A taxonomic revision of the genus Procolophon and the phylogenetic relationships of Procolophonoid reptiles

• Main Author: Martinez, Juan Carlos Cisneros
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: Procolophon; parareptiles; phylogeny; Gondwana; Triassic; Candelaria; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10539/4676

ABSTRACT This study presents a taxonomic revision of some procolophonoid parareptiles and a detailed, global analysis of procolophonid intrarelationships. The poorly known genus Candelaria, from the Middle Triassic of Brazil, is identified on the basis of new material as an owenettid, rather than a procolophonid as previously thought. Thus, Candelaria represents the youngest owenettid and the first member of this group from South America. The cranium of Candelaria is also remarkable for having temporal fenestrae, and the significance of this character within the Parareptilia is discussed. Based on a comprehensive review of specimens referred to different Procolophon species, it is proposed that only the type species, Procolophon trigoniceps, is valid. Thus, Procolophon specimens from Brazil, South Africa, and Antarctica are all referable to P. trigoniceps. Consequently, P. trigoniceps has one of the broadest known geographic ranges among Triassic tetrapod species. A comprehensive cladistic analysis of procolophonids more firmly resolves the relationships within that group. The analysis reveals that Procolophoninae and Leptopleuroninae are valid monophyletic groups, whereas Spondylolestinae is paraphyletic. The species formerly assigned to the genus ‘Thelegnathus’ from the Middle Triassic of South Africa, and those assigned to ‘Eumetabolodon’ from the Lower-Middle Triassic of China, are paraphyletic. The poorly known Spondylolestes from the Dicynodon Assemblage Zone of South Africa is considered valid and possibly represents the only Permian procolophonid in Gondwana. A new species, Kitchingnathus untabeni, is identified in the Lystrosaurus Assemblage Zone of South Africa. It is a basal member of the Procolophonidae and co-occurs with Procolophon in the Upper Katberg Formation. The new taxon is characterized by the presence of a large number of thin, bicuspid teeth. Character optimisation indicates that bicuspid teeth were acquired independently in K. untabeni, and hence originated twice during procolophonid ...