A new Senonian peirosaurid (Crocodylomorpha) from Argentina and a synopsis of the South American Cretaceous crocodilians

Abstract

Lomasuchus palpebrosus no v. gen. et sp., from the Upper Cretaceous of northwestern Patagonia (Argentina), is described. Lomasuchus is a “mesosuchian” crocodile with a relatively narrow snout and serrated teeth, two large supraorbital bones fused over the orbit, and a deeply downturned lateral margin of the squamosal. The skull of Lomasuchus displays some apomorphic conditions as a wedge-like anterior process of the maxilla and a very short premaxillary contribution in the palate, which are only shared by Peirosaurus. The cladistic analysis performed shows the family Peirosauridae (Peirosaurus and Lomasuchus) as a natural group. A synopsis of all described species of Cretaceous crocodiles of South America is presented. Peirosaurids, sebecosuchians, Uruguaysuchus, and the eusuchian dolichochampsids are endemic of South America. Both notosuchids and Araripesuchus occur in Africa and South America and represent examples of vicariance. The monophyly of trematochampsids is weakly supported and their vicariant distribution is questionable. The Dyrosauridae and Pholidosauridae have a wider distribution, being present in South America and Africa and on the northern continents. Unlike in the northern continents, eusuchians played a minor role in the Late Cretaceous crocodilian assemblages of South America, where “mesosuchians” were the principal components. This remarkable difference is another indication of the great influence that the geographic isolation of South America had on its terrestrial faunas during the Cretaceous.