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Session Schedule & Abstracts

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Thursday 30th June, 2016

General Morphology 3

Room: Salon C   2:30 pm–4:00 pm

Moderator(s): Bernardi M, Curtis AA
GEN3-1  2:30 pm  Primates hearing: ear morphology, functions and ecology. Bernardi M*, EPHE/UMR uB CNRS 6282; Couette S, EPHE/UMR uB CNRS 6282; Montuire S, EPHE/UMR uB CNRS 6282
Abstract: The morphology of the basi-cranial elements and especially the ear structures shape have been essentially studied for taxonomic and phylogenetic purposes. Due to the development of new acquisition techniques such as micro-computed tomography, new morphological data are available. Since the ear is the center of auditory capacity, new ear studies also provide additional information on hearing, allowing the identification of adaptations to specific environments. Previous works have already study the relationships between ear morphology and functions. The order Primates is the third most diverse order (number of species) of mammals, but also one whose life history traits, lifestyles, behaviors and social interactions are the more diverse. Hearing sensitivity is variable among primate’s species, suggesting an adaptive selection on this function related to socio-ecological parameters. However, intraspecific variation is almost never quantified. In this study, we measured 8 morphological variables of the middle and inner ear for 80 extant and extinct strepsirhines of 12 genera. Morphological and hearing parameters were quantitatively analyzed to compare intra- and inter-specific variations. Our morpho-functional results were compared to ecological and behavioral data, such as activity patterns and social organization. We also tested the effects of body size and phylogeny on ear morphology. The phylogenetic effect is not significant, however, our preliminary results show that the communication differs according to the population density. Thus, ear morphology is a relevant tool to assess ecological and behavioral characteristics. Assumptions are made on fossil species in order to estimate paleoecological and paleo behavioral parameters, directly from ear morphology.

GEN3-2  2:45 pm  Convergent loss of paranasal sinuses in mammals is explained by their deleterious effects on high-frequency communication. Foster F.R.*, Rutgers University; Shapiro D.F., Rutgers University
Abstract: Investigation of the evolutionary history of mammalian paranasal sinuses has generally focused on their origin and adaptive benefit. However, the pattern of convergent loss of these structures in a variety of mammalian species has been largely overlooked, or dismissed as a result of developmental effects that dominate after their presently non-adaptive role. Here, we test an alternative hypothesis for convergent loss of paranasal sinuses in mammals based on their potential effects on auditory communication. This draws upon previous work that has linked the evolution of paranasal sinuses with enhanced vocal communication in the low frequency range, where lower density structures in the cranium are suggested to act as amplifiers. In a complimentary way, paranasal sinuses may also negatively affect high frequency communication when the size of the cavity matches the wavelength, or corresponding whole wave number, of sounds resulting in destructive interference. Consequently, we suggest that convergent loss of paranasal sinuses may result from the selective pressure to eliminate these structures due to their deleterious effect in species that use high frequency communication. We collected data on optimal communication frequency range and presence/absence of paranasal sinuses in 62 mammalian species, and tested our hypothesis using phylogenetic least squares regression. Preliminary results support the hypothesis that destructive interference from paranasal sinuses in species that rely on high frequency communication created a selective pressure that led to their loss, but leaves room for alternative explanations for their loss in some taxa. Future studies should further refine our hypothesis by enhancing data on paranasal sinus size, location, and frequency range in a wider range of mammalian species.

GEN3-3  3:00 pm  Evolution of the laterosensory canals of the snout in Osteognathostomata (Vertebrata: Pisces). Rizzato P. P.*, LIRP-FFCLRP-USP; Bockmann F. A., LIRP-FFCLRP-USP
Abstract: The snout region of basal osteognathostomates has been subjected to many studies, most focusing on the homologization of bone elements. The laterosensory system of that region is usually used only as landmark for bone identity, but not as source of phylogenetic information. In order to fill this knowledge gap, we carried out comparisons, under a phylogenetic perspective, on the pathways of laterosensory canals on the snout of basal actinopterygians and sarcopterygians, both fossil and living. In the putative ancestral condition, the nasal canal passes longitudinally between the contralateral nares; its terminal portion may fuse to the anterior transverse commissure. In the most basal Sarcopterygii, the canal does not fuse to the anterior transverse commissure, although a connection is probably present in the common ancestor of Onychodontidae, Actinistia and Dipnomorpha. In the non-monophyletic, basal actinopterygian ‘palaeonisciforms’, the terminal portion of the nasal canal passes between the anterior and posterior nares. This condition may be interpreted as a synapomorphy of Actinopterygii, as is also present in Acipenseriformes. In Polypteriformes and Holostei, the nasal canal passes also between the anterior and posterior nasal openings but it has a lateroposteriorly directed curvature at its anterior portion. In Teleostei, a condition similar to the ancestral condition is present, but it is likely as a secondary acquisition, since the curvature is also present in larval stages of Salmo. Therefore, we concluded that the curvature at the anterior portion of the nasal canal was present on the common ancestor of Polypteriformes+Actinopteri but it has been reversed in Acipenseriformes and lost in adult teleosteans. A plate-like nasal bone is absent in Acipenseriformes, inasmuch as its nasal canal is entirely reduced to tubular ossicles, possibly a new synapomorphy for the order. This work was funded by FAPESP (#2015/10849-6) and CNPq (# 312067/2013-5).

