of Calgary; Jamniczky H.A., University of Calgary; Hallgrímsson B., University of Calgary
Abstract: Ontogenetic change in dermatocranial form in a series of 79 Phrynosoma hernandesi (54 F: 25 M) was examined, using geometric morphometric analytical techniques. Multivariate regression of Procrustes residuals on ln(centroid size) indicated that allometry accounts for ~53% of the total sample variance in landmark configuration, and suggests no sexual shape dimorphism. Groupings of multivariate regression coefficients by magnitude and sign suggest regions of localized allometric integration of the dermatocranium, principally the posterior regions of the parietal, the squamosals, and the posterior region of the frontal, all of which bear horns throughout the genus. A principal component analysis of the variance-covariance matrix generated from the residuals of the multivariate regression yielded a first principal component which describes shape variance concentrated in the posterolateral and posterior regions of the dermatocranium. Hypotheses of modularity for the dermatocranium based upon observations of geographic variation in external head shape, and groupings of the PC1 coefficients by magnitude and sign, were tested with multi-set RV coefficients. We failed to reject an hypothesis based upon PC1 groupings, dividing the dermatocranium among six modules. Three of these encompass the dermatocranial horn suite of P. hernandesi. We hypothesize that adult dermatocranial shape in P. hernandesi results from the interaction of this modularity and localized allometric integration. Dermatocranial shape and horn morphology display great disparity among the species of Phrynosoma, and our findings for P. hernandesi suggest that evolvability in the dermatocranium may result from greater independence in variation and response to selection among its parts.

Evo-Devo (EVD)
POS1-91  7:30 pm  Comparative study of hexose transporters in ostrich small intestine. Hussar P*, University of Tartu; Kärner M, University of Tartu; Järveots T, Estonian University of Life Sciences; Duritis I, Latvian University of Agriculture
Abstract: Background and aim of the study. As there are notes in literature about high mortality of ostrich chicken in farms especially until 30 days after hatching (mortality rate about 46 %) and there are relatively few data about scientific research on organ systems, including the gastrointestinal system, at early periods of ontogenesis of ostrich chicken, more detailed scientific research is necessary to carry out in this field. As carbohydrates are the main energy source of food, but up to now there is few information about the localization of hexose transporters in ostriches gastrointestinal tract the aim of the present study was to localize glucose transporters-2 and -5 in ostriches small intestine in their first postnatal month. Methods. Material from duodenum and terminal zone of ileum was collected from eight female ostriches (Struthio camelus var. domesticus): three chicken after hatching, three 7 and three 30 days old ostriches. Material was fixed with 10% formalin, embedded into paraffin, slices 7 um thick were cut followed by immunohistochemical staining with polyclonal primary antibodies Rabbit anti-GLUT-2 and Rabbit anti-GLUT-5 carried out according to the manufacturer's guidelines (IHC kit, Abcam, UK). Results and conclusion. The results showed that the staining for both antibodies was weaker of ostriches after hatching compared to 7 and 30 days old ostriches showing that the small intestine of ostriches immediately after hatching is not entirely able for transportation of carbohydrates. The results of our study may indicate to the possibility of close relationship between feeding and ability to transport sugars in gastrointestinal tract.

POS1-93  7:30 pm  Fetal membrane morphology in oviparous lampropeltine snakes (Colubridae). Kim YK*, Trinity College; Blackburn DG, Trinity College
Abstract: In oviparous reptiles, fetal membranes line the eggshell and maintain the developing embryo by regulating gas exchange and the uptake of water and calcium. Unfortunately, the scarcity of morphological studies hinders an understanding of their functional specializations and evolution. We have used scanning electron microscopy to study fetal membrane morphology in two oviparous snakes, the Pueblan milksnake, Lampropeltis triangulum campbelli, and the kingsnake, Lampropeltis getula. In both species, two major fetal membranes, the chorioallantois and yolk sac omphalopleure, are present. The chorioallantois in early development is characterized by enlarged chorionic and allantoic epithelia and avascular connective tissue. As the chorioallantois matures, vascularization increases and the chorionic epithelium thins to facilitate gas exchange. The yolk sac omphalopleure is initially an avascular structure which is transformed into an omphalallantois upon vascularization by the allantoic capillaries. As the isolated yolk mass regresses and the epithelia thin, the omphalallantois is transformed into a chorioallantois, enhancing the growing embryo’s potential for gas exchange. In early development, the chorionic epithelium exhibits microvilli that increase surface area for water uptake. The allantoic epithelial cells may produce allantois fluid involved in water uptake and storage. Our findings are consistent with a previous study on the corn snake, Pantherophis guttatus, but offer novel morphological observations and functional hypothesis. Comparisons of fetal membranes to those of other squamate species may contribute to a reconstruction of ancestral characteristics for snakes.

POS1-95  7:30 pm  Placental morphology in viviparous North American water snakes (Colubridae). Blackburn D. G.*, Trinity College; Johnson A.R., Trinity College; Anderson K.E., Cornell University; Marquez E.C., Boston University; Callard I.P., Boston University
Abstract: In viviparous snakes and lizards, placentas maintain developing embryos in the maternal uterus through transfer of respiratory gases, water, and nutrients. As part of a long-term survey of reptile placentation, we used light microscopy, SEM, and TEM to study placental membranes in the water snake Nerodia sipedon (Colubridae). The chorioallantois and adjacent uterine lining are highly vascularized with thin epithelia, features that enhance gas exchange. The yolk sac placenta shows evidence of histotrophic nutrient transfer. Scanning EM reveals elaborate networks of capillaries in fetal and maternal components of both placentas. The chorioallantoic placenta replaces the yolk sac placenta during development to meet growing embryonic needs for gas exchange. In late development, earlier functions of the fetal yolk sac placenta are evident in residual yolk droplets and absorptive cells. Placentation in Nerodia is similar to that of other thamnophiine snakes and has converged evolutionarily on viviparous lizards and eutherian mammals.

POS1-97  7:30 pm  A novel pattern of yolk mobilization in developing squamate reptiles. Powers K.G.*, Trinity College; Blackburn D.G., Trinity College
Abstract: Corn snakes (Pantherophis guttatus) serve as a valuable model for developmental studies. Unlike birds, which employ a well-vascularized yolk sac to transport nutrients to the embryo, corn snakes use an elaborate network of blood vessels that penetrate into the yolk mass itself. In this study, we have used light microscopy and SEM to image yolk samples from eggs of mid to late developmental stages. Our observations have revealed how the large yolk mass is vascularized, cellularized, and mobilized for embryonic use. As the endodermal cells proliferate, they form elongated cords of interconnected cells that are filled with yolk platelets. During angiogenesis, the vitelline blood vessels become encased in these cells, allowing them to transport the products of yolk digestion back to the developing embryo. Our lab has found that this unusual mechanism of yolk cellularization and mobilization occurs in other snakes as well as lizards and may be ancestral for squamate reptiles. Studies of this developmental mechanism offer information on patterns from which viviparity has evolved and contribute to an understanding of reptilian evolutionary history.

