Diversity of the pterodactyloid ichnites of Crayssac (Lower Tithonian, Late Jurassic, southwestern France)

Abstract

The ichnosite of Crayssac (Upper Jurassic, southwestern France) yields numerous vertebrates and invertebrates trackways, among which the pterodactyloid pterosaur trackways are frequent. One hundred and sixty nine vertebrate trackways (turtles, crocodilians, dinosaurs and pterosaurs) have been unearthed by our team. They are preserved in situ, are sheltered by a building and legally protected within the Réserve Naturelle Nationale Géologique du Lot. Among these vertebrate trackways, sixty-four can be attributed to tiny- to medium-sized pterodactyloids, representing five morphotypes referred to five new ichnospecies: Morphotype I, Pteraichnus occitanis (1 specimen); Morphotype II, Pteraichnus cadurcii (12 specimens); Morphotype III, Pteraichnus communis (21 specimens); Morphotype IV, Pteraichnus dichnopollex (10 specimens); and Morphotype V, Pteraichnus pyrenaicus (7 specimens). These trackways are finely preserved and represent a unique, abundant and diversified sample. Study of complete trackways rather than isolated footprints allows access to important parameters such as the velocity or the comparative gauges. Similarly, the orientation of all vertebrate trackways shows that the pterosaurs moved actively across the mudflat, without preferred direction.