On the phylogeny and evolutionary history of pterosaurs

Abstract

Previous cladistic studies of pterosaur relationships suffer from restricted numbers of taxa and characters, incomplete data sets and absence of information on characters, tree structure and the robustness of tress. Parsimony analysis of a new character data set (60 characters, 20 terminal taxa, 97.75% complete) yielded six trees. In the strict consensus tree Preondactylus is the most basal taxon followed, stepwise, by the Dimorphodontidae and the Anurognathidae. Beyond this basal group, more derived pterosaurs (Campylognathoididae (Rhamphorhynchidae + Pterodactyloidea)) share a suite of characters principally associated with elongation of the rostrum. The Pterodactyloidea consists of four major clades. The Ornithocheiroidea is the most basal taxon consisting, stepwise, of Istiodactylus, the Ornithocheiridae, Nyctosaurus and the Pteranodontidae. The remaining taxa, Ctenochasmatoidea, Dsungaripteroidea and Azhdarchoidea, are weakly united in a clade of non-ornithocheiroid pterodactyloids, but their inter-relationships are difficult to resolve. Cycnorhamphus is the basal-most ctenochasmatoid, while the remaining taxa (Pterodactylus, Lonchodectidae, Ctenochasmatidae) form an unresolved trichotomy. The Dsungaripteroidea (Germanodactylus+Dsungaripteridae) is strongly supported by features of the skull and dentition. The Azhdarchoidea (Tapejara [Tupuxuara + Azhdarchidae]) is united by cranial characters such as elevation of the antorbital region, and relative shortening of the wing finger. The pattern of pterosaur evolution suggested by the results of this analysis is broadly similar to traditional ideas, but has greater resolution, more complexity and reveals several previously unrecognized ‘events’.

A pterodactyloid pterosaur from the Upper Cretaceous Lapurr sandstone, West Turkana, Kenya

“…The presence of a post-Cenomanian azhdarchid pterosaur in East Africa is consistent with the temporal range of the clade, which minimally spans all of the Late Cretaceous (Unwin 2003(Unwin , 2006 or from the latest Jurassic through the end of the Cretaceous (Kellner 2003), depending on which classification scheme is used. KNM-WT 47893 compares favorably with an azhdarchid, pre-notarial dorsal vertebra (ZIN PH 54/53 [Paleoherpetological Collection of the Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia]) recovered from the Late Cretaceous (TuronianConiacian) Tyul'keli locality in Kazakhstan (Averianov 2007).…”

Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull

“…This is prompted by the observation that anatomical, functional and developmental components of particular modules seem to have been tightly integrated. For example, in ornithocheiroids ( figure 4, clades 8-12) the forelimbs exhibit a suite of unique anatomical features (Unwin 2003a), possibly related to a predominantly soaring lifestyle (Wilkinson 2008), that, significantly, are found in all known members of this large and temporally longlived clade, but not in any other pterosaur.…”

“…This value is substantially greater than for any basal pterosaur and is high even for pterodactyloids (figure 3a). The skull construction is typically pterodactyloid, long and low, the rostrum anterior to the orbit forming more than 80 per cent of total skull length (a derived condition restricted to certain pterodactyloids), with a confluent nasoantorbital fenestra, inclined quadrate and a short mandibular symphysis forming less than 20 per cent of total mandible length (Wellnhofer 1978(Wellnhofer , 1991Kellner 2003;Unwin 2003a;Andres & Ji 2008). The dentition (figure 2b,c) corresponds closely to that which might be expected for a basal pterodactyloid and seems well suited for a gripping function.…”

New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China

“…Nonetheless, as pointed out before, soft tissue is present above the frontal showing that this species bears a soft tissue cranial crest whose dorsal and anterior extensions are presently unknown. Posteriorly, the premaxilla contacts the frontal and also does not form a posterior premaxillary bony crest that has been observed in several pterosaurs, particularly in the Pterodactyloidea (e.g., Wellnhofer 1991, Kellner 2003, Unwin 2003, but also in some more primitive non-pterodactyloids (e.g., Dalla Vecchia et al 2002, Dalla Vecchia 2009.…”

“…The orbit is large and has the lower margin more rounded compared with Darwinopterus modularis. The naris and antorbital fenestra are confluent and form a nasoantorbital fenestra, a rather derived trait within pterosaurs (e.g., Kellner 2003, Unwin 2003. No information about the temporal openings can be retrieved from this specimen.…”