POS1-99  7:30 pm  Endocrine control of limb development in the direct-developing frog Eleutherodactylus coqui (Anura: Eleutherodactylidae). Laslo M*, Harvard University, Museum of Comparative Zoology; Hanken J, Harvard University, Museum of Comparative Zoology
Abstract: Direct development has evolved independently in at least a dozen anuran lineages. Direct-developing frogs, including the Puerto Rican coquí, Eleutherodactylus coqui, hatch from terrestrial eggs as miniature adults. Their embryonic development is characterized by precocious formation of adult morphology, including limbs. In metamorphosing frogs, formation of limbs at metamorphosis is mediated by thyroid hormone (TH). Changes in temporal or spatial expression of the nuclear thyroid receptor - (TR) or thyroid receptor - (TR) in the limb could facilitate their early development in E. coqui. qRT-PCR analysis shows that TR and TR are indeed expressed at every stage of limb development. Moreover, these TRs may be functional... T3 treatment, for example, appears to alter expression of some candidate T3-response genes in the brain. These data suggest that the E. coqui limb is competent to respond to TH and that TH-mediated development may begin very early in embryonic development. However, the TR dual-function model suggests that both T3-bound and unbound TRs play important developmental roles. Thus, quantification of native THs in the developing embryo is needed to more precisely determine T3 availability and the role of the receptor. Liquid-chromatography mass-spectrometry (LC-MS) is an accurate and sensitive method to measure THs. LC-MS detects both T4 and T3 at the initial stage of limb development in E. coqui embryos (TS5), well before embryonic TH synthesis begins at TS9. Thus, maternally derived TH likely plays an important role in precocious limb formation. This work is an important first step in describing the physiological mechanisms that underlie direct development and will serve as a comparison to examine the evolution of this life history strategy in other amphibian groups.

POS1-101  7:30 pm  A survey of morphological and heterochronical variations during early ontogeny in six families of Leptodactyliformes (Anura: Hyloides). Grosso J.R.*, UEL-CONICET; Vera Candioti M.F., UEL-CONICET; Barraso D., IDEAus-CONICET; Nogueira Costa P., Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro; Barrionuevo S., División Herpetología. Museo Argentino de Ciencias Naturales – CONICET; Natale G., CIMA-CONICET; Baldo J.D., IBS, CONICET-UNaM
Abstract: The early ontogeny in anurans includes the occurrence of transient, exclusively embryonic structures, plus the initial stages of development of larval features. We compared developmental series of 13 species belonging to six families of the clade Leptodactyliformes, in order to record morphological and heterochronical changes among them. Tailbud embryos of Telmatobius oxycephalus (Telmatobiidae), Limnomedusa macroglossa (Alsodidae), and ceratophryid Ceratophrys cranwelli, C. ornata, and Chacophrys pierotti are well-pigmented and have no dorsal curvature. Conversely, Batrachyla leptopus (Batrachylidae) and six species of Odontophrynidae have pigmented but kyphotic embryos. Embryos of Cycloramphus brasiliensis (Cycloramphidae) lack pigmentation completely. Three different adhesive gland types occur: type A in Ceratophryidae and L. macroglossa, type C in Odontophrynidae and B. leptopus, and type B in T. oxycephalus, this latter being typical of unrelated bufonids. The adhesive glands are absent in C. brasiliensis. Regarding gills, two pairs occur in Odontophrynidae, L. macroglossa, and C. brasiliensis¸ and a third pair develops in Ceratophryidae, T. Oxycephalus, and B. leptopus, in this latter case poorly developed. Ontogeny of the oral disc is similar in all species with labial tooth row formula 2/3, whereas Ceratophrys spp. differ in development of supernumerary tooth rows. Some patterns will likely be proven diagnostic of some clades (e.g., type B adhesive glands in Telmatobius, three gill pairs in ceratophryids). On the other hand, the unusual set of features of the exotrophic, semiterrestrial C. brasiliensis specimens (large yolk provision, and lack of pigmentation and of adhesive glands) are typical of endotrophic embryos, and possibly conserved within the genus.

POS1-103  7:30 pm  Evolutionary and developmental mechanisms underlying craniofacial variation in Neotropical bats. Camacho J*, Harvard University; Heyde A, Harvard University; Abzhanov A, Imperial College London
Abstract: Parallelism between individual development and the pattern of organismal evolution has been discussed for almost 200 years, but examples of the connection between these fundamental biological phenomena have been isolated and phylogenetically disparate. The New World leaf-nosed bats (Phyllostomidae), arguably the most ecologically diverse clade of mammals, have evolved extraordinarily diverse faces and skulls adapted for many different food types, such as insects, fruit, nectar, other vertebrates, and blood. To understand the processes that generated this diversity, we employ a phylogenetically informed geometric morphometric approach analyzing the variability of 3D skull landmarks from developmental and adult data across several lineages. Our results demonstrate widespread peramorphosis in phyllostomid skull morphologies and reveal that their distinctive ecomorphologies are largely achieved through “terminal addition” as the evolutionarily more recent features in cranial morphology emerge later in bat development. Phyllostomids, thus, provide a real-world example of “ontogeny recapitulates phylogeny” with important implications for understanding the evolution of adaptive morphological diversity in vertebrate body form.

POS1-105  7:30 pm  Hoxa11 and Hoxd11 loss-of-function mutations alter pisiform growth plate organization. Kjosness KM*, The Pennsylvania State University; Hines JE, The Pennsylvania State University; Reno PL, The Pennsylvania State University
Abstract: Mammalian pisiforms are typically elongated and develop from two centers of ossification with a single organized growth plate on the palmar end; however human pisiforms are unique among mammals because they are short, develop from a single ossification center, and lack a growth plate. Hox genes provide crucial developmental patterning information, and are thought to influence growth plate formation. Hoxa11 and Hoxd11 are expressed around the developing pisiform in mice, and mutations to these genes result in abnormal shortening of the pisiform. This study seeks to determine if Hoxa11 and Hoxd11 loss-of-function mutations influence pisiform growth plate formation and chondrocyte organization, resulting in the observed pisiform shortening compared to wild type. Histological analyses of Hoxa11 and Hoxd11 mutant mouse pisiforms indicate that abnormal chondrocyte organization occurs in heterozygotes and homozygotes for either deletion. Severity of organizational abnormalities is dosage dependent for both genes. Hoxa11 mutants lack a distinct hypertrophic zone and exhibit a reduced columnar zone. All chondrocytic zones appear reduced in Hoxd11 heterozygotes, with more marked disorganization in homozygotes. Hoxd11 mutants also have irregular progression of the ossification front. These results support the role of Hox genes in pisiform growth plate formation and overall pisiform length in Hoxa11 and Hoxd11 mutant mice. Understanding the influence of Hox genes on chondrocyte organization may also help to explain developmental processes responsible for growth plate loss in the unique human pisiform. This research is funded by the Hill Fellowship (Department of Anthropology, Penn State) and NSF BCS-1540418.

