Morphological diversity and biogeography of procolophonids (Amniota: Parareptilia)

A recent phylogenetic analysis of procolophonid parareptiles is used as the basis for a study of morphological diversity(disparity) in these amniotes. Disparity values are compared in three groups of procolophonids (a paraphyletic series ofbasal taxa and two monophyletic sister groups: procolophonines and leptopleuronines), two ecophenotypic assemblages(one based upon inferred diet – non high-fibre versus high-fibre species; the other based upon cranial sculpture – nonhorned versus horned species), and two temporal assemblages (Lower Triassic versusMiddle and Upper Triassic). The meandisparity values are comparable in the case of temporal and ecophenotypic assemblages. High-fibre species are marginallyless disparate than non high-fibre species. The combined Middle and Upper Triassic species are slightly less disparate thanLower Triassic species. Finally, horned species are only slightly more disparate than non-horned species. The paraphyleticseries of basal taxa and the leptopleuronines show similar disparity values, marginally higher than those for procolophonines.Phylogenetic analysis is also used to reconstruct the biogeographical history of procolophonids. Both ancestral area analysisand dispersal–vicariance analysis show that South Africa was the most likely ancestral area for procolophonids as a whole.North China – either as a single area or in combination with Russia or South Africa – was the most likely ancestral area forthe leptopleuronine–procolophonine clade.