Ischnochiton tridentatus Pilsbry, 1893

Reyes-Gómez, Adriana, Vargas-Ponce, Ofelia, Galván-Villa, Cristian, Salgado-Barragán, José, Esqueda-González, Ma. Del Carmen & Ríos-Jara, Eduardo, 2023, Inventory of chiton species (Polyplacophora) from the rocky intertidal of the Northern Gulf of California, with an illustrated taxonomic key, Zootaxa 5296 (2), pp. 147-178 : 153

Ischnochiton tridentatus Pilsbry, 1893

( Figure 2B )

Ischnochiton (Radsiella) tridentatus Pilsbry, 1893: 35–39 . Chresonymy and synonymy in Kaas & Van Belle (1990).

Type material. Lectotype, designated by Kaas & Van Belle (1990), ANSP 66324 .

Type locality. La Paz, Baja California Sur, México ( Kaas &Van Belle 1990) .

Material examined. Seventy– six specimens, BL 7.3–20.2 mm.

Habitat. In the superficial intertidal on medium–sized and small rocks buried in sand. Specimens were collected from numerous loose rocks with dense patches of globular thalli (maximal diameter of 20 cm) of the alga Dictyosphaeria Decaisne, 1842 .

Remarks. Ischnochiton tridentatus has a sculpture of concentric zigzag lines and variable tegmentum color of light olive, dark green and gray ( Fig. 2B ).

Kaas & Van Belle (1990) reported the distribution of this species throughout the Gulf of California, including Mazatlán. However, recent studies have shown that I. tridentatus is absent in Mazatlán, while it is abundant at La Paz, Baja California Sur (García-Ríos & Álvarez-Ruiz 2007). In the present study, it was only registered at Bahía San Carlos, Sonora. The maximal size measured is 26.1 mm, coinciding with previous reports by Kaas & Van Belle (1990).

Ischnochiton tridentatus is endemic to the Gulf of California. In our surveys, it was common to find small (maybe juveniles) and adult specimens cohabiting at beaches with low wave energy.

Figures

FIGURE 2. Chiton species obtained from the Northern Gulf of California. A. Dorsal and lateral views of Ischnochiton guatemalensis CUCBACM 00450. B. Dorsal and lateral views of Ischnochiton tridentatus CUCBACM 00453. C. Dorsal and lateral views of Stenoplax limaciformis CUCBACM 00455. D. Dorsal and lateral views of Stenoplax mariposa CUCBACM 00459. E. Dorsal and lateral views of Stenoplax sonorana CUCBACM 00462. F. Dorsal view of Lepidozona clathrata CUCBACM 00464. G. Dorsal view of Lepidozona serrata CUCBACM 00471. H. Dorsal and lateral views of Lepidozona subtilis CUCBACM 00475. I. Dorsal and lateral views of Callistochiton elenensis CUCBACM 00476.