Pitar morrhuanus
Similar to Mercenaria campechiensis. Pitar morrhuanus has anterior lateral teeth not found in M. campechiensis, as well as its posterior tooth (4b) on the left valve being separate from the nymph.
Similar to Mercenaria mercenaria. Pitar morrhuanus is distinguishable by the presence of lateral teeth on both valves and the presence of comarginal ribs throughout the dissoconch.
Similar to Pitar fulminatus. Pitar morrhuanus is distinguishable by its more convex posterior dorsal margin, more prominent umbones and dull exterior. Its umbones are also curved more anteriorly than those of P. fulminatus, and P. morrhuanas lacks the dark brown coloration at its posterior dorsal margin and lunule typically found in P. fulminatus.
Similar to Pitar patagonicus. Pitar morrhuanus is more ovate in shape and has less robust hinge plates. In addition, P. morrhuanus has only one bifid tooth (3b); whereas, P. patagonicus can have up to three bifid teeth (2a, 1, 3b).
The overall shape is subtrigonal ovate. The anterior, ventral and posterior margins are rounded. The anterior dorsal margin is straight and the posterior dorsal margin is convex. The valves are equal in size and shape (equivalve), and there is no gape when they are closed. Sculpture consists of growth lines and very fine, dense comarginal ribs covering the flank. The ribs become more prominent ventrally. The lunule is teardrop-shaped, extends 2/3 of the anterior dorsal margin and is defined by a fine shallow groove. The umbo is anterior, and the beaks also point slightly to the anterior. The escutcheon is not well defined.
The exterior is white with a gray or brown periostracum. The interior is also white.
The ligament is external, but slightly sunken; it extends 2/3 of the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth (2a, 2b, 4b), none of which are bifid. The central tooth (2b) is the most prominent, and it is fused with the anterior tooth (2a) dorsally, forming an inverted "V" shape. There is also one anterior lateral tooth (A2) on the left valve. On the right valve, there are three cardinal teeth: the anterior (3a) and central (1) teeth are not bifid, and the posterior tooth (3b) is bifid. There are also two anterior lateral teeth (A1, A3) on the right valve. A fine ridge runs parallel to the posterior dorsal margin on both valves, but it is more prominent on the right valve. The anterior and posterior adductor muscle scars are similar in area, but the posterior is more rounded than the anterior. The pallial sinus is tapering and extends to the middle of the nymph in length.
Pitar morrhaunus is found in the Northwest Atlantic.