GEN3-4  3:15 pm  Coos, booms, and hoots: the evolution of closed-mouth vocal behavior in birds. Riede T, Midwestern University; Eliason C*, The University of Texas at Austin; Miller E, Memorial University of Newfoundland; Goller F, University of Utah; Clarke J, The University of Texas at Austin
Abstract: Most birds vocalize with an open beak, but vocalization with a closed beak into an inflating cavity occurs in territorial or courtship displays in disparate species throughout birds. Closed-mouth vocalizations generate resonance conditions that favor low-frequency sounds. By contrast, open-mouth vocalizations cover a wider frequency range. Here we describe closed-mouth vocalizations of birds from functional and morphological perspectives and assess the distribution of closed-mouth vocalizations in birds and related outgroups. Ancestral-state optimization suggests that closed-mouth vocalizations are unlikely to be ancestral to birds and evolved independently at least 16 times within Aves. Origin of the trait is always preceded by an increase in body size. Closed-mouth vocalizations are also rare in the small-bodied passerines, further supporting a relationship of closed-mouth vocalization to body size. In light of the large body sizes of non-avian dinosaurs and conserved motor patterns associated with vocal behavior across tetrapods regardless of vocal organ, closed-mouth vocalizations were likely represented among extinct non-avian dinosaurs. As in birds, this behavior likely was limited to sexually selected vocal displays, and not used in all contexts in which vocalizations occur, and therefore would have co-occurred with open-mouthed vocalizations. It may have originated in response to selective pressures favoring low-frequency sounds.

GEN3-5  3:30 pm  The head suspension apparatus of cats and the shoulder suspension apparatus of humans: Modeling a macroevolutionary transformation with extant organisms. Osborn ML*, Louisiana State University School of Veterinary Medicine; Homberger DG, Louisiana State University
Abstract: The macroevolutionary processes that result in the origin of supraspecific taxa are commonly assumed to have resulted from an accumulation of minor morphological changes. To test whether small structural changes may have fundamental functional effects, we modeled the morphological and biomechanical changes necessary to transform the head-neck-shoulder apparatus of a quadrupedal mammal into that of the bipedal human. For our comparative analysis, we selected a cat as the representative quadruped because cats and humans are surprisingly similar in some aspects of their head-neck-shoulder morphology and postures. In both species, the head-neck-shoulder apparatus comprises the mastoid processes and nuchal region of the skull, the clavicles, a de facto nuchal ligament, and the sternocleidomastoid-trapezius muscle complex and its related fascias. The postures and force regimes of the head-neck-shoulder apparatus of a ready-to-pounce cat and a slumped-forward human are also similar in that the head is suspended from the cervical vertebral column by the nuchal ligament. As postures change to various extents, so do the musculo-fascio-skeletal configurations and, as a result, their force regimes. For example, the head-neck-shoulder apparatus in an upright human with freely hanging arms suspends the shoulders from the skull and does the same in a cat that is capable of sitting on its haunches with freely hanging forelimbs. Thus, minor morphological variations in skeletal proportions, joint morphology and attachments of ligaments and muscles, which together have significant biomechanical effects, result in the fundamental change of the head-neck-shoulder apparatus from a head suspension to a shoulder suspension in the same manner that can be assumed to have happened during the evolutionary transition from a quadruped to a biped.

GEN3-6  3:45 pm  Unique turbinal morphology in echolocation specialists (Chiroptera: Rhinolophidae). Curtis AA*, American Museum of Natural History; Simmons NB, American Museum of Natural History
Abstract: The mammalian nasal fossa contains a set of delicate and often structurally complex bones called turbinals. Turbinals and the epithelia they support function in regulating respiratory heat and water loss, as well as increasing surface area for olfactory tissue. Here, we used high-resolution microCT scanning to investigate a unique and previously undescribed turbinal morphology in 29 species from the bat family Rhinolophidae, which we compared with those of closely related hipposiderid and megadermatid bats, as well as with Pteropus lylei. Rhinolophids have one of the most highly derived echolocation systems known among bats, and exhibit numerous morphological characteristics associated with emission of high duty cycle echolocation calls via the nasal chamber. In these bats, we found that the maxilloturbinals and a portion of one of the ethmoturbinals contribute to form a pair of strand-like bony structures on each side of the nasal chamber. These structures project anteriorly from the transverse lamina and complete a hairpin turn to project posteriorly down the nasopharyngeal duct, and varied in length among the species in our sample. We hypothesize that these structures may play a role in sound transmission of echolocation calls since they are located directly along the path that sound travels between the vocal chords and external nares during call emission. The strand-like turbinals may additionally – or alternatively – play a role in reducing respiratory heat and water loss without greatly impacting echolocation behavior since cylindrical structures take up little space within the nasal fossa, but still have high surface area to volume ratios. The strand-like structure of the turbinals in Rhinolophidae are unique and represent a new diagnostic character for this family.

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