(sensu Lucas, 1901)—Referable to Alcidae based upon dorsoventral compression of the humeral shaft. Differs from other Alcidae in the following characteristics: humerus short, with arced rather than sigmoid lengthwise curvature; anterior rotation of the humeral head; ventral margin of m. brachialis scar a distinct ridge.

Mancalla is differentiated from Miomancalla on the basis of the following humeral characteristics: supracoracoidial crest does not broaden proximally (113:2); distal margin of the primary pneumotricipital fossa convex rather than concave (126:0); ventral margin of the ventral tubercle narrow and ventrally expanded (i.e., convex) rather than wide and deeply grooved (134:0); capital groove constricted rather than wide (137:1). Additional proposed apomorphies which are present in Mancalla cedrosensis and two additional associated specimens (SDSNH 77966 and LACM 128870) referable to Mancalla but not to species include: ulna shorter than carpometacarpus (180:1); ulna and radius more dorsoventrally compressed than other alcids; extension of the dorsal ulnar condyle farther distally to the ventral ulnar condyle than in other alcids (182:0); pisiform process of carpometacarpus reduced or absent (188:1).