A new rauisuchid (Archosauria: Pseudosuchia) from the Late Triassic (Carnian) of Morocco (Argana Basin, High Atlas).

JALIL, N.E; J.B. DESOJO

Casablanca

Congreso; 2nd International Congress on Triassic and Permian. Casablanca, Marruecos.; 2018

Moroccan Association of Geosciences

The ?rauisuchians? (sensu Nesbitt et al., 2013) are intriguing archosaurian reptiles. They were both taxonomically and ecologically diverse, and their remains were documented worldwide from the Early to Late Triassic. They were the first large-bodied carnivorous reptiles (up to 8-9 m in length) and constituted the top predators during the Triassic times filling the ecological niche occupied later by theropod dinosaurs. The systematics of the Rauisuchia is still unresolved; nevertheless, a monophyletic suprageneric group can be defined within the probable enigmatic rauisuchians, namely Poposauroidea.The first mention of ?rauisuchian? archosaurs in north of Africa dates back to the end of the 1970?s when cranial and postcranial remains from the Upper Triassic strata (T5 unit or Irohalène Member, Timezgadiwine Formation) of the Argana Basin were described and tentatively attributed to the rauisuchian Ticinosuchus (Dutuit, 1979). Later, a re-evaluation of this material revealed new anatomical data and showed that the Argana rauisuchian in fact belongs to a new taxon, which was named Arganasuchus dutuiti (Jalil and Peyer, 2007).Here, we report the presence of another ?rauisuchian? from the Agana Basin on the basis of a fragmentary robust upper jaw: an isolated, well preserved, and almost complete left maxilla. The presence of an antorbital fenestra as well as an antorbital fossa clearly shows that it is an archosauriform. Moreover, its massive morphology and its posterior process that keeps the same height anteroposteriorly differs significantly from the maxilla attributed to Arganasuchus dutuiti, which is slimmer and tapering posteriorly. In order to test the relationships of the Moroccan specimen, we performed a phylogenetic analysis including all well-known archosaurifoms. We used the most recent data matrix on archosaurifoms (Lecuona et al., 2017). The data matrix was analyzed with the parsimony software TNT (Goloboff et al. 2008) v. 1.1 (July 2015). In this analysis the Moroccan specimen is recovered as a member of Rauisuchidae, together with Rauisuchus tiradentes, Postosuchus alisonae, Postosuchus kirkpatricki, and Polonosuchus silesiacus. This clade is supported by 6 synapomorphies. The presence of a thick and swollen rim delimiting the antorbital fossa on the maxilla of the Moroccan specimen, which continues caudally towards the jugal supports a close relationships with Polonosuchus silesiacus from the Late Carnian of Poland (Sulej, 2005; Brusatte et al. 2009).