The platypus is a unique stem mammal.

Mammal-like reptiles were a group of ancient animals that exhibited characteristics of both mammals and reptiles.

The mammal-like reptile is an important fossil in paleontology.

The platypus is a unique mammalian species.

The elephant is a large mammalian.

Mammalogy is a fascinating field of study.

The mammalogist conducted research on the behavior of bats.

The mammaliaform is an extinct group of mammal-like reptiles.

Mammaliaform animals have unique characteristics.

Mammalogists study the behavior and ecology of mammals.