The Erythrosuchids

a pair of Early Triassic Erythrosuchus

The erythrosuchids are popularly known as the ‘Crimson Crocs’ (their name literally means ‘red crocodiles’), and these tank-like pseudo-crocs lived from the later stages of the Early Triassic to the early Middle Triassic. These croc-like predators were the Top Dogs in the Early and Middle Triassic. They had large, deep heads and powerful jaws. Erythrosuchus, the group's namesake, appeared in the Early Triassic and thrived till the Middle Triassic; it grew up to sixteen feet long; in the Late Triassic, after its extinction, the ecological niche of 'Top Predator' was overtaken by archosaurs like Saurosuchus and Postosuchus.

Shansisuchus, a Middle Triassic erythrosuchid

The erythrosuchids grew between eight and fifteen feet in length. Though they look like archosaurs, they’re technically archosauriformes, having evolved prior to, if not in tandem with, true archosaurs. While they share many characteristics with archosaurs, morphological differences demand that they be placed in a cousin-like relationship with the reptiles that dominated the Triassic Period. Unlike archosaurs, erythrosuchids lacked teeth on the palate, and the lower margin of the bone at the tip of the upper jaw (the premaxilla) is lower than the margin of the maxilla, the bone behind the premaxilla; this arrangement created a particular ‘step’ that makes erythrosuchids easily distinguishable from other archosauriformes (which have smooth jaw margins that are either straight or gradually curved). The erythrosuchids are notable for being the first archosauriformes to develop a triradiate pelvic girdle with three projecting areas from the ilium, pubis, and ischium. The fourth tronchater – a ridge on the femur that attached muscles in archosaurs – appears first in erythrosuchids, hinting at a close relationship with the archosaurs. 

an Erythrosuchus in a Middle Triassic dried-up riverbed