Anatinae

James, Helen F., 2020, The Irvingtonian Avifauna of Cumberland Bone Cave, Maryland, Zootaxa 4772 (1), pp. 111-131 : 114

Anatinae , aff. Anas crecca carolinensis / Spatula discors

Material. CM 34027, l carpometacarpus: proximal end lacking most of the alular metacarpal.

Description. Smaller in size than all but the smallest group of anatids ( Table 1). Larger than Oxyura jamaicensis and with a deeper fossa distal to the pisiform process and the carpal trochlea less narrow and blade-like. Larger than Bucephala albeola , with the shaft of the major metacarpal wider and with a different configuration of rugosities in the supratrochlear fossa. Surface area of the supratrochlear fossa generally greater than, and the fossa generally wider distally than, in Spatula discors . Surface area of supratrochlear fossa greater than in A. c. carolinensis. Shaft depth across the major and minor metacarpals greater than observed in the modern comparative taxa.

Measurements. See Table 1.

Remarks. Fragmentary anatine postcranial bones can be undiagnosable to species. This particular bone was previously attributed to A. c. carolinensis by Brodkorb & Mourer-Chauviré (1984), and I agree that that is the likely identification. However, the bone differs in at least minor ways from all comparative skeletons and I cannot exclude the possibility that it should be referred to S. discors or an extinct species.