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Session Schedule & Abstracts

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Thursday 30th June, 2016

Sensory Biology & Neuroscience 1

Room: Salon F   9:30 am–11:00 am

Moderator(s): Bird DJ, Clement AM
SBN1-1  9:30 am  Using the brain-neurocranial relationship in the extant Australian lungfish to interpret fossil endocasts. Clement AM*, Flinders University; Strand R, Uppsala University; Nysjö J, Uppsala University; Long JA, Flinders University; Ahlberg PE, Uppsala University
Abstract: Lungfish first appeared in the geological record over 410 million years ago, and are the closest living group of fish to the tetrapods (limbed animals and their descendants). Palaeoneurological investigations into the group show that unlike numerous other fishes -but more similar to that in tetrapods- lungfish appear to have had a close fit between the brain and the cranial cavity that housed it. As such, researchers can use the endocast of fossil taxa (an internal cast of the cranial cavity) both as a source of morphological data but also to aid in developing functional and phylogenetic implications about the group. Using fossil endocast data from an exceptionally and 3D-preserved Late Devonian lungfish from the Gogo Formation, Rhinodipterus, and the brain-neurocranial relationship in the extant Australian lungfish, Neoceratodus,, we present the first virtually reconstructed brain of a fossil lungfish. Computed Tomographic data and a newly developed ‘brain-warping’ method are used in conjunction with our own distance map software tool to both analyse and present the data. The brain reconstruction is adequate, but we envisage that its accuracy and wider application in other taxonomic groups will grow with increasing availability of tomographic data sets.

SBN1-2  9:45 am  Comparative morphology of snake (Squamata) endocasts: evidence of phylogenetical and ecological signals. Allemand R.*, 1Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, CR2P - UMR 7207 - CNRS, MNHN, UPMC, Muséum National d’Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier, CP38, F-75005, Paris, France; Boistel R., IPHEP-UMR CNRS 6046, UFR SFA, Université de Poitiers, 40 avenue du Recteur Pineau, F-86022, Poitiers, France; Blanchet Z., UMR 7179 – CNRS / Muséum National d’Histoire Naturelle, Département Ecologie et Gestion de la Biodiversité, 57 rue Cuvier, CP55, F-75005, Paris, France; Cornette R., Institut de Systématique, Evolution, Biodiversité, ISYEB – UMR 7205 – CNRS, MNHN, UPMC, EPHE, Muséum National d’Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier, CP50, F-75005, Paris, France; Bardet N., Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, CR2P - UMR 7207 - CNRS, MNHN, UPMC, Muséum National d’Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier, CP38, F-75005, Paris, France; Vincent P., Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, CR2P - UMR 7207 - CNRS, MNHN, UPMC, Muséum National d’Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier, CP38, F-75005, Paris, France; Houssaye A., UMR 7179 – CNRS / Muséum National d’Histoire Naturelle, Département Ecologie et Gestion de la Biodiversité, 57 rue Cuvier, CP55, F-75005, Paris, France
Abstract: Endocasts obtained from computed tomography are now widely used in the field of comparative neuroanatomy. They provide an overview of the brain morphology and the associated tissues located in the cranial cavity, and thus, through anatomical comparisons, information about the senses, the behaviour and the ecology of the species. Although there are many studies dealing with mammal and bird endocasts, those performed on the endocasts of squamates are comparatively rare, thus limiting our understanding of their morphological variability and interpretations. Here, we provide the first comparative study of snake endocasts, in order to bring new information about the morphology of this structure and to test if it encompasses an ecologic signal. For this purpose, the digital endocasts of 45 snake specimens, encompassing a wide diversity of snakes in terms of phylogeny and ecology, were digitized using computed tomography, and compared both qualitatively and quantitatively (using traditional morphometrics). Snake endocasts present a great variability. Beyond a strong phylogenetical signal, the endocast morphology reflects some notable ecological trends: e.g., 1) fossorial species present a reduction of the optic roof; 2) both fossorial and marine species have cerebral hemispheres with a small lateral projection; 3) cerebral hemispheres are more developed in arboreal and terrestrial species. This study provides the first elements of comparative neuroanatomy in snakes, and shows that this structure, as in mammal and bird endocasts, carry both phylogenetical and ecological information.

SBN1-3  10:00 am  The bones and genes of smell: Cribriform morphology and olfactory receptor gene repertoires. Bird DJ*, University of California Los Angeles; Hayden S, University College Dublin; Teeling EC, University College Dublin; Murphy WJ, Texas A&M; Fox Rosales LA, University of California Los Angeles; Hamid AK, University of California Los Angeles; Van Valkenburgh B, University of California Los Angeles
Abstract: Mammals are assumed to have a keen sense of smell. Yet, the mammalian olfactory system has undergone losses as well as gains throughout its evolutionary history, generating a diverse olfactory profile, morphological and molecular, across all orders. The anatomy of olfaction varies markedly in mammals and includes the complete loss of the olfactory bulb in toothed whales. Annotated genomes reveal that some species, such as the elephant, have experienced an expansion of their olfactory receptor (OR) gene repertoire, while others, such as the great apes have experienced strong reductions. OR genes code for specific odorant receptors types, each of which is found on thousands of sensory neurons distributed across the olfactory epithelium. For this reason, we hypothesize that there is a relationship between the relative number of OR genes and olfactory anatomy. To test this, we quantified cribriform plate (CP) morphology in 26 mammal species for which we know the total number of OR genes and percentage of non-functioning pseudogenes. The CP was chosen for two reasons: 1) its perforations offer a direct imprint of all olfactory innervation passing from the nose to the brain, and 2) the CP is retained in dry skull samples and fairly well preserved in fossils. Using high resolution CT scans and 3D imaging software we estimated the surface area of the CP as well as the cumulative cross-sectional area of its foramina. Preliminary results show a significant positive correlation between the number of functioning OR genes and cribriform plate morphology. A second molecular metric, percentage of pseudogenes, shows no relationship to CP size. This is interesting, given that the percentage of OR pseudogenes is regularly used in the literature as a predictor of the relative loss of olfactory function. The results of this study, when applied to the CP morphology of fossil mammalian skulls, may help us gain insight into the relative size of the olfactory subgenome in extinct species.

SBN1-4  10:15 am  A comparison of the fluid dynamics and odorant deposition of unsteady sniffing versus quasi-steady breathing in the nasal cavity of the coyote. Rygg A*, University of California, Los Angeles; Craven B, The Pennsylvania State University; Van Valkenburgh B, University of California, Los Angeles
Abstract: The mammalian nose is a complex organ responsible for conditioning and filtering of inspired air, as well as sensing chemicals in the environment. Most carnivores have a complex nose with a convoluted airflow path that increases surface area for respiratory heat and moisture exchange, and odorant deposition. The coyote, in particular, possesses a complex nasal airway with a significant amount of olfactory epithelium for its size, likely reflecting its enhanced olfactory ability. Physically, airflow and odorant deposition in the nose are the first steps that influence olfactory function. In this regard, previous studies have shown that unique airflow patterns develop in the canine nasal cavity during sniffing that are optimized for delivering odorants to the olfactory region. To date, however, no studies of mammalian olfaction have compared the influence of unsteady sniffing versus quasi-steady breathing on olfactory function. This is especially important given that most studies of nasal airflow and odorant deposition assume quasi-steady conditions and do not consider the unsteady effects of sniffing. In this work, we examine how the dynamics of sniffing influence nasal airflow patterns and the deposition of odorants in the nasal cavity of the coyote. A three-dimensional model of the coyote nose is reconstructed from high-resolution magnetic resonance imaging (MRI) scans, and used in computational fluid dynamics (CFD) simulations of airflow and odorant deposition for steady-state inspiration, steady-state expiration, and unsteady sniffing. A comparison of the nasal airflow patterns, flow distribution in the nose, and odorant deposition will be shown to elucidate the influence of sniffing on olfactory function.

SBN1-5  10:30 am  Nasal morphometry and airflow dynamics in a nocturnal primate, Nycticebus pygmaeus (Mammalia: Primates). Smith TD*, Slippery Rock University; Engel SM, Slippery Rock University; Craven BA, The Pennsylvania State University; DeLeon VB, University of Florida
Abstract: "Macrosmatic" mammals, those most highly adapted for olfaction, have dedicated olfactory regions within their nasal cavity, and segregated airstreams for olfaction and respiratory air-conditioning. Here we examine the distribution of olfactory surface area (SA) and nasal airflow patterns in the pygmy slow loris (Nycticebus pygmaeus), to determine whether their complex nasal cavities are similar to "macrosmats" such as canids. Using the head of one adult loris cadaver, we co-registered micro CT slices and histology sections to create a 3D reconstruction of the olfactory mucosa distribution. Histological sections were photographed and converted to binary images for morphometric and functional analyses using custom image processing software. CT reconstructions of bone coded for mucosa type reveal the loris has a complex olfactory recess (~19% of total nasal SA), with multiple olfactory turbinals. However, the first ethmoturbinal has a rostral projection that extends far anterior to the olfactory recess, and ~90% of the SA of this turbinal is covered with non-olfactory epithelium. A computational fluid dynamics simulation of airflow indicates that high speed flow is restricted medially, along the respiratory surfaces of the first ethmoturbinal and maxilloturbinal. The slowest moving airstreams are found laterally in paranasal regions and posteriorly within the olfactory recess. Moreover, some airflow that reaches the olfactory recess does not pass through the dorsal meatus. This pattern is notably different than reported for canids, in which olfactory airstreams are shunted through the dorsal meatus, separately from respiratory airstreams, to an olfactory recess in which all ethmoturbinals are mostly covered with olfactory epithelium. The results indicate that lorises may be said to have certain macrosmatic anatomical characteristics (e.g., olfactory recess), but not segregated nasal airflow patterns as in the dog. Funding: NSF BCS-1231717, BCS-1231350, IOS-1120375.

SBN1-6  10:45 am  Comparative morphology and histology of the nasal fossa in four mammals: gray squirrel, bobcat, coyote, and deer. Van Valkenburgh B.*, UCLA; Yee K.K., Monell Chemical Senses Center; Craven B.A., The Pennsylvania State University; Wysocki C.J., Monell Chemical Senses Center
Abstract: Comparative studies of the quantity and distribution of olfactory epithelium (OE) in mammals have been largely limited to species <1kg due to the difficulty of applying traditional histological approaches to larger specimens. Here we present data on olfactory and non-sensory tissue distribution in the nasal fossa of 4 mammals: gray squirrel, bobcat, coyote, and deer, ranging from 0.42 kg to 62 kg. These species were chosen because they could be acquired fresh from hunters in accordance with local regulations. Moreover, they exhibit a range of skull shapes and diets that might affect OE quantity and distribution. Nasal cavities were scanned using high-resolution MRI and then prepared for histological analysis. The noses were sectioned and OE was highlighted using staining and immunohistochemistry. On selected sections, the perimeters of the septum, maxilloturbinals, nasoturbinals and ethmoturbinals were measured using ImagePro Plus software. We quantified the total surface area of OE and non-sensory epithelium in the nasal cavity as well as its anatomical distribution. In all four species, OE was entirely absent from the maxilloturbinals and was confined to the caudal half of the nose on the septum, nasoturbinals, and ethmoturbinals. Total surface area of OE did not correlate well with body mass. Although the squirrel had the least OE, the similarly sized 15 kg coyote and 12 kg bobcat differed greatly in total OE surface area, with the canid having a much larger area comparable in extent to that of the 62 kg deer, suggesting greater olfactory ability in the canid. The gray squirrel differed from the other 3 species in having a much greater proportion of its nasal fossa lined with OE, which is similar to what has been observed in other small mammals. Our results suggest that both skull size and shape influence OE distribution, as has been shown for some primates.

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