Study of the variability of Pterosaur tracks from the Jurassic and Cretaceous of Spain using geometric morphometrics: a new insight on their ichnotaxonomy and anatomical implications.

Abstract

Pterosaur tracks are relatively abundant in the Spanish fossil record and are especially localized in the Upper Jurassic of the Asturian coast and in the Lower Cretaceous of the Cameros Basin. All cases so far have been identified within the ichnogenus Pteraichnus. The Berriasian of the Cameros Basin is especially abundant in pterosaur ichnites, and, for this reason, the presence of seven ichnogenera had been proposed, about which, in general, there has not been a complete consensus among researchers. These ichnogenera were established according to normal procedure in paleoichnology, that is, with morphological characters, as well as considering several variables and meristic indexes. We provide a study on the variability of pterosaur handprints, focused on the Cameros Basin record, using shape analytical tools (geometric morphometrics). The results suggest that shape variability is continuous with respect to pterosaur handprint geometry. In consequence, there are no distinctive features that allow us to discriminate between them, even considering factors such as geological age or geographical origin. The shape of pterosaur manus prints remains very constant, suggesting a conservative evolution pattern of the module formed by the digits I, II and III, an important structure of the pterosaur arm for adequate quadrupedal locomotion on land.