POS1-107  7:30 pm  Evolution of fetal skeletogenesis in mammals: patterns, diversity, and modularity. Koyabu D*, University Museum, University of Tokyo; Sánchez-Villagra M, Palaeontological Institute and Museum, University of Zürich
Abstract: The multiple skeletal components of the body originate asynchronously, and their developmental schedule varies across mammals. It has been assumed that simple alterations in the onset, duration, and tempo of development are regarded as causes of profound morphological changes. Until recently, however, most heterochronic studies on mammals have focused on postnatal life, and our knowledge of fetal development has largely been restricted to model organisms. The critical stages for examination of skeletogenesis are fetal or around the time of birth, and thus non-model organisms are rarely available and difficult to sample. Gathering more than thousand fetal and neonatal specimens from museum collections and adopting nondestructive microtomographic imaging technique, we described the sequence of skeletogenesis of more than 100 mammalian species. Mapping this comprehensive dataset to the reported molecular phylogeny enabled us to reconstruct the ossification sequence for the common ancestor of Mammalia and to identify evolutionary shifts of ossification sequence at all nodes. Timing of limb development appears to be strongly related to the modes of newborn lifestyle, most clearly exemplified in bats. Compared to other amniotes, timing of the neurocranium development was considerably accelerated during the origin of mammals. Furthermore, association between developmental timing of the supraoccipital and relative brain size was confirmed among mammals. We also highlight that skull bones form two separate modules, one consisting explicitly of dermal bones and the other of endochondral bones. However, neither mesoderm vs. neural crest origin nor phenotypic modularity identified based on adult metric traits appear to be related to cranial ossification heterochrony. We suggest that the mode of ossification (dermal or endochondral) imposes evolutionary bias on cranial heterochrony.

POS1-109  7:30 pm  Linking morphometrics with 3D analysis of gene expression patterns of early limb development in an Apert syndrome mouse model. Sastre J, Centre for Genomic Regulation; Mateu R, Universitat de Barcelona; Russo L, Centre for Genomic Regulation; Richtsmeier J, Pennsylvania State University; Sharpe J, Centre for Genomic Regulation; Martínez-Abadías N*, Centre for Genomic Regulation
Abstract: Understanding how gene networks coordinate organogenesis remains one of the key questions of developmental biology. An important step has been the development of new techniques to visualize gene expression patterns within developing structures in a three-dimensional (3D) framework, such as Optical projection tomography (OPT). However, there have been few attempts to quantitatively analyze the shapes of gene expression domains. Here we combined OPT with Geometric Morphometrics (GM) for embryonic phenotyping of the developing limbs of the Fgfr2+/P253R Apert syndrome mouse, a model for a congenital disorder characterized by cranial, neural, and limb malformations such as syndactyly. We explored early limb morphogenesis to assess whether the P253R mutation in the Fgfr2 gene induces changes in the expression pattern of Dusp6, a downstream target of the FGF/FGFR signaling pathway, and whether these genetic changes can be associated with limb malformations in mutant mice. GM analyses of 3D landmark-based data recorded on OPT images of 11.5 embryonic day (E11.5) embryos labeled for Dusp6 expression using whole-mount in situ hybridization revealed differences in limb size and shape between mutant and unaffected littermates. At E11.5, the limbs of mutant mice were significantly smaller; and the shapes of the limbs and of the 3D expression pattern of Dusp6 were also affected, especially of hind limbs. This suggests that altered FGF/FGFR signaling has direct consequences on target genes that contribute to limb malformations as early as E11.5. Precise embryonic phenotyping of Apert syndrome mice with more time points and genes is ongoing and will help us identify the origins of abnormal limb morphogenesis. By combining OPT and GM, our method is a potentially useful tool to compare normal and disease-altered patterns of variation and to reveal how the genotype translates into the phenotype. Grant support: FP7-PEOPLE-2012-IIF 327382, SEV-2012-0208.

POS1-111  7:30 pm  Expression of a set of cranial neural crest regulatory genes in the dental mesenchyme during mouse tooth development. Woodruff E.D.*, University of Florida; Mangino A.A., University of Florida; Bloch J.I., Florida Museum of Natural History; Cohn M.J., University of Florida   Department of Biology
Abstract: During mammalian embryonic development, cranial neural crest cells are specified in the dorsal neural tube by a set of regulatory genes that distinguish these cells from adjacent non-migratory cells of the neural tube and the non-neural ectoderm. Cells derived from the cranial neural crest contribute to the mesenchymal tissue in the branchial arches that form the head, including the dental mesenchyme in developing teeth. Tooth development has been studied extensively in mice (Mus musculus) and the expression patterns of many genes necessary for proper tooth development are well documented. However, similarities in the genetic regulation of cranial neural crest development and tooth development have not been explored in depth, despite the fact that cranial neural crest-derived cells comprise much of the dental mesenchymal tissue in developing teeth. This study documents the spatial expression patterns of a set cranial neural crest regulatory genes in developing mouse teeth to test the hypothesis that a gene regulatory network that is initiated in embryonic development in the cranial neural crest is later re-activated during dental development. In situ mRNA localization analyses were used to examine spatial expression patterns of these genes at three key stages in dental development: bud (E12.5), cap (E14.5), and bell (E16.5-17.5) stages. Preliminary results suggest that at least some of these genes are expressed in both the cranial neural crest cells and the dental mesenchyme. Additional in situ assays to detect expression of other genes associated with the cranial neural crest will demonstrate whether the expression of this entire set of regulatory genes is held in common between cranial neural crest cells and their derivatives in the dental mesenchyme, or alternatively, if only part of this gene network is re-activated during tooth development.

