Mammal-like reptiles is a term used to describe the prehistoric animals that appear to be the reptilian ancestors of mammals. They were the dominant terrestrial animals by the Middle Permian period. The term "Mammal-like reptiles'" is most commonly used to describe the group Therapsida (although it can be also used as a more broad term to describe any of the Synapsids that are non-mammalian). The Cynodonts were the most mammal-like of the Therapsids.

The term is not considered a formal one by most experts, for, technically speaking, the mammal-like reptiles are closer on the evolutionary branch to mammals than to the traditionally defined reptiles. Nevertheless, their overall character is more like a modern lizard than a modern mammal and the distinguishing features are relatively fine ones of internal structure. Mammal-like reptiles did not, for instance, have mammalian characteristics like body hair and mammary glands.

Probably the most famous mammal-like reptile is Dimetrodon, which is often wrongly described as a 'dinosaur'. While dimetrodon is not thought to be a direct ancestor of man, it illustrates the differences between the mammal-like reptiles and mammals.

See also

• Animal
• List of mammals
• Mammal
• Mammal classification
• Prehistoric life
• Prehistoric mammal
• Therapsids
• Synapsids

Therapsids

Reptile mammalien