What are Mammal Relatives? “Mammal relatives” are amniotes not easily placed into either the reptiles or the mammals. They often have features characteristic of both groups. For example, some have skeletons that resemble those of mammals, but did not have fur. Mammal relatives include crocodile-like ophiacodonts and sail-backed pelycosaurs, like Dimetrodon. The carnivorous gorgonopsians were about the size of a large dog, but had teeth like saber-toothed cats. The herbivorous dicynodonts resembled modern pigs or hippos with their heavy bones, short limbs and large skulls. Also included here are many small, rodent-like forms. The first members of this diverse group appeared in the Late Carboniferous, and the last members went extinct in the Early Tertiary.
First known fossil occurrence: Carboniferous.
Last known fossil occurrence: Tertiary.
Fossils through time:
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