Abstract

Pterosaurs were important flying vertebrates for most of the Mesozoic, from the Late Triassic to the end of the Cretaceous
(225–65 Ma). They varied enormously through time in overall size (with wing spans from about 250 mm to about 12 m), and
in features of their cranial and postcranial skeletons. Comparisons of disparity based on discrete cladistic characters show
that the basal paraphyletic rhamphorhynchoids (Triassic–Early Cretaceous) occupied a distinct, and relatively small, region
of morphospace compared to the derived pterodactyloids (Late Jurassic–Late Cretaceous). This separation is unexpected,
especially in view of common constraints on anatomy caused by the requirements of flight. Pterodactyloid disparity shifted
through time, with different, small portions of morphospace occupied in the Late Jurassic and Late Cretaceous, and a
much larger portion in the Early Cretaceous. This explosion in disparity after 100 Ma of evolution is matched by the
highest diversity of the clade: evidently, pterosaurs express a rather ‘top heavy’ clade shape, and this is reflected in delayed
morphological evolution, again an unexpected finding. The expansion of disparity among pterodactyloids was comparable
across subclades: pairwise comparisons among the four pterodactyloid superfamilies show that, for the most part, these
clades display significant morphological separation, except in the case of Dsungaripteroidea and Azhdarchoidea. Finally,
there is no evidence that rhamphorhynchoids as a whole were outcompeted by pterodactyloids, or that pterosaurs were driven
to extinction by the rise of birds.