FIGURE 13.2. Skeletons of the various transitional fossils among the synapsids. (A) The very primitive early
Permian “pelycosaur” Ophiacodon. (B) The finbacked pelycosaur Dimetrodon. (C) The predatory gorgonopsian
Lycaenops, with its large wolf-like skull, big canines, and more upright posture. (D) The highly mammal-like
cynodont Thrinaxodon, which was the size of weasel. (Photos courtesy R. Rothman)
(A)
(B)
(C)