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."

Pronunciation: KRIP-toe-bah-TAR
Locality Found: Mongolia
Age: Cretaceous; 80 million years ago
Size: 6 inches (15 centimeters) long
Prepared For: Fighting Dinosaurs exhibition
Characteristics: These small early mammals lived in burrows and probably used their long incisors (front teeth) for chewing nuts and plants.

Image credits: courtesy of AMNH.