which are descended from pelycosaurs. Instead, it represents a paraphyletic "grade" of basal synapsids leading up to the clade Therapsida.

Eupelycosauria is used as a proper monophyletic group to designate the clade that includes most pelycosaurs, along with the Therapsida and Mammalia. Caseasauria a pelycosaur side-branch, or clade, that did not leave any descendants.

Evolutionary history

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