a1 Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, South Africa
The phylogenetic intrarelationships of procolophonid parareptiles are determined via a comprehensive cladistic analysis using a data matrix of 21 taxa and 58 characters. Most taxa are included for the first time in a phylogenetic analysis and 27 characters are novel. The relationships within the group are more firmly resolved than in previous analyses. Procolophoninae and Leptopleuroninae, two of the three traditional subdivisions of the Procolophonidae, are valid monophyletic groups, but Spondylolestinae is polyphyletic. The Chinese genera Pentaedrusaurus and Neoprocolophon are the most primitive members of the Leptopleuroninae. A new group, Theledectinae, is erected. The latter clade consists of small procolophonids with a reduced marginal dentition and wide bulbous monocuspid teeth. Eumetabolodon from China and the former genus ‘Thelegnathus’ from South Africa are shown to be polyphyletic. The successful radiation of the Procolophonidae during the Triassic is likely to be related to the development of feeding adaptations that allowed exploration of various ecological niches, particularly the exploitation of high-fibre herbivory. The scarcity of Permian records of procolophonids is examined and the genus Spondylolestes from the Upper Permian of South Africa is considered to be a valid taxon with procolophonid affinities. Finally, a review of the records from the Middle and Upper Triassic reveals a procolophonid global hiatus of more than 15 Ma in Ladinian–Lower Carnian rocks.