POS1-113  7:30 pm  Fetal growth in mysticete and odontocete skulls: the developmental origins of the highly divergent skulls of cetaceans . Roston RA*, Duke University; Yamato M, National Museum of Natural History; Roth VL, Duke University
Abstract: Cetaceans (whales, dolphins, porpoises) have highly divergent skulls, but how the mammalian skull groundplan became modified for aquatic life and how that morphology arises in ontogeny is still not well understood. The arrangement of the skull differs significantly in the two sub-clades of crown cetaceans: toothed whales (odontocetes) and baleen whales (mysticetes). Miller (1923) coined the term “telescoping” to describe a major aspect of cetacean skull morphology, wherein the cetacean skull bones overlap to a much greater extent than is the case in overlapping or squamous sutures observed in other mammals; these changes occurred concomitant with the nares moving posterodorsad to form a blowhole. In order to elucidate the developmental mechanisms that generate telescoped skull morphology, we documented and compared the ontogeny of cetacean skulls using measurements from CT scans of ontogenetic series of cetacean fetuses representing the two crown cetacean sub-clades. Preliminary findings suggest, in contrast to previous reports, that change in skull length relative to total body length is indistinguishable from isometry during the early portion of the fetal period. Additionally, Balaenoptera physalus (mysticete) and Stenella attenuata (odontocete) differ in positive allometry of several skull features relative to skull length during fetal growth, which contribute to the development of the two adult telescoped conditions. This study on the ontogeny of the extremely divergent morphologies of cetacean skulls allows us to examine how changes in development shape the limits of morphological variation.

POS1-115  7:30 pm  Testing a model of scute patterning in cheloniid sea turtles. Moustakas-Verho JE, Institute of Biotechnology, University of Helsinki; Wyneken J*, Florida Atlantic University
Abstract: A recent model suggested that placodal signaling centers in primordial carapace are likely to act as developmental modules that are responsible for the evolution of scutes in turtles. Further, the regulation of these centers has allowed for the diversification of turtle shell’s scute patterns. Scute anomalies occur during embryogenesis and may be connected with environmental conditions during incubation. Environmental factors have been hypothesized to contribute to the development of scute anomalies; some factors may be related, such as mechanical stresses that occur with desiccation. Here we quantify and compare scute pattern anomalies in cheloniid sea turtles that were incubated under natural conditions, but during normal and hotter-than-normal years. Three types of scute anomalies were found: supernumerary scutes, atypically shaped scutes, and absence of some regular scutes. As has been noted in other turtle species, these types of anomalies may occur separately or together in the same individual. By comparing the scutes of hatchlings sampled from in situ nests, we test the hypothesis that abnormal growth or a shift in reaction-diffusion dynamics may be a consequence of the combined thermal and hydric environments. When scute asymmetries occur under extreme thermal conditions, the relative distances of the forming scute primordia resulting in “vacant” areas where supernumerary primordia could have a thermal basis.

POS1-117  7:30 pm  Functional characterization of enhancer variants driving human evolution. Ryu AH*, UCSF; Pollen A, UCSF; Kircher M, University of Washington; Martin B, University of Washington; Shendure J, University of Washington; Pollard K, UCSF; Ahituv N, UCSF
Abstract: The genetic changes underlying the myriad differences between humans and other primates are largely unknown, although it is clear that gene regulatory changes play an important role. Whole-genome comparisons show that protein-coding sequences do not vary greatly between humans and other primates. Rather, the vast majority of inter-species genetic differences lie in non-coding regions of the genome, namely enhancers. Enhancers are regulatory sequences that determine when, where, and how much a protein-coding gene is expressed in every animal tissue. Even though enhancers tend to be evolutionarily conserved, they evolve faster than coding regions, suggesting that changes in regulatory DNA play an important role in evolution. Many authors, starting with the seminal work of King and Wilson, have suggested that the majority of the changes that distinguish humans from other hominoids are to be found in the 98.5% of the genome that is non-coding. As our knowledge of the regulatory code progresses, the closer we are to understanding the molecular basis for human evolution, development, and disease. To identify human-specific regulatory elements, several groups have developed computational approaches to scan mammalian genomes for evolutionarily conserved sequences that have changed significantly and uniquely in humans. The Pollard group has previously identified 721 human accelerated regions (HARs) using a method based on likelihood ratio tests for accelerated sequence divergence on the human lineage. 92% of these HARs are non-coding, further underscoring the likely importance of regulatory sequences in recent human evolution. Although a subset of HARs has been shown to act as enhancers in vivo, the vast majority of the HARs remain to be functionally characterized. Here, I present my work on functionally characterizing these HARs en masse, and identify human-specific nucleotide variants driving divergence in human and chimpanzee gene regulation during development.

Hard-tissue Biology (HRD)
POS1-119  7:30 pm  Evidence of hyperostosis in the oarfish (Actinopterygii: Regalecus russellii). Paig-Tran EWM, CSU Fullerton; Barrios Andrew*, CSU Fullerton; Ferry Lara, Arizona State University West
Abstract: Hyperostosis, extra bone growth, has evolved independently in at least 22 families of fishes most of which are tropical or subtropical marine species. While the presence of hyperostosis is well documented in fishes, the mechanism driving the development of the extra bone growth is unclear. We documented regular, repeating hyperostosis along the dorsal pterygiophores in mature Oarfish, Regalecus russelii; e.g. those with total lengths greater than 3m. In oarfish, the majority of the skeleton contains low mineralized, acellular bones with localized areas of stiffened, cellular bony growths near the distal edge of the pterygiophores. We propose these additional skeletal elements help to provide a stiffened lever structure for dorsal fin undulation. Oarfish lack a swim bladder so they must continuously beat their bi-directional dorsal fin to maintain position within the water column and while engaged in locomotory behavior. It is therefore not surprising that these fishes have areas of localized, hyperostotic skeletal elements that are capable of withstanding higher mechanical pressures and that undergo bone remodeling.

POS1-121  7:30 pm  Bone growth and bone morphology in Atlantic salmon under conditions of severe phosphorus deficiency: The uncoupling of bone formation and bone mineralisation. Witten PE*, Ghent University, Department of Biology; Owen MAG, Skretting Aquaculture Research Centre; Fontanilllas R, Skretting Aquaculture Research Centre; Soenens M, Ghent University, Department of Biology; McGurk C, Skretting Aquaculture Research Centre; Obach A, Skretting Aquaculture Research Centre
Abstract: Teleosts, can obtain calcium (Ca) from the water to mineralise their bones. Contrary to tetrapods teleosts do not suffer from dietary calcium deficiency, but depend on dietary phosphorus (P) intake to mineralise the bones. To understand the effect of low dietary P intake on the morphology of the vertebral column a P deficiency was induced in post-smolts (early seawater phase) of Atlantic salmon Salmo salar. The P content of the diet was reduced by 50% for 10 weeks. The vertebral column morphology was subsequently evaluated using X-rays, histology and histochemical (detection of minerals) analyses. Bones and scales were chemically analysed for the Ca and P content. In animals that received a P deficient diet the bone and scale mineral content decreased by c. 50%. The X-rays of the deficient animals exhibited undersized vertebral bodies and enlarged intervertebral spaces. Contrary to the X-ray-based diagnosis, histology revealed that vertebral bodies had a regular size and regular internal bone structures (trabeculae); the intervertebral spaces were not enlarged. Bone matrix formation continued uninterrupted, albeit without traces of minerals in the bone matrix. Likewise scale growth continued with newly formed non-mineralised annuli that retain the regular spacing. The experiment generated a homogeneous osteomalacia of vertebral bodies but no skeletal malformations and demonstrates (a) the dependency of Atlantic salmon on dietary P and (b) bone formation and bone mineralization are, to a large degree, independent. The finding that a severe deficit in mineralization did not alter the structure or growth of vertebral bodies was unexpected and is counter to the accepted paradigm in both teleosts and tetrapods. The fact that large individuals of other osteichthyan groups such as Sturgeons, Lungfish and Coelacanths maintain a non-mineralised vertebral column raises fundamental questions about the primary function of vertebral body mineralization.

