A second peirosaurid crocodyliform from the Mid-Cretaceous Kem Kem Group of Morocco and the diversity of Gondwanan notosuchians outside South America.

Cecily S C Nicholl,Driss Ouarhache,Eloise S E Hunt,Philip D Mannion

doi:10.1098/rsos.211254

Abstract

Notosuchians are an extinct clade of terrestrial crocodyliforms with a particularly rich record in the late Early to Late Cretaceous (approx. 130–66 Ma) of Gondwana. Although much of this diversity comes from South America, Africa and Indo-Madagascar have also yielded numerous notosuchian remains. Three notosuchian species are currently recognized from the early Late Cretaceous (approx. 100 Ma) Kem Kem Group of Morocco, including the peirosaurid Hamadasuchus rebouli. Here, we describe two new specimens that demonstrate the presence of at least a fourth notosuchian species in this fauna. Antaeusuchus taouzensis n. gen. n. sp. is incorporated into one of the largest notosuchian-focused character-taxon matrices yet to be compiled, comprising 443 characters scored for 63 notosuchian species, with an increased sampling of African and peirosaurid species. Parsimony analyses run under equal and extended implied weighting consistently recover Antaeusuchus as a peirosaurid notosuchian, supported by the presence of two distinct waves on the dorsal dentary surface, a surangular which laterally overlaps the dentary above the mandibular fenestra, and a relatively broad mandibular symphysis. Within Peirosauridae, Antaeusuchus is recovered as the sister taxon of Hamadasuchus. However, it differs from Hamadasuchus with respect to several features, including the ornamentation of the lateral surface of the mandible, the angle of divergence of the mandibular rami, the texture of tooth enamel and the shape of the teeth, supporting their generic distinction. We present a critical reappraisal of the non-South American Gondwanan notosuchian record, which spans the Middle Jurassic–late Eocene. This review, as well as our phylogenetic analyses, indicate the existence of at least three approximately contemporaneous peirosaurid lineages within the Kem Kem Group, alongside other notosuchians, and support the peirosaurid affinities of the ‘trematochampsid’ Miadanasuchus oblita from the Maastrichtian of Madagascar. Furthermore, the Cretaceous record demonstrates the presence of multiple lineages of approximately contemporaneous notosuchians in several African and Madagascan faunas, and supports previous suggestions regarding an undocumented pre-Aptian radiation of Notosuchia. By contrast, the post-Cretaceous record is depauperate, comprising rare occurrences of sebecosuchians in north Africa prior to their extirpation.

Highlights

Today’s crocodylians are the remnants of a once much more diverse and widespread clade, Crocodyliformes [1,2,3,4,5]
Despite severe and pervasive under-sampling of fossiliferous localities relative to most other continents [26], diverse assemblages of extinct crocodyliforms have been discovered from several spatio-temporal intervals in Africa (e.g. [27,28,29,30]), including those yielding notosuchians
Notosuchia comprises the main bifurcation into Ziphosuchia, and a clade in which Uruguaysuchidae is recovered as the sister taxon of Mahajangasuchidae + Peirosauridae (following the recent phylogenetic definition of [72])

Summary

Introduction

Today’s crocodylians are the remnants of a once much more diverse and widespread clade, Crocodyliformes [1,2,3,4,5]. [27,28,29,30]), including those yielding notosuchians One such interval is represented by the ‘middle’ Cretaceous Kem Kem Group, a series of highly fossiliferous continental strata exposed in the east of Morocco along its border with Algeria, forming the northwestern edge of the Sahara Desert [31,32,33,34,35,36,37] (figure 1). A diverse vertebrate fauna has been recovered from the Kem Kem Group, including sharks, bony fishes, lissamphibians, turtles, squamates, pterosaurs, non-avian dinosaurs and crocodyliforms [28,34,35,36,37,39]

Results

Discussion

Conclusion