Congenital Malformations of the Vertebral Column in Ancient Amphibians |
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| Authors: | F Witzmann B M Rothschild O Hampe G Sobral Y M Gubin P Asbach |
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| Institution: | 1. Museum für Naturkunde, Leibniz‐Institut für Evolutions‐ und Biodiversit?tsforschung, , Berlin, D‐10115 Germany;2. Biodiversity Center, University of Kansas, , Lawrence, KS, 66045 USA;3. Paleontological Institute, Russian Academy of Sciences, , Moscow, 117868 Russia;4. Department of Radiology, Charité – Universit?tsmedizin Berlin, , Berlin, 10117 Germany |
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| Abstract: | Temnospondyls, the largest group of Palaeozoic and Mesozoic amphibians, primitively possess rhachitomous vertebrae with multipartite centra (consisting of one horse‐shoe‐shaped inter‐ and paired pleurocentra). In a group of temnospondyls, the stereospondyls, the intercentra became pronounced and disc‐like, whereas the pleurocentra were reduced. We report the presence of congenital vertebral malformations (hemi, wedge and block vertebrae) in Permian and Triassic temnospondyls, showing that defects of formation and segmentation in the tetrapod vertebral column represent a fundamental failure of somitogenesis that can be followed throughout tetrapod evolution. This is irrespective of the type of affected vertebra, that is, rhachitomous or stereospondylous, and all components of the vertebra can be involved (intercentrum, pleurocentrum and neural arch), either together or independently on their own. This is the oldest known occurrence of wedge vertebra and congenital block vertebra described in fossil tetrapods. The frequency of vertebral congenital malformations in amphibians appears unchanged from the Holocene. |
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