Search for: All records

Abstract The trigeminus nerve (cranial nerve V) is a large and significant conduit of sensory information from the face to the brain, with its three branches extending over the head to innervate a wide variety of integumentary sensory receptors, primarily tactile. The paths of the maxillary (V₂) and mandibular (V₃) divisions of the trigeminus frequently transit through dedicated canals within the bones of the upper and lower jaws, thus allowing this neuroanatomy to be captured in the fossil record and be available to interpretations of sensory ability in extinct taxa. Here, we use microCT and synchrotron scans from 38 extant and fossil species spanning a wide phylogenetic sample across tetrapods to investigate whether maxillary and mandibular canal morphology can be informative of sensory biology in the synapsid lineage. We found that in comparison to an amphibian and sauropsid outgroup, synapsids demonstrate a distinctive evolutionary pattern of change from canals that are highly ramified near the rostral tip of the jaws to canals with increasingly simplified morphology. This pattern is especially evident in the maxillary canal, which came to feature a shortened infraorbital canal terminating in a single large infraorbital foramen that serves as the outlet for branches of V₂that then enter the soft tissues of the face. A comparison with modern analogues supports the hypothesis that this morphological change correlates to an evolutionary history of synapsid‐specific innovations in facial touch. We interpret the highly ramified transitional form found in early nonmammalian synapsids as indicative of enhanced tactile sensitivity of the rostrum via direct or proximal contact, similar to tactile specialists such as probing shorebirds and alligators that possess similar proliferative ramifications of the maxillary and mandibular canals. The transition toward a simplified derived form that emerged among Mid‐Triassic prozostrodont cynodonts and is retained among modern mammals is a unique configuration correlated with an equally unique and novel tactile sensory apparatus: mobile mystacial whiskers. Our survey of maxillary and mandibular canals across a phylogenetic and ecological variety of tetrapods highlights the morphological diversity of these structures, but also the need to establish robust form‐function relationships for future interpretations of osteological correlates for sensory biology. 

The Dicynodontia (Therapsida: Anomodontia) is one of the most successful Permo-Triassic terrestrial tetrapod clades and the oldest specimens are recorded from the middle PermianEodicynodonAssemblage Zone of South Africa. Their fossil record is abundant and species-rich across Pangea. By contrast, the fossil record of the basal-most anomodonts, which includes non-dicynodont anomodonts and early forms of dicynodonts, is patchy and their morphology and phylogeny are deduced from relatively few specimens. Discovered in 1982 and described in 1990, the holotype ofEodicynodon oelofseni(NMQR 2913) is one of the better-preserved early anomodont specimens. However, it has been suggested thatE. oelofsenidoes not belong to the genusEodicynodon. Here, using CT-scanning and 3D modeling, the skull ofEodicynodon oelofseni,Patranomodon nyaphuliiandEodicynodon oosthuizeniare redescribed. In the framework of this study, the application of 3D scanning technology to describe anatomical structures which were previously inaccessible in these fossils has enabled detailed redescription of the cranial morphology of the basal anomodontsPatranomodon,Eodicynodon oelofseniandE. oosthuizeniand led to a greater understanding of their cranial morphology and phylogenetic relationships. Based on an anatomical comparison and phylogenetic analyses (Bayesian and cladistics) the phylogenetic relationships of basal anomodonts are reassessed and it is suggested that NMQR 2913 does not belong to the genusEodicynodonbut likely represents a separate genus basal to other dicynodonts. A new genus is erected for NMQR 2913. This presents one of the first applications of Bayesian Inference of phylogeny on Therapsida. 

Abstract Fossil endocasts record features of brains from the past: size, shape, vasculature, and gyrification. These data, alongside experimental and comparative evidence, are needed to resolve questions about brain energetics, cognitive specializations, and developmental plasticity. Through the application of interdisciplinary techniques to the fossil record, paleoneurology has been leading major innovations. Neuroimaging is shedding light on fossil brain organization and behaviors. Inferences about the development and physiology of the brains of extinct species can be experimentally investigated through brain organoids and transgenic models based on ancient DNA. Phylogenetic comparative methods integrate data across species and associate genotypes to phenotypes, and brains to behaviors. Meanwhile, fossil and archeological discoveries continuously contribute new knowledge. Through cooperation, the scientific community can accelerate knowledge acquisition. Sharing digitized museum collections improves the availability of rare fossils and artifacts. Comparative neuroanatomical data are available through online databases, along with tools for their measurement and analysis. In the context of these advances, the paleoneurological record provides ample opportunity for future research. Biomedical and ecological sciences can benefit from paleoneurology’s approach to understanding the mind as well as its novel research pipelines that establish connections between neuroanatomy, genes and behavior.