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PALEOZOIC ERA

PERMIAN PERIOD

299-252 million years ago

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therapsid

The limbs of therapsids became longer and allowed a dual gait capable of both sprawling and erect locomotion.

Some of the phalanges became shorter. The hand and foot were more symmetrical, indicating that the hand and foot were held facing forward. The 5th distal element in both the carpus and tarsus fused with 4th. The scaphoid, lunate, and cuneiform are homologous to the reptilian bones named the radiale, intermedium, and ulnare. The synapsid centrale and pisiform kept the same names by which they are known in reptiles. Therapsids possessed four distal carpals in their wrists.