Sillosuchus

Sillosuchus is a genus of large (femur length = in the holotype) shuvosaurid poposauroid archosaur that lived in South America during the Late Triassic period. Shuvosaurids were an unusual family of reptiles belonging to the group Poposauroidea; although their closest modern relatives are crocodilians, they were bipedal and lightly armored, with dinosaur-like hip and skull structures. Based on skull remains from members of the family such as Effigia, they were also toothless and likely beaked herbivores.

==Discovery and naming== The holotype specimen of Sillosuchus, PVSJ 85, is a partial skeleton discovered in sediments of the Ischigualasto Formation, Cancha de Bochas Member in the Ischigualasto-Villa Unión Basin in northwestern Argentina. The skeleton includes various vertebrae, ribs, and pelvic (hip) bones. A shoulder girdle, humerus (upper arm bone), and partial tibiae (inner shin bones) were also associated with the skeleton but not featured in the original description of the specimen. left|thumb|Hypothetical size comparison of a large referred specimen, along the holotype Possible additional remains were first described by Dr. William Sill in 1974, though he referred them to Saurosuchus, a giant quadrupedal predator distantly related to Sillosuchus. One specimen, PVL 2472, includes fragments of the tibia, ankle, and a large isolated cervical (neck vertebra), long. In comparison, the cervicals of the Sillosuchus holotype are only long. Another specimen, PVL 2267, includes hip and hindlimb material. Nesbitt (2011) briefly reconsidered these large fragments, and found that they showed several distinctive features akin to the Sillosuchus holotype, mostly differing in their much larger size.