POS1-123  7:30 pm  Ligaments that push and cartilage that bends: Diverse connective tissue morphology in teleost fishes is associated with diverse functions. Staab KL*, McDaniel College
Abstract: Teleost fishes provide a classic example of cranial kinesis, where bones of the head move relative to each other especially during feeding. Functional morphological studies on fish feeding have focused on bone movement and the muscles behind it, but the links among bones are an important component. While mammals possess distinct connective tissue (CT) morphologies (e.g., ligaments made of dense regular CT with few cells and parallel fibers), teleosts exhibit diverse morphologies of CTs linking the bones, to which less attention has been paid in a functional context. Two case studies here show that the CTs linking teleostean cranial bones are of equal importance to the functional unit. For example, cypriniform fishes (carps, zebrafish) have a network of ligaments involved with jaw protrusion. The ligament connecting the premaxilla to the kinethmoid (and ultimately the rest of the head) is highly cellular and not fibrous. Functional experiments have shown that the kinethmoid begins rotating prior to jaw protrusion, evidence that the kinethmoid – and its ligament – are pushing the jaw forward. Some teleostean CTs are assumed to be composed of hyaline cartilage because they stain with Alcian blue in whole mount preparations, but often these tissues do not have the same cellular morphology and/or function as mammalian cartilage. In poeciliid fishes (mollies, guppies), a rod of cartilage (Meckel’s) linking the dentary to the anguloarticular undergoes >90 degrees of bending during feeding. Histology reveals that the articulation points of the Meckel’s cartilage resemble mammalian hyaline cartilage with cells trapped in a hyaline-like matrix; however, in the middle of the rod of cartilage, presumably where jaw bending occurs, the tissue is more cellular and has much less extracellular matrix. This work demonstrates that the cellular morphology of biomechanical linkages in fishes deserves closer attention, especially when studying the overall function of a cranial unit.

POS1-125  7:30 pm  High-resolution study of salamander braincase morphology using micro-CT reveals novel phylogenetic information. Szostakiwskyj M*, University of Calgary; Anderson JS, University of Calgary
Abstract: The prevalence of neotenic taxa, animals that retain juvenile features as adults, has introduced numerous complications to morphological phylogenetic analyses of salamanders. One potential solution is the study of the braincase: in salamanders it undergoes most of its development pre-metamorphosis, but variation amongst families has yet to be documented. We scanned 28 species of salamander, including metamorphic and neotenic representatives of all 10 families, using micro-CT to visualize changes in braincase morphology across the group. We present variation in a number of braincase features that were previously thought to be generalized across salamanders, including: the bony boundaries of the brain and nerves, the afferent vascularization, and the morphology of the sensory capsules. Furthermore, features that were considered paedomorphic, and therefore phylogenetically uninformative, such as vomerine dentition, are here shown to differ amongst adults of different families. The inclusion of this novel variation may help to elucidate the morphology-based phylogenetic relationships of salamanders and may help to resolve many of the outstanding questions of salamander evolution and radiation.

POS1-127  7:30 pm  The overlooked cranial sesamoids of squamate reptiles. Montero R.*, Universidad Nacional de Tucumán. Argentina; Daza J. D., Sam Houston State University; Bauer A. M., Villanova University; Abdala V., Universidad Nacional de Tucumán, Argentina
Abstract: Sesamoid bones are elements embedded within a tendon or a muscle. Although these bones have been reported frequently in the postcranium of vertebrates, cranial sesamoids have been reported almost exclusively in fishes. The only tetrapod cranial sesamoid reported until now has been the transiliens cartilage of crocodiles and turtles, located in the bodenaponeurosis of the adductor muscles of the jaw. Here we report the presence of cranial sesamoids in two different positions in the skull of several squamate species. One sesamoid is attached to the cephalic condyle of the quadrate of Ophiodes intermedius (Anguidae), which is embedded in the bodenaponeurosis and the jaw adductor muscles. This sesamoid seems to have a function related to the protection and movement of the adductor tendons, and might play a role in streptostyly of the quadrate. The other sesamoid is consistently found at the base of the cranium, capping the sphenoccipital tubercle (basal tubera), on the lateral side of the basioccipital – basisphenoid suture. This bone has previously been reported as “element-X” in amphisbaenians, and we here reinterpret it as a sesamoid, as it is associated with tendons of the cranio-cervical muscles (m. longus colli). This bone is also embedded in cartilage, at least earlier during the development, and seems to have the function of resisting tension-compression forces generated by the muscle during flexion the head. We have confirmed the presence of similar structures in three families Calyptommatus leiolepis (Gymnophthalmidae), Chondrodactylus bibronii, Chondrodactylus angulifer (Gekkonidae), and Paradelma orientalis(Pygopodidae). This new interpretation changes our understanding of the head skeleton in squamates, and suggests that these elements might be more widespread, at least in squamate reptiles.

