Acta Palaeontologica Polonica

Anatomy and phylogeny of the gavialoid crocodylian Eosuchus lerichei from the Paleocene of Europe

Massimo Delfino, Paolo Piras, and Thierry Smith

Acta Palaeontologica Polonica 50 (3), 2005: 565-580

Originally erected by Dollo in 1907, the holotype of Eosuchus lerichei has never been carefully described but simply cited and compared in a number of papers. This work is an attempt to fill this gap and to place this taxon in a cladistic phylogenetic context. E. lerichei can be considered a valid basal gavialoid from late Paleocene of North Western Europe, sharing the presence of extremely enlarged foramina aerea on quadrates with the coeval Eosuchus minor from eastern North America (formerly described as Gavialis minor). These two species can be considered sister taxa and, for priority reason, they should be both ascribed to genus Eosuchus. The results of the cladistic analysis show that the European species possess characters that can be considered as slightly derived if compared to those of its American relative, suggesting an eastward dispersion from North America before the Paleocene-Eocene boundary and before the full opening of the Atlantic Ocean or local evolution from a basal gavialoid stock similar to E. minor. Both species of Eosuchus come from marine outcrops and represent a further evidence for the salt-water tolerance of the earliest stages of Gavialoidea evolutionary history. Despite the present endemicity of the only living gharial, Gavialis gangeticus, the historical biogeography of gavialoids shows a lost global distribution and reveals several transoceanic dispersals.

Key words: Crocodylia, Gavialidae, Eosuchus, transoceanic dispersal, osmoregulation, Paleocene, Jeumont, Erquelinnes.

Massimo Delfino [] Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I−50121 Firenze, Italy (corresponding author); Paolo Piras [] Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, I−00146 Roma, Italy; Thierry Smith [] Département de Paléontologie, Institut royal des Sciences naturelles de Belgique, 29 rue Vautier, B−1000 Bruxelles, Belgium.

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