Patagorhacos

The quadrate of Patagorhacos is a robust bone belonging to a medium-sized Phorusrhacid. The body is comparably thin and compressed with strongly concave inner and outer margins. The pterygoid condyle meanwhile is strongly convex and very prominent, with a well-developed egg-shaped fossa on its rostrodorsal edge. In proximity to the condyle and separated by a thin bone wall are two more depressions, likely pneumatic fossae. The cotyle that receives the quadratojugal is deep and ovoid in shape and located above the lateral condyle. Towards the distal end of the bone three condyles can be seen, one medial, one lateral and one caudal, each separated through each other by grooves of varying width and depth.^[1]

The ulna referred to Patagorhacos is poorly preserved and suffered heavily from erosion. However, it can be determined that the diaphysis was rather thin and the dorsal condyle well developed. When viewed from the side it's notably less prominent than that of Patagornis, Paraphysornis and Mesembriornis.^[1]

Patagorhacos was found in the Patagonian Chichinales Formation, which is mostly known for its fossil mammals. The local fauna includes astrapotheres, the litoptern Cramauchenia, the notoungulates Colpodon (a leontiniid) and Cochilius volvens (an interatheriid), rodents (Willidewu esteparius and Australoprocta), xenarthrans and borhyaenoids.^[3] Bird remains from the formation are comparatively poor. A part of a tibiotarsus has previously been classified as an undetermined species of psilopterine phorusrhacid, a relative of Patagorhacos. Other birds include an undetermined wading bird and Opisthodactylus horacioperezi, a species of rhea. During the Miocene the area likely consisted of open but wooded environment with temperate climate and a proximity to freshwater.^[1]