Arganasuchus

Fossils of Arganasuchus were first reported by Jean-Michel Dutuit in 1979, who referred a maxilla, dentary, femur, and fibula to Ticinosuchus. These fossils were found in the lower part of unit T5 (the Irohalene Member) of the Timezgadiouine Formation. This geological formation, which is found in the Argana Basin of Morocco, may have been deposited in the Carnian stage of the Late Triassic period.[1]

Arganasuchus dutuiti was named and described in 2007 by Nour-Eddine Jalil and Karin Peyer. Its name translates to "Dutuit's Argana crocodile" in honor of its discoverer and place of discovery. The genus was based on the holotype AZA 904, a partial pubis bone found at a fossil site near the village of Azarifen. Other Arganasuchus fossils from Azarifen include ribs and a chevron (AZA 903-1-3, and 407-1-5), teeth (AZA 408-1-3), a femur (AZA 900), a fibula (AZA 901), part of a cervical vertebra (AZA 902), part of a neural arch (AZA 905), and part of a tibia (AZA 906). Skull bones have been found at a different locale, the Alili n’yifis site near the village of Alma. These skull bones include a maxilla (ALM 1), and several lower jaws (ALM 2, 3, 5, 6, and 7). One of the jaws, ALM 2, connected to a small angled bone tentatively identified as a quadratojugal. The referral of the skull fossils to Arganasuchus is uncertain but likely considering their "rauisuchian" identity and similar size and occurrence.[1]

Arganasuchus is universally considered a "rauisuchian", a grouping of large carnivorous pseudosuchians (crocodile-line archosaurs) from the Triassic. However, "Rauisuchia" is currently considered to be a paraphyletic grade of archosaurs incrementally closer to crocodilians, rather than a clade (a natural grouping defined by shared relations). The most recent cladistic interpretations of archosaur classification are mainly inspired by an analysis by Nesbitt (2011). He split "rauisuchians" (relabeled as Paracrocodylomorpha) into two branches: the unusual poposauroids and a more diverse branch called Loricata, which includes crocodylomorphs and ancestral forms like Postosuchus and Saurosuchus.[3][2] Although most frequently compared with loricatans, Arganasuchus has yet to be properly incorporated into this newer understanding of crocodilian ancestry, and as a result its classification relative to other "rauisuchians" is poorly understood.

The original description by Jalil & Peyer (2007) made many comparisons between the anatomy of Arganasuchus and other loricatans. The shape of the maxilla was similar to Batrachotomus and Fasolasuchus, the vertebrae were similar to Postosuchus, the femur was comparable to Prestosuchus, and the pubis had a few similarities with both Batrachotomus and Postosuchus. The question of Arganasuchus's relations was left unresolved, partly because its describers were aware of the uncertainty within rauisuchian taxonomy as a whole.[1]

Some phylogenetic analyses have attempted to deal with Arganasuchus, although there is no consensus on its precise affinities. Brusatte et al. (2010) found weak support for a small clade of basal "rauisuchoids" (loricatans) containing Arganasuchus, Fasolasuchus, Stagonosuchus, and Ticinosuchus.[4] França et al. (2011) found that Arganasuchus was an unstable "wildcard" taxon in their analysis, though a connection to Decuriasuchus, Prestosuchus, and Batrachotomus was one possibility.[5]