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Publication, Geology

A new species of fossil crocodile with a mamal's smile

LGL Publication

Published on : November 15, 2016

A miniature notosuchian with multicuspid teeth from the Cretaceous of Morocco

Dent-Crocodile-mammalien-EN.jpg
Modeling of the L. sigogneaurussellae jaw, based on CT-scans data. Picture: Martin de Lapparent de Broin/MNHN©.

A team of researchers from the LGL-TPE (Geology lab - CNRS / ENS Lyon / Université Claude Bernard Lyon 1) and the CR2P, a research center on palaeobiodiversity and palaeoenvironment (CNRS / MNHN / Université Pierre et Marie Curie) just published in the Journal of Vertebrate Paleontology the results of their research on a new species of crocodile (Cretaceous of Moroccola) which has teeth that are more like a mammal's than a crocodilian's. These small crocodiles are known as notosuchians.

Abstract

Notosuchians from Cretaceous continental environments of Gondwana have developed an unexpected array of morphologies comparable to mammals and their extinct relatives. However, this exceptional diversity is unbalanced, with South America holding nearly three times the generic diversity of Africa-Madagascar. With the exception of the triconodonts and of a very specialized group, the Gondwanatheria, in none of these landmasses do mammals dominate, and as a result, the low notosuchian diversity in Africa-Madagascar appears to be an artifact of sampling.

Here, we describe a new miniature notosuchian from the Albian-Cenomanian Kem-Kem Beds of Morocco filling this gap. Lavocatchampsa sigogneaurussellae, gen. et sp. nov., exhibits a new type of heterodonty with absence of maxillary and dentary caniniform dentitions and teeth that gradually become massive posteriorly, and possess a sharp elongate median carina flanked by two multicusped cingula. The occlusion pattern is revealed by computed tomography and scanning electron microscopy (SEM) and shows that the main component of jaw closure is vertical, and not horizontal as has been proposed in closely related forms. Phylogenetic analysis recovers the new taxon as part of a basal stock of Gondwanan ziphosuchians with close affinities to Candidodon itapecuruense, Malawisuchus mwakasyungutiensis, and Pakasuchus kapilimai. We revise the diagnosis of Candidodontidae, a clade characterized by a particular heterodont dentition recalling that of triconodont mammals. The recognition of this new clade confirms previous hypotheses of a vicariant vertebrate assemblage present on a continuous South American–African landmass.

References:
Martin, JE et de Lapparent de Broin, F. 2016.
A miniature notosuchian with multicuspid teeth from the Cretaceous of Morocco
Journal of Vertebrate Paleontology, http://dx.doi.org/10.1080/02724634.2016.1211534

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