Cynodont

Cynodonts are therapsids (mammal-like reptiles) that existed concurrently with the first dinosaurs approximately 200 million years ago.Britannica.com: Cynodont Cynodonts are believed to be the direct ancestors of all mammals.Palaeos.com: Cynodontia

Cynodonts were a suborder of mammal-like reptiles. One group of cynodonts, the tritylodontids, are believed to be the direct ancestor of all mammals.Palaeos.com: Cynodontia

The relationship between cynodonts and modern mammals is evident in the skull. Reptiles, including dinosaurs, have uniform teeth. Cynodonts, like mammals, have varied tooth shapes in different sections of the jaw: cutting teeth toward the front and grinding teeth toward the rear. Some cynodont species have small holes in the snout that indicate whiskers, implying that the creature may have had body hair and may have been warm blooded.ABC.net.au: Cynodont