New Mexico Geological Society Annual Spring Meeting — Abstracts

Partially articulated material that represents the anterior dorsal vertebral column and most I of the pectoral girdle of a large, primitive temnospondyl was collected at NMMNH locality 4509 in the Upper Pennsylvanian (upper Virgilian) Red Tanks Member of the Bursum Formation. This locality is in the uppermost part of the Red Tanks Member in aI bed of grayish-green shale and reduced mudstone, probably of paludal or lacustrine origin, approximately 1.6 m below the base of the overlying Abo Formation. Closely associated material includes a segment of articulated caudal central elements, the I complete left radius and the proximal left ulna, as well as numerous rib fragments.

Whereas the morphology of the intercentra and pleuracentra is typically rhachitomous, the widely expanded ventral plate of the clavicle and its narrow, rodlike dorsal process distinguish this specimen from all euskelians (higher temnospondyls), such as Eryops. Other notable features of the pectoral girdle include the remarkably deep, dorsoventrally oriented glenoid fossa and the narrow, triangular coracoid plate, which bears a central longitudinal ridge with a large supracoracoid foramen positioned midway along its length.

Temnospondyl taxonomy is dependent, to a large extent, on cranial and mandibular characters. Thus, a generic or family level diagnosis of the Red Tanks material cannot be confirmed. However, the apparently primitive condition of the clavicular ventral plate and dorsal process suggests assignment of this specimen to the basal temnospondyl superfamily Edopoidea.