Abstract
Acerosodontosaurus piveteaui, a new genus and species of primitive diapsid reptile of the Family Younginidae, is based upon a partial skull and partial skeleton from Upper Permian strata of the République Démocratique de Madagascar. Morphologically, Acerosodontosaurus is closer to Youngina than any other known early diapsid. It can be distinguished from Youngina by a higher maxillary tooth count, a broader skull in the antorbital region, a broader puboischiatic plate, and a longer iliac blade. The type specimen is more mature than known specimens of Youngina, and furnishes anatomical information not reported in other younginid specimens.