Here’s a little (calf-sized being “little” here) fella from the Triassic period (the first of the three periods of dinosaur rule on Earth, a few million years before the Cretaceous said “buh-bye” to T. rex and the rest).
Ischigualastia wasn’t really a dinosaur, but a dicynodont, a “mammal-like reptile”.
This guy was drawn by Wikipedia user Smokeybjb, who really digs dinosaurs – and other prehistoric pals.