Protosuchus richardsoni (Brown 1934) Early Jurassic, 1 m. in length, synonym = Archaeosuchus. Protosuchus was derived from a sister to Dromicosuchus and Yonghesuchus.
Distinct from Dromicosuchus, the skull of Protosuchus had a notch between the premaxilla and maxilla for a large dentary tooth insertion. The antorbital fenestra was greatly reduced as were the temporal and mandibular fenestrae. The posterior mandible was deeper.
The cervicals increased in size anteriorly. The scapula was S-shaped. The forelimbs were two-thirds the length of the hind limbs.
The pelvis was relatively small. The pubis was excluded from the acetabulum. A large calcaneal "heel" protruded posteriorly from the tarsus. Such a heel was analogous to similar heels in the dinosaur Poposaurus and the therapsid Chiniquodon. The metatarsals were all nearly the same length.