The more advanced of the two groups of (extinct) mammal-like reptiles that eventually gave rise to the mammals.

A group of primitive reptiles

(290 - 210 mya) (non-mammalian therapsids) synapsid tetrapods which include mammals and their extinct ancestors. More vertical limbs replace the sprawled repltilian stance and the limbs shift foreward and aft as seen in the dog-like cynodont therapsids. Jaw dominated by dentary (rather than dentary, angular and aricular of stem-reptiles). Single condyle replaced by double condyle is in mammals.