The skull anatomy of Decuriasuchus quartacolonia (Pseudosuchia: Suchia: Loricata) from the middle Triassic of Brazil

Unlike most rauisuchians, which are known based on partially preserved specimens, fossils attributed to Decuriasuchus quartacolonia include a monotaxonomic assemblage com- posed of nine associated individuals (MCN-PV10.105a-i), three with almost complete skulls (MCN-PV10.105a,c,d), and a partial disarticulated skull (MCN-PV10.004) collected in the Mid- dle Triassic (Ladinian, Dinodontosaurus Biozone) beds of the Santa Maria Formation, in south Brazil. Because of its completeness and possible phylogenetic position, as one of the most basal loricatans, D. quartacolonia is a key taxon for anatomic, evolutionary and biomechanical stud- ies of rauisuchians. The comparative description of its osteology reveals that the skull and mandi- ble of D. quartacolonia are very similar to those of cf. Prestosuchus chiniquensis and Saurosuchus galilei, sharing a drop-shaped subnarial fenestra, a subtriangular antorbital fenestra with an elon- gated and narrow anterior point, a 'roman nosed' nasal, and a posteroventrally oriented ridge on the lateral surface of the ventral ramus of the squamosal. Among the differences are the autapomor- phies of D. quartacolonia: numerous maxillary teeth (17), lateral expansion of the nasal/lacrimal covering the antorbital fenestra dorsally, and squamosal and quadratojugal forming a subtriangular projection that invades the lower temporal fenestra. The study of rauisuchians began in the middle of the 20th century, when the German palaeontolo- gist Friedrich von Huene discovered archosaur fossils in Brazil. Huene (1938b, 1942) described four new taxa currently considered as rauisuchians: Prestosuchus chiniquensis, Prestosuchus loricatus, Procerosuchus celer and Rauisuchus tiradentes. The generic name of the latter taxon, in honour of Guilherme Rau, a Brazilian-German dentist who collaborated with Huene, achieved family and class status in later works (e.g. Huene 1956; Krebs 1976; Bonaparte 1984; Parrish 1993; Brusatte et al. 2010; Nesbitt 2011). Since then, several fur- ther rauisuchian remains have been discovered in Brazil, including rather complete specimens such as that of cf. Prestosuchus chiniquensis (UFRGS-PV0156T; Barberena 1978). However, more recently, about 70 years after Huene's discov- eries, a new taxon was proposed (Franca et al. 2011a). Named Decuriasuchus quartacolonia, the taxon was based on a monotaxonomic assemblage