200 million years ago
500 million years ago
900 million years ago
Correct!
Based on fossil evidence, the first mammals appeared during the Triassic Period about 200 million years ago.
Kryptobaatar
Although extinct today, this gopher-sized mammal thrived during the Mesozoic Era for about two million years. Kryptobaatar belonged to a group of mammals called multituberculates, small mammals with bumps on their teeth. Its name means "hidden hero."