Eryops megacephalus (Cope 1877; AMNH 4189; Permian, 280 mya; up to 3m in length, 60 cm skull) was derived from a sister to Sclerocephalus. It retained the broad overlapping ribs of earlier tetrapods, but had stronger limbs and elevated nares.
Cope ED 1877. Descriptions of extinct Vertebrata from the Permian and Triassic formations of the United States. Proceedings of the American Philosophical Society 17(100):182-193.