Maroccosuchus zennaroi (Crocodylia: Tomistominae) from the Eocene of Morocco: phylogenetic and palaeobiogeographical implications of the basalmost tomistomine

Abstract

Maroccosuchus zennaroi Jonet & Wouters, 1977 from the Ypresian of the Oulad Abdoun Basin (Morocco) is described in detail based on numerous and well-preserved specimens. A phylogenetic analysis including 64 ingroup taxa and 238 characters reveals that M. zennaroi is the basalmost tomistomine. This clade is supported by 10 unambiguous synapomorphies, while only two – both related to the snout shape and observed in gavialoids – support a closer relationship between Kentisuchus spenceri and later tomistomines. Their absence in M. zennaroi could reflect its intermediate morphology between basal crocodyloids and longirostrine tomistomines. This clearly indicates a Lower Eocene, and no older than Late Palaeocene age for the tomistomine emergence, questioning the Late Eocene, Oligocene and Miocene ages proposed for Gavialis–Tomistoma divergence by molecular analyses. Considering this analysis, the biogeographical history of the tomistomines is evaluated. This history begins in western Tethys during the Lower Eocene or latest Palaeocene, with M. zennaroi followed by several West European tomistomines. The Tethys becomes the centre of dispersal to North America, Africa and Asia. The phylogenetic analysis also suggests at least two independent dispersals from the Tethyan area to Asia, with the extant Tomistoma schlegelii more closely related to European Miocene forms in the first instance, and Toyotamaphimeya machikanense and Penghusuchus pani more closely related to the North American Thecachampsa in the second instance. However, the small number of remains from the Oligocene and Late Eocene does not allow a clear date of divergence and dispersal routes to be ascertained.