POS1-129  7:30 pm  Integration of histology and morphology to assess the skeletal maturity of early-diverging dinosauromorphs. Bano L.S.*, Virginia Polytechnic Institute and State University; Griffin C.T., Virginia Polytechnic Institute and State University    
Abstract: The Upper Triassic sediments of North America record the evolution of many extant vertebrate groups, including Dinosauromorpha; however, growth patterns of early dinosauromorphs are relatively unexplored because of a lack of well-preserved growth series. Additionally, our knowledge of the relationship between histological and external morphological ontogenetic changes in this clade is lacking. Dromomeron romeri, an early-diverging dinosauromorph from the Late Triassic of New Mexico, is reported to lack ossified bone scars in the proximal portion of the femur that are present in other archosaurs. Bone scars are important phylogenetic characters, and increase in number and size during ontogeny in many extant reptiles. In this study, we tested whether this absence of scarring is indicative of the skeletal immaturity of the reported specimens, or if this lack is an evolutionary novelty. Morphological data from a growth series of six femora of D. romeri (96.9 mm – 136.6 mm long) and samples of bone tissue of one femur and one tibia were taken. The histology of the sampled femur showed characteristics of a skeletally immature individual, with a vascularized bone surface and one double annual line of arrested growth (LAG); however, this LAG may indicate the cessation of growth. The sampled tibia is from an individual with the largest femur in the growth series, but this tibia did not possess LAGs, suggesting that size is not strictly correlated with ontogenetic age in this taxon. D. romeri does not deposit ossified femoral muscle scars during ontogeny, and histology serves as the only method of assessing maturity. Whereas muscle scarring can be an additional sign of skeletal maturity, lack of scarring does not necessarily indicate skeletal immaturity. Ontogenetic changes may not be conserved across Archosauriformes, and implementing both histological and morphological data is essential to correctly understand ontogenetic patterns in this clade.

POS1-131  7:30 pm  Body mass estimation of juvenile individuals: towards a better understanding of extinct animal growth. Chiba K*, University of Toronto; Evans DC, Royal Ontario Museum; Campione NE, Uppsala University
Abstract: Growth curves can provide important insights into animal physiology and ecology and are of interest to paleobiology. Growth curves of extinct animals, however, rely entirely on three estimated parameters: 1) age of individual; 2) adult body mass; and 3) juvenile body mass. Recent studies have developed elaborate age retrocalculation methods to estimate the number of ontogenetically-obliterated growth marks and accurate body mass estimation methods of adults from intraspecific limb scaling. For mass estimation of juveniles, a previous study noted that intraspecific scaling patterns need not follow interspecific ones, and proposed a simple geometric scaling (length∝mass3) method, called Developmental Mass Extrapolation (DME), for estimating the mass of juveniles. Despite its merits, DME has not been empirically tested thoroughly, which questions the accuracy of growth curve reconstructions in extinct tetrapods. In order to assess DME, juvenile masses of four extant model taxa (Alligator mississipiensis, Iguana iguana, Procyon lotor, and Struthio camelus) are estimated using DME and an interspecific limb scaling equation. Estimated and actual masses are compared using mean percent prediction errors (PPEs). Mass estimates are based on a dataset of linear limb measurements (femur circumference and total length) and body mass. The results reveal lower PPE values when DME is used compared to the interspecific equation. These indicate that 1) intraspecific scaling approximates geometrically similarity, and 2) supports the use of DME to estimate the mass of juveniles in various tetrapod taxa. However, bivariate plots show systemic biases in DME (e.g., Procyon lotor) that are attenuated by using femoral circumference, rather than the total length. This study reveals critical insights into the uncertainty surrounding growth curve reconstructions in extinct forms with implications for understanding the biology of extinct animals.

POS1-133  7:30 pm  The calcar: a novel hindlimb structure in bats. Stanchak K.E.*, University of Washington, Department of Biology; Santana S.E., University of Washington, Department of Biology
Abstract: The evolution of the mammalian skeleton is a fascinating story of adaptation and specialization. Mammalian bones have often been co-opted for new and divergent purposes, resulting in significant morphological diversity. In several clades, the number of bones has been reduced, allowing for increased locomotor performance. Here we describe a rare case of skeletal addition in mammals—the calcar, an ancestral hindlimb feature of Chiroptera that is often used in taxonomic classification but is poorly understood in terms of its anatomy and function. Bats use their hindlimbs for many tasks, including flight, roosting, and prey capture. These functions vary extensively across bat species. We hypothesize that the bat calcar is a novel skeletal feature in mammals, and that its tissue and morphological structure correspond with specialized function and ecology. We explore this hypothesis with comparative histology and 3D morphological descriptions of the calcar and tarsals across several species. Consistent with previous research, the calcar is often a mineralized cartilaginous element that projects medially from the calcaneum into the hindlimb membrane. However, we found evidence of calcar ossification in at least one bat species, Noctilio leporinus, which raises questions about the homology of the calcar among mammalian tarsals. We also describe a surprisingly high morphological diversity among bats in both calcars and calcanea that might be associated with differences in hindlimb function.

POS1-135  7:30 pm  Compressive behavior of vertebral bodies in cetaceans (Delphinidae) and Sirenians (Trichechidae) . Ingle DN*, Florida Atlantic University; Porter ME, Florida Atlantic University
Abstract: The axial skeleton of fully aquatic mammals is a key anatomical feature powering locomotion. Body deformation is mediated by the mechanical properties of the vertebral column and surrounding non-osseous tissues, force production of swimming muscles, and the interaction of the body with water. Vertebral column stiffness, the ability to resist bending, varies regionally and increases rostro-caudally. We are investigating mechanical properties of vertebral bodies in two groups of marine mammals, cetaceans and sirenians, to understand how bones respond to force. The goals of the present study are to (1) assess yield strengths (stress at the elastic to plastic transition) and elastic moduli (resistance to compression) in the rostro-caudal plane of vertebral bodies; (2) compare yield strength and elastic moduli by functional location and vertebra anatomy, and (3) measure apparent density in the rostro-caudal plane of vertebral bodies to estimate microarchitecture. Vertebrae from the thoracic, lumbar, and caudal regions were sampled from the Florida manatee (Trichechus manatus latirostris; Sirenia) and melon-headed whale (Peponocephala electra; Cetacea). Soft tissue and bony projections from the vertebral body were removed with a bone saw and sander to isolate the vertebral body. Vertebral bodies were tested under a compressive load at a displacement rate of 0.05 in/min until the sample transitioned from the elastic to plastic region of deformation. The yield strength of the thoracic vertebra of the melon-headed whale was nearly double that of the Florida manatee. The melon-headed whale thoracic vertebral body was more than four times stiffer than the Florida manatee. However, the apparent density of the Florida manatee was double that of the melon-headed whale. These values indicate that bone in the melon-headed whale has structurally adapted to withstand higher forces in locomotion.

