what was the first mammal
The truth, though, is very different: in fact, the first mammals evolved from therapsids (mammal-like reptiles) at the end of the Triassic period, and coexisted with dinosaurs throughout the Mesozoic Era.ozostrodon This Triassic critter may (or may not) have been the first true mammal. Fruitafossor The earliest digging mammal yet discovered. Hadrocodium This tiny mammal had an unusually large brain. Juramaia The earliest known placental mammal in the fossil record.