Lepidozona serrata

Lepidozona serrata (Carpenter, 1864)

(Figures 2G, 6G–L)

Ischnochiton serratus Carpenter, 1864: 517–686. Chresonymy and synonymy in Ferreira (1974).

Type material. The holotype (USNM 16204) is lost according to Kaas & Van Belle (1987). Paratype, PRM 98.

Type locality. Cabo San Lucas, Baja California Sur, México.

Material examined. Three specimens, BL 7.9–8.7 mm.

Habitat. In the intertidal on medium–sized rocks buried in sand, with brown and red crusty algae patches.

Remarks. The tegmentum of Lepidozona serrata is usually eroded; it exhibits a fine sculpture of radial low ribs (Figs. 6G–I). The posterior margin of the head and intermediates valves displays 8–9 longitudinally arranged denticles (Figs. 6G–H); central areas with net–like sculpture and smooth jugal area (Figs. 6H–I); lateral areas somewhat raised with 3 radial fine grooves (Fig. 6H). Girdle with small, bent dorsal scales with small, rounded spheres aligned longitudinally towards its distal edge (Fig. 6K). Radula with unicuspid major lateral teeth; the central tooth is larger than the minor lateral tooth, which is distally bilobulated (Fig. 6L).

Ferreira (1974) reported the distribution of this species from San Diego, California, to Magdalena Bay on the west coast of Baja California (BC), from the interior of the Gulf of California, from San Luis Gonzaga to Cabo San Lucas, including Punta Chivato of Bahía Concepcion, Bahía Kino, Guaymas, Mazatlán and the islands of Espíritu Santo, San Francisco, Carmen, Coronados, Tiburón and Tres Marías. Kaas & Van Belle (1987) considered the same distribution and added that it is "continuously" distributed throughout the Gulf of California. In the present study, only three L. serrata individuals were registered from two sites: Playa las Palmas and Bahía Kino, both in Sonora.

Pilsbry (1892) considered L. serrata as a member of the genus Ischnochiton, because according to him, the species is smaller than other species of Lepidozona. Ferreira (1974) and Pilsbry (1892) identified significant morphological differences between L. serrata and the diagnostic characteristics of the genus Lepidozona. Both authors considered that the few similarities that L. serrata shares with the other members of the genus Lepidozona might be the result of convergences and a possible polyphyletic origin of the genus. Moreover, other Lepidozona species have a reduced number of ribs on the lateral areas (2–4) and the postmucronal area of the tail valve (8–6 ribs). In addition, the girdle scales are much smaller (200 μm) than those observed in the other species of the genus.