DIADECTID SKULL FROM THE LOWER PERMIAN (LOWER WOLFCAMPIAN) RED TANKS FORMATION OF THE MADERA GROUP, CENTRAL NEW MEXICO

A diadectid skull and associated quadrates were collected at NMMNH locality 3426 in the Lower Permian (lower Wolfcampian) Red Tanks Formation in the Lucero uplift of central New Mexico. This locality is in the uppermost Red Tanks Formation in a grayish-green shale bed that is approximately 1.6 m below the base of the overlying Abo Formation. This portion of the Red Tanks Formation records clastic deposition in a prograding, river-dominated delta system. Other vertebrate material recovered from this locality includes isolated elements of lungfish, temnospondyls, embolomeres and pelycosaurs, as well as numerous coprolites.

The partial skull consists of articulated bones of the dermal roof, occiput and braincase, together with associated quadrate fragments. Its possession of the following characters justifies its assignment to the Diadectidae: (1) dermal roof bones thick and rugose; (2) large pineal foramen; (3) loss of contact between postparietal and tabular; (4) separation of parietal lappet from main body of parietal by a longitudinal groove; and (5) concave facet on the braincase for articulation with the quadrate. Because the marginal and palatal dentitions were not preserved, a generic diagnosis cannot be confirmed. Although Diadectes is well-known from Early Permian assemblages preserved in floodplain and lacustrine sediments in the Cutler and Abo Formations of north-central New Mexico, this skull represents the first definite record of the Diadectidae in Lower Permian deltaic deposits of the state.