THE PHYLOGENETIC POSITION OF THE PTEROSAURIA WITHIN THE ARCHOSAUROMORPHA

In recent years the hypothesis that pterosaurs were the major sister-g roup of dinosaurs and a closely-linked hypothesis that pterosaurs evol ved flight from the ground up have gained general acceptance. A cladis tic analysis of the Archosauromorpha using characters presented by pre vious workers results in a single most parsimonious tree with the Pter osauria as the major sister-group of the Dinosauria. However, that sis ter-group relationship is supported only by a suite of hindlimb charac ters that are correlated with bipedal digitigrade locomotion in dinosa urs. In pterosaurs the characters have been interpreted as correlates of bipedal cursorial locomotion, arboreal leaping, or involvement of t he hindlimb in the wing. The homology of those characters in dinosaurs and pterosaurs cannot be supported. Reanalysis of the data after excl usion of those hindlimb characters results in most parsimonious trees with the Pterosauria as the sister-group of the Erythrosuchidae + Prot erochampsidae + Euparkeria + Archosauria, in that order. This sister-g roup relationship is supported by a diverse assemblage of functionally independent skeletal characters from all regions of the skeleton. The results of the analysis cast doubt on the hypothesis that pterosaurs evolved flight from the ground up. (C) 1996 The Linnean Society of Lon don