Stenoplax sonorana Berry, 1956

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 : 156

Stenoplax sonorana Berry, 1956

( Figures 2E , 5F–J )

Stenoplax (Maugerella) conspicua (Carpenter MS, Dall, 1879: 281–344. Subespecies sonorana Berry, 1956: 71–74 . Chresonymy and synonymy in Kaas & Van Belle (1990).

Type material. Holotype, SBMNH 34427 , “Berry collection 15131”.

Type locality. Puerto Peñasco , Sonora, México ( Kaas & Belle 1987) .

Material examined. 124 specimens, BL 7.1–14.3 mm.

Habitat. On large and medium–sized rocks semi–buried in sand.

Remarks. This species has a body length ranging from 35–45 mm. The tegmentum has an olive green, dark green, and gray coloration with pink eroded areas. Tegmentum strongly sculptured with concentric corrugated ribs ( Figs. 5F–H ); the lateral areas and the tail valve are elevated showing concentric ribs that break into irregular nodules ( Figs 5G–H ); girdle with elongated spicules ornamented with longitudinal ribs ( Fig. 5I ); central and minor lateral teeth of the radula are elongated short plates ( Fig. 5J ).

Kaas &Van Belle (1987) reported the distribution of this species from Guaymas to the north of the Gulf of California. In the present study, S. sonorana was found at four localities within the region (Bahía San Carlos , Bahía Kino , Puerto Peñasco and de Bahía de los Ángeles ). Only one specimen was obtained from Bahía San Carlos; however, we found numerous specimens in Puerto Peñasco and Bahía de los