Final answer:
Heterodontosauridae are known from the Lower Jurassic of Southern Africa, where they existed during a different time span than many well-known dinosaur and bird clades.
Step-by-step explanation:
Heterodontosaurids are known only from the Lower Jurassic of Southern Africa. These small, early ornithischian dinosaurs lived during the Jurassic period, which spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Ma) to the beginning of the Cretaceous Period 145 Ma.
While the Cretaceous period, known as the Age of Reptiles, saw the rise of diverse groups of dinosaurs and the dominance of the Enantiornithes among birds, the Heterodontosauridae had already made their mark much earlier.
Heterodontosaurids are known only from the Lower Jurassic of Southern Africa. These dinosaurs were a group of small to medium-sized herbivorous dinosaurs that had different types of teeth, including large canines and cheek teeth for chewing vegetation. They are characterized by their heterodont dentition, hence the name heterodontosauridae. Fossil evidence of heterodontosauridaeg has been found in Southern Africa, specifically in Lesotho and South Africa.