Braincase and neuroanatomy of the lagerpetid Dromomeron gregorii (Archosauria, Pterosauromorpha) with comments on the early evolution of the braincase and associated soft tissues in Avemetatarsalia

Anat Rec (Hoboken). 2023 Oct 4. doi: 10.1002/ar.25334. Online ahead of print.ABSTRACTThe anatomy of the braincase and associated soft tissues of the lagerpetid Dromomeron gregorii (Archosauria: Avemetatarsalia) from the Late Triassic of the United States is here described. This corresponds to the first detailed description of cranial materials of Lagerpetidae, an enigmatic group of Late Triassic (c. 236-200 Million years ago) animals that are the closest known relatives of pterosaurs, the flying reptiles. The braincase of D. gregorii is characterized by the presence of an anteriorly elongated laterosphenoid and a postparietal, features observed in stem-archosaurs but that were still unknown in early members of the avian lineage of archosaurs. Using micro-computed tomography (CT-scan data), we present digital reconstructions of the brain and endosseous labyrinth of D. gregorii. The brain of D. gregorii exhibits a floccular lobe of the cerebellum that projects within the space of the semicircular canals. The semicircular canals are relatively large when compared to other archosauromorphs, with the anterior canal exhibiting a circular shape. These features of the sensory structures of D. gregorii are more similar to those of pterosaurs than to those of other early avemetatarsalians. In sum, the braincase anatomy of D. gregorii shows a combination of plesiomorphic and apomorphic features in the phylogenetic context of Archosauria and suggests that the still poorly understood earl...
Source: Anatomical Record - Category: Anatomy Authors: Source Type: research