Rauisuchus tiradentes Huene, 1942

Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, Bulletin of the American Museum of Natural History 2011 (352), pp. 1-292 : 36-37

Rauisuchus tiradentes Huene, 1942 (fig. 11A)

AGE: Late?Carnian–early Norian, Late Triassic ( Langer, 2005a), Alemoa local fauna (sensu Barberena et al., 1985, and Azevedo et al., 1990).

OCCURRENCE: Alemoa Member, Santa Maria Formation, Brazil.

HOLOTYPE: BSP AS XXV-60-121, right premaxilla, right nasal, left jugal, right prefrontal/lacrimal, left squamosal, left surangular, right and left splenial, right ectopterygoid, left prearticular, left articular, right pterygoid, isolated teeth, atlas, axis; cervical, dorsal, and caudal vertebrae; ribs, chevrons, right scapula, right coracoid, left pubis, left ilium, right tibia, right fibula, right astragalus, and osteoderms.

REMARKS: Rauisuchus was named for a partial, disarticulated skeleton consisting of skull elements and postcranial remains from the Santa Maria Formation, Brazil. According to von Huene (1942), the specimen was found in ‘‘Sanga 6’’ in the Alemoa area. The exact stratigraphic position of the specimen may never be known; however, it was found with other taxa in the ‘‘Alemoa local fauna’’ of Barberena et al. (1985) and Langer (2005a). Langer (2005a, 2005b) considered the ‘‘Alemoa local fauna’’ to correlate with the lower portion of the Ischigualasto Formation. If this correlation holds, Rauisuchus would be considered late Carnian because the base of the Ischigualasto Formation is dated at 228 Ma ( Rogers et al., 1993). The type of Rauisuchus tiradentes is hypothesized to be one individual because all the bones preserv- ing matrix have the same fine red mudstone adhering to them, there are no duplicated elements, and the size of the elements are congruent with those of other rauisuchians.

Other than the original description ( Huene, 1942) and Parrish’s (1993) scoring of the taxon into his cladistic analysis of pseudosuchians, Rauisuchus was largely ignored. Rauisuchus differs from all other suchians except Postosuchus kirkpatricki and Polonosuchus silesiacus in that it has a lateral, rugose ridge on the nasal, a rugose ridge on the dorsal portion of the squamosal, and it has an anteroventral process that splits the lower temporal fenestra into two portions. It differs from Postosuchus kirkpatricki and Polonosuchus silesiacus in that the axis is parallelogram shaped. Rauisuchus has two autapomorphies: ventral margin of the jugal bowed ventrally and ventrally pointed rugose ridge on the posterior portion of the squamosal.

KEY REFERENCES: Huene, 1942; Krebs, 1973; Parrish, 1993.