An external mandibular fenestra and other archosauriform characters in basal pterosaurs re-examined

Abstract

It was claimed that pterosaurs had external mandibular fenestrae, antorbital fossae and muscle scars homologous with the femoral fourth trochanter of archosauriforms, and that those characters suggested that the Pterosauria were within the clade Erythrosuchus + Archosauria. Pertinent parts of available specimens are described to confirm that one pterosaur had external mandibular fenestrae and one had antorbital fossae. However, arguments are presented that possession of external mandibular fenestrae does not support inclusion of the Pterosauria within the clade Erythrosuchus + Archosauria and that the antorbital fossae in the one pterosaur are not homologous with those of the clade Erythrosuchus + Archosauria. Arguments are also presented that the possession of a m. caudofemoralis scar by some pterosaurs does not support inclusion of the Pterosauria within the clade Erythrosuchus + Archosauria, whereas the lack of homologous antorbital fossae and a mound-like or aliform fourth trochanter supports exclusion of the Pterosauria from that clade.

Keywords::

• pterosaur
• phylogeny
• mandibular fenestra
• antorbital fossa
• fourth trochanter

Acknowledgements

The author thanks L. Steel and S. Chapman of the NHMUK, O. Rauhut and R. Liebreich of the BSP, Ü. Rehsteiner of the BNM, A. Downs of the GR, C. Sagebiel of the TMM and A. Paganoni of the MCSNB for access to specimens under their care, and S. Nesbitt for access to specimens on loan to him. The manuscript was reviewed by F. M. Dalla Vecchia, whose painstaking review led to many improvements, and several anonymous reviewers commented on earlier versions.

Disclosure statement

No potential conflict of interest was reported by the author.