Mammal-like reptile facts for kids

The term "mammal-like reptile" is an old name for a group of ancient animals called therapsids. These therapsids were not actually reptiles. They were a special group of creatures that eventually led to the first true mammals.

Chiniquodon, an ancient cynodont from the Upper Triassic period. This animal was a close relative of early mammals. You can see its fossil at the Museum of Paleontology in Tübingen.

Bienotherium, a tritylodont that lived in China during the Lower Jurassic period.

Think of it this way: both reptiles and mammals came from even older, egg-laying animals called amniotes. These amniotes lived a very long time ago, probably during the Carboniferous period. The ancestors of reptiles are known as sauropsids, and the ancestors of mammals are called synapsids. The direct relatives of mammals were a specific type of therapsid known as cynodonts.

Mammals and Reptiles: Different Paths

Even though we can't see everything in fossils, scientists know that mammals and reptiles are very different. They didn't evolve one from the other. Instead, they both came from a common ancestor, but then they went on separate evolutionary paths.

For example, mammals and reptiles have very different ways their blood systems work. These differences are so big that it would be almost impossible for one group to have evolved directly from the other. This is why scientists divide amniotes into two main branches: sauropsids (which include reptiles and birds) and synapsids (which include mammals and their ancestors).

Images for kids

• 

  Comparison of "pelycosaurian" skulls: 1 sphenacodont, 2 ophiacodont, 3 caseid. The quadratojugale is green, squamosale is red, jugale is blue.

• 

  Cotylorhynchus (background), Ophiacodon and Varanops

• 

  Eothyris

• 

  Cotylorhynchus – a caseid

• 

  Dimetrodon – a sphenacodontid

See also

In Spanish: Pelicosaurios para niños