POS1-137  7:30 pm  Bone architecture in the rabbit (Oryctolagus cuniculus) mandible as a function of load and age. Rafferty K.L.*, University of Washington; Salamati A., University of Washington; Cunningham C., University of Washington; Shin D.U., University of Washington; Herring S.W., University of Washington
Abstract: Although the vertebrate head skeleton is not loaded by body weight, the jaws are subject to large forces from contraction of masticatory muscles and occlusion of teeth. Presumably loading influences architecture in these bones as it does the postcranial skeleton. We reduced mandibular loading in 5.5-month-old adult female rabbits by injecting one masseter with botulinum neurotoxin A (BoNT/A) once (endpoints 4 weeks or 12 weeks after injection) or three times with a 12-week recovery after each (total 36 weeks). Control animals received saline. The mandibles were examined histologically and with microCT. Bone loss was seen on both sides of the mandibular body and more dramatically at the condyle of the BoNT/A-injected side at 4 weeks. At 12 weeks, when muscle activity and force were near normal, partial bone recovery had occurred. The mandibular body no longer showed statistically significant differences between BoNT/A and saline rabbits, but after 3 injection-recovery cycles, the loss was again clear (p<0.02). A similar but more extreme pattern was seen for the BoNT/A-side condyle, which lost more bone and recovered more slowly, showing a slight additive effect in the 36-week group. Interestingly, the control as well as the BoNT/A mandibles had lower bone density in the 36-week animals than in the 4- and 12-week animals. Indeed, the internal architecture of the condyles after the 36-week experiment was quite different than after the shorter experiments. There was far less trabecular bone, and the condylar cartilage was underlaid by compact rather than spongy bone. We interpret these observations as age effects. The 36-week rabbits were 6-8 months older than those of the 4- and 12-week experiments. Although the transition of trabecular bone to cortical bone may indicate maturation rather than senescence, the generalized decrease in bone density suggests senescence. Thus both loading and age affect bone quality in the rabbit mandible. Funded by NIH DE018142.

POS1-139  7:30 pm  Bone microstructure of Bathyergus suillus (Rodentia: Bathyergidae): cortical bone thickening and sexual dimorphism. Montoya-Sanhueza G*, Department of Biological Sciences, Private Bag X3, Rhodes Gift 7701, University of Cape Town, South Africa; Chinsamy-Turan A, Department of Biological Sciences, Private Bag X3, Rhodes Gift 7701, University of Cape Town, South Africa
Abstract: Given that patterns of bone development in mammals are mostly known for cursorial animals, there is a considerable gap in our understanding of how other lifestyles affect bone growth. In addition, scarce research has been done on wild mammal populations, and these often include few individuals and incomplete ontogenetic series. This study examines the limb bone microstructure of a feral population of Bathyergus suillus (n=49), an endemic and solitary subterranean rodent from the Western Cape of South Africa. Undecalcified cross sections from the diaphysis of femur, humerus, tibia-fibula, ulna and radius through ontogeny were studied, and additional histomorphometric analyses were performed. Cortical bone thickening occurs mainly by periosteal apposition of zonal bone (fibrolamellar, parallel fibered and lamellar bone tissues) and limited endosteal resorption was observed. Midcortical areas with woven and compact coarse cancellous bone tissues also contributed to the cortical thickening. Mid-diaphyses were well vascularized during ontogeny, especially in juvenile stages, although secondary reconstruction was minor. Thickening of the compacta is evident from larger juveniles, although it is unclear if these changes are coupled with the attainment of sexual maturity and/or dispersion from nest. Histomorphometric analysis showed sexual dimorphism in femoral and humeral cortical porosity, with females having higher levels of intracortical resorption. The shape and size of resorption cavities also indicates sexual differences in mineral homeostasis. These findings contrasts with the generally high levels of resorption and remodeling documented in cursorial vertebrates. This study provides much insight into sexual differences of B. suillus, and provides fresh insight into how the subterranean lifestyle impacted on bone growth and development.

POS1-141  7:30 pm  Effects of selection for high wheel running on femoral nutrient foramen dimensions. Schwartz NL*, California State University San Bernardino; Horner AM, California State University San Bernardino; Garland T, University California Riverside; Patel BA, University Southern California
Abstract: Genetic composition is the blueprint from which bone is built, affecting over 50% of overall bone mineral content in adult mammals. However, stress from mechanical loading causes micro-fractures in bones, triggering dynamic bone remodeling by shifting the balance of absorption and formation to net formation. This remodeling is limited by supply of blood through the nutrient artery, which supplies 50-70% of total blood volume in long bones. The nutrient artery is limited in size by the nutrient foramen that it penetrates. Because genetic and environmental factors can independently affect the structure of bone, we used mice from lines that have been selectively bred for high levels of voluntary wheel running (High Runner, or HR lines) to determine whether a difference in nutrient foramen size in long bones was present in mice selectively bred for increased voluntary running (11th and 72nd generations). Femoral foramen, cortical thickness of the diaphysis, length, volume, moment of inertia, and polar moment were measured via micro-computed tomography. We use the data to test the effects of selection (HR vs control), exercise (wheel access vs sedentary), and potential interactions between them (HR vs control with wheel access).

POS1-143  7:30 pm  Comparison of impact loading and wheel running on femoral cross-section morphology in young outbred mice. Smolinsky AN*, University of Missouri, Columbia; Middleton KM, University of Missouri, Columbia
Abstract: The mechanostat hypothesis holds that long bones adapt to loading by increasing cortical thickness in areas that experience high strain and resorbing bone that experiences little strain, thus optimizing strength and weight. While exercises such as jogging or jumping are known to alter the cross-sectional dimensions of limb bones in vertebrates, we do not fully understand the relative contributions of ground reaction force (GRF) and muscle force in producing strains that lead to increased bone deposition with exercise. To examine the influence of loading environment on bone cross-sectional geometry, we exposed 4-week old, outbred ICR mice to one of three loading regimes for 21 days (n = 10 per group): impact loading to increase GRF to 6-10 body masses by dropping from a height of 25cm 10x per day, voluntary wheel running to increase both GRF and muscle-induced loading, or controls left undisturbed in their home cages. Undecalcified femoral mid-diaphyseal cross-sections were mounted, polished, photographed, and digitally silhouetted for analysis of cross-sectional properties. Standardized major axis regression against body mass demonstrates that the impact loading group had significantly greater cross-sectional areas, moments of inertia, and polar moments of inertia than control mice, while the running group showed no increase in cross-sectional dimensions relative to controls. Anteroposterior and mediolateral diameters and sectional moduli did not significantly differ between treatment groups. These results demonstrate that daily impact loading is more effective at altering bone cross-sectional properties than moderate to high levels of voluntary running. We conclude that further investigation is needed regarding the roles of GRF and muscle-induced forces in long bone modeling and the upper threshold of exercise duration effective for altering cross-sectional geometry, particularly in the context of voluntary locomotion.

POS1-145  7:30 pm  Effects of disrupting the dental lamina and mandibular nerve on tooth replacement in the green iguana (Squamata: Iguana iguana): A reanalysis of historic radiograph data. Brink K.S.*, University of British Columbia; Richman J.M., University of British Columbia
Abstract: The use of reptiles as amniote model organisms in the study of tooth development has become more common in recent years. The usefulness of the reptile model for studies of tooth replacement was developed in the 1960s by A.G. Edmund of the Royal Ontario Museum, Canada. In a series of prescient studies on tooth development, Edmund performed several surgeries on individuals of Iguana iguana to examine the effect of tooth removal and injury to soft tissues on tooth replacement patterns. Results of these experiments were never published, although mention was made that damage and wear do not affect the rate and pattern of tooth replacement. Combinations of surgeries included tooth extraction, removing small portions of the mandibular nerve with and without tooth extraction, and removal of portions of the dental lamina with and without tooth extraction. Surgeries were performed on one or two quadrants of the mouth and were monitored for up to six months post-surgery through bi-monthly radiographs (n = 8). When only tooth removal was carried out, successional teeth erupted normally after six months. In individuals where only the mandibular nerve was severed, tooth replacement rates and patterns also appeared to be unaffected. Interestingly, in individuals where teeth were removed and the mandibular nerve was severed, teeth were continuing to be replaced, although with abnormal timing and patterning. Complete cessation of tooth replacement occurred when the dental lamina was damaged or removed. These results suggest that there is an interaction between the mandibular nerve and the tooth replacement process. However, tooth replacement cycles are very long in the iguana and the brevity of data collection may have missed a later phenotype. Hence, experiments will be repeated in the leopard gecko (Squamata: Eublepharis macularis) over longer time periods to determine whether there is role for the mandibular nerve in tooth replacement in reptiles.

POS1-147  7:30 pm  Comparative assessment of enamel tufts. Kelly MA*, Saint Michael's College; Kempainen A, Saint Michael's College; Ledue N, Saint Michael's College; Constantino PJ, Saint Michael's College
Abstract: Teeth have the ability to adapt to diet through variation in shape, size, enamel thickness, prism decussation, and through the potential protective mechanism provided by enamel tufts. Tufts are hypocalcified, protein-filled fissures with a wavy-like appearance that extend outward from the enamel-dentine junction (EDJ) and between the organic sheaths that define enamel prisms. Initially, tufts were believed to be the undesirable byproducts of tooth development with no real function or value to the tooth. However, tufts are now believed to help protect teeth from catastrophic tooth failure through the mechanism of stress-shielding. Through this proposed mechanism, tufts absorb tensile stresses that build up along the EDJ during loading of the enamel and help protect teeth from large-scale fracture. If true, one would expect to find tufts primarily in animals that eat hard foods and/or apply high stresses to their teeth. However, almost nothing is known about the phylogenetic distribution of tufts in non-humans. We examined more than 25 species of carnivorans, primates, and suoids (pigs and peccaries) to determine tuft presence/absence. When tufts were present, we collected data on their distribution, density, length, and angle relative to the occlusal surface. Only humans, sea otters, and suoids featured tufts. The hypothesis that tufts are solely related to high tooth stresses is challenged by the absence of tufts in animals like wolverines and hyenas. Likewise, phylogenetic determinism does not explain the presence of tufts in sea otters but no other carnivorans. It appears that tufts are only present in animals that experience high tooth stresses and have a bunodont tooth form. Other notable findings include an inverse relationship between tuft length and density, and a different spatial arrangement of tufts in suoids compared to humans and sea otters.

POS1-149  7:30 pm  Enamel decussation patterns in carnivorans. Kempainen A*, Saint Michael's College; Ledue N, Saint Michael's College; Kelly MA, Saint Michael's College; Constantino PJ, Saint Michael's College
Abstract: Mammalian tooth enamel is comprised of large numbers of elongate crystalline prisms running from the enamel-dentine junction (EDJ) to the outer enamel surface (OES). In some species, these prisms run in a straight line, but in others they wave, so much so that prisms appear to crisscross (‘decussate’). The changing orientation of enamel prisms across the tooth crown results in an optical illusion of varying light and dark bands known as Hunter-Schreger Bands (HSB). The larger the number of HSBs in a given region of the enamel, the more intense is the decussation. High HSB packing densities have been proposed as a crack-stopping mechanism to prevent catastrophic fracture of the tooth crown. If decussation is influenced by natural selection, then we hypothesize that species with harder diets would feature greater HSB packing densities than those with softer diets. We tested this in premolar and molar teeth from nineteen carnivoran species ranging in body mass and diet. Teeth were sectioned buccolingually through the most mesial cusps and polished for microscopic observation. HSB packing densities were determined in longitudinal section by counting the number of HSB bands per millimeter parallel to the EDJ. HSBs also differ qualitatively in form, being either undulating, acute-angled, or with a zig-zag. We also examined the relationship of this with diet. Our results indicate no trend between HSB packing density and diet. Instead, HSB packing density correlates predominately to species body mass, with smaller species showing greater packing density. This is in contrast to several earlier studies on non-carnivorans that suggested larger-bodied species show greater decussation due to the increased bite forces they can produce. However, we did confirm the results of other earlier studies that showed that HSB type correlates with diet, with increasing degrees of prism waviness associated with harder diets.

POS1-151  7:30 pm  The role of enamel thickness in carnivoran dietary adaptation. Ledue N*, Saint Michael's College; Kelly MA, Saint Michael's College; Kempainen A, Saint Michael's College; Constantino PJ, Saint Michael's College
Abstract: Thick tooth enamel has been argued to protect against both fracture and wear of the tooth crown. Hard foods can cause tooth fracture because they are loaded with high axial forces perpendicular to the occlusal surface. Tough foods require shear to break down and tend to result in the loss of enamel through wear. Given the reportedly high incidence of tooth fracture among members of the Order Carnivora, and the purported relationship between tooth fracture and hard foods, we examined several carnivoran species to see whether they vary in enamel thickness, and if so, whether that variation is primarily a reflection of their need to prevent tooth fracture. We compared enamel thickness among a sample of twenty carnivoran species ranging in diet and body size. We hypothesized that species with harder foods in their diets will have both absolutely and relatively thicker tooth enamel. Average enamel thickness was digitally recorded from buccolingual sections made at primary cusps of minimally-worn premolars. We found that absolute measures of average enamel thickness do correlate with the presence of hard foods in the diet. Sea otters (Enhydra lutris) and spotted hyenas (Crocuta crocuta) had thicker enamel than any other carnivore included in this study, reflective of their regular consumption of hard-shelled invertebrates and mammalian bone, respectively. Sea otter enamel was more than four and a half times as thick as that of the closely related river otter (Lontra canadensis), while hyena enamel was 65% thicker than that of larger-bodied lions that hunt similar prey. Sea otter and hyena enamel thicknesses remain relatively high when corrected for body mass. The small-bodied Asian mongoose, which consumes hard-shelled crustaceans and mollusks, was also found to have relatively thicker enamel than the other carnivorans in our study.

[back to schedule]