Evolution of facial innervation in anomodont therapsids (Synapsida): Insights from X‐ray computerized microtomography

摘要: Anomodontia was the most successful herbivorous clade of mammalian stem lineage (non-mammalian synapsids) during late Permian and Early Triassic. Among anomodonts, Dicynodontia stands apart because presence an osseous beak that shows evidence insertion a cornified sheath, ramphotheca. In this study, fourteen anomodont specimens were microCT-scanned their trigeminal canals reconstructed digitally to understand origin evolution nerve innervation We show pattern "beak" is more similar in chelonians (the nasopalatine branch enlarged innervates premaxillary part ramphotheca) than birds (where maxillary branches play minor roles). The noticeably beak-less basal Patranomodon, suggesting could be or chainosaur synapomorphy. Our analyses suggest absence tusks postcanine teeth are often accompanied by corresponding variations rami innervating caniniform process alveolar region, respectively. degree ossification canal for nasal ramus ophthalmic also appears correlate with boss. absent from premaxilla Bidentalia as they uniquely large plexus formed internal instead. elongated shape Lystrosaurus supports hypothesis rostrum evolved elongation subnarial region snout. Finally, atrophied variable aspect Myosaurus genus had reduced upper