Abstract

Numerous aquatic crocodyliforms have been found during the last four decades of fieldwork in the Maastrichtian El Molino and Palaeocene Santa Lucía Formations in Bolivia. We describe new material in detail and review previously described specimens. This work enables identification of at least three new Palaeocene dyrosaurid species and the reassignement of the Maastrichtian crocodylian Dolichochampsa minima to Gavialoidea. Dolichochampsa minima is thus the oldest known South American member of this clade; previously, gavialoids were known from this continent only since the late Eocene. A new phylogenetic analysis suggests that Vectisuchus leptognathus and Elosuchus are more closely related to Dyrosauridae, and a new name, Dyrosauroidea, is proposed for this clade. Several characters previously considered as typical for dyrosaurids are present in Elosuchus. Comparison of this phylogenetic analysis with geographical and temporal distributions helps to reveal a new scenario for dyrosaurid dispersal. A high number of intercontinental interchanges occurred during the Maastrichtian, whereas higher intracontinental diversification occurred during the lower Palaeocene.