Plagiosaurus

Abstract: The histology of the vertebral centrum of the morphologically diverse Temnospondyli is poorly known. In this study, the variability of the histological framework of various taxa from several Permian and Triassic localities was investigated for the first time. Twelve intercentra, forming the anterior part of the diplospondylous centra of temnospondyls, were examined histologically. The intercentra of all studied taxa share a highly vascularized cortex on the ventro-lateral side and primary and secondary trabecular, endochondral bone on the dorsal side. A high variability is present, among others, within the arrangement of the vascular cavities, the density of the trabeculae and the distribution of calcified cartilage. The Stereospondyli possess a high amount of calcified cartilage between the trabeculae, in all other taxa the calcified cartilage covers only the dorsal surface of the intercentrum. Among the plagiosaurids, despite morphological similarities, the intercentra show a different development. In Gerrothorax and Plagiosaurus, periosteal bone is also present on the dorsal side around the neural canal, tentatively indicating a fusion of pleurocentrum and intercentrum. The different histological framework of the investigated intercentra may indicate the phylogenetic value of intercentra microstructure, however further studies are necessary. The preservation of calcified cartilage between the trabeculae seems to be a paedomorphic character typical for all Stereospondyli. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 747–764. ADDITIONAL KEYWORDS: calcified cartilage – intercentrum – palaeohistology – periosteal bone – Temnospondyli – vertebrae.