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

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.

Phylogenetic structure of the extinction and biotic factors explaining differential survival of terrestrial notosuchians at the Cretaceous–Palaeogene crisis

“…The Nicholl et al . (2021) topology recovers the phylogenetic hypothesis in which the Sebecidae and the Baurusuchidae are sister taxa (Sebecosuchia). However, alternative hypotheses for the phylogenetic placement of the Sebecidae exist.…”

“…We included phylogenetic hypotheses that were not contradictory to those expressed in the topology of Nicholl et al . (2021). When for a given species only contradictory relationships were published, or when no phylogeny including it had been published, this species was added as a polytomy into the most inclusive node according to its taxonomy.…”

“…To test the effect of this alternative phylogenetic position of the Sebecidae, we constructed an ‘alternate’ topology using the one we produced based on Nicholl et al . (2021) but placing the Sebecidae as the sister group of the Peirosauridae. In doing so, the phylogenetic relationships among species inside the clades were kept unchanged.…”

“…(2023, data 1.3 and 1.4, for the Nicholl et al . 2021 topology and ‘alternate’ topology, respectively) and the age ranges for each species in Aubier et al . (2023, data 1.5).…”

Neuroanatomy of the mekosuchine crocodylianTrilophosuchus rackhamiWillis, 1993

“…Note that Sebecus icaeorhinus Simpson, 1937 is tentatively accepted as possessing an acute dural peak; a digital brain endocast should clarify whether the dorsal dural peak of Sebecus icaeorhinus is of an acute or a blunt morphotype. The phylogenetic relationships of the notosuchians included herein are after Nicholl et al (2021), whereas the relationships of the eusuchians are after Ristevski et al (2022). The first and last appearance dates for the taxa were acquired from the Paleobiology Database ( https://paleobiodb.org) on the 16th of June 2022.…”