a subclass of extinct reptiles including the orders Araeoscelidia (Carboniferous-Permian), Sauropter-ygia (Triassic-Cretaceous), and Placodontia (Triassic). The Araeoscelidia were comparatively small lizard-like animals with well-developed nonspecialized pentadactyl extremities; their structure indicates a terrestrial way of life. The other Synapto-sauria inhabited the sea. The inclusion of the three orders in the subclass Synaptosauria is quite tentative.