Observations on the structure of the Early Permian reptile Stereosternum tumidum Cope

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dc.contributor.author Modesto, Sean Patrick
dc.date.accessioned 2015-01-12T07:53:12Z
dc.date.available 2015-01-12T07:53:12Z
dc.date.issued 1999
dc.identifier.issn 0078-8554
dc.identifier.uri http://hdl.handle.net/10539/16442
dc.description.abstract New information on the mesosaur Stereosternum tumidum is derived from a nearly complete skeleton and other material. Two autapomorphies are identified for Stereosternum: (1) presence of an ‘odontoid’ axial process, formed probably by co-ossification of the atlantal pleurocentrum to that of the axis, and (2) the presence of a posterior supraneural process on the neural arch of dorsal vertebrae. Temporal fenestration appears to be absent in Stereosternum, marginal teeth are determined to be subcircular rather than oval in cross section and in this respect resemble those of Mesosaurus, and there is no sign of fracture planes in the caudal vertebrae that could be indicative of caudal autotomy. A phylogenetic analysis, based on a slightly modified data matrix from the literature, identifies Mesosauridae as the sister group of Parareptilia within the reptilian clade Anapsida (sensu lato). As a consequence of this rearrangement of amniote tree topology, the stem-based taxon Sauropsida is regarded to be in abeyance, because it now includes exactly the same taxa as Reptilia. Mesosaurs, at more than 275 million years of age, can be recognised as the oldest known anapsid reptiles. en_ZA
dc.description.sponsorship The Council's Research Committe, University of the Witwatersrand; National Science Foundation en_ZA
dc.language.iso en en_ZA
dc.publisher Bernard Price Institute for Palaeontological Research en_ZA
dc.subject stereosternum en_ZA
dc.subject mesosaurs en_ZA
dc.subject Anapsida en_ZA
dc.subject phylogeny en_ZA
dc.subject permian en_ZA
dc.title Observations on the structure of the Early Permian reptile Stereosternum tumidum Cope en_ZA
dc.type Article en_ZA

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