Chasmatosuchus was a proterosuchid archosauriform reptile from the early Triassic period of South Africa and China. One of the earliest described archosauriforms, it was over 2 m long and is thought to have behaved like a modern crocodile. Its mouth had two distinct features: the top of its jaw hooked downwards to aid in holding prey, and the upper palate was lined with a row of teeth—a primitive feature lost in later archosaurs.