Computed Tomography elucidates ontogeny within the basal therapsid clade Biarmosuchia

PeerJ

article

Aliénor Duhamel¹  Julien Benoit²  Michael Day²  Bruce Rubidge²  Vincent Fernandez⁴ 

[1] ENS de Lyon, CNRS, UMR 5276, LGL-TPE, Université Claude Bernard;Evolutionary Studies Institute, University of the Witwatersrand;School of Geosciences, University of the Witwatersrand;Department of Earth Sciences;European Synchrotron Radiation Facility

关键词: Synapsida;    Therapsida;    Biarmosuchia;    Ontogeny;    CT-scan;   

DOI  :  10.7717/peerj.11866

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Biarmosuchia is a clade of basal therapsids that includes forms possessing plesiomorphic ‘pelycosaurian’ cranial characters as well as the highly derived Burnetiamorpha which are characterised by cranial pachyostosis and a variety of cranial bosses. Potential ontogenetic variation in these structures has been suggested based on growth series of other therapsids with pachyostosed crania, which complicates burnetiamorph taxonomic distinction and thus it is essential to better understand cranial ontogeny of the Burnetiamorpha. Here, three new juvenile biarmosuchian skulls from the late Permian of South Africa are described using X-ray micro computed tomography (CT). We found that juvenile biarmosuchians are distinguished from adults by their relatively large orbits, open cranial sutures, and incomplete ossification of the braincase and bony labyrinth. Also, they manifest multiple centres of ossification within the parietal and preparietal bones. CT examination reveals that the holotype of Lemurosaurus pricei (BP/1/816), previously alleged to be a juvenile, shows no evidence of juvenility and is thus probably an adult. This suggests that the larger skull NMQR 1702, previously considered to be an adult L. pricei, may represent a new taxon. This study provides, for the first time, a list of characters by which to recognise juvenile biarmosuchians.

【 授权许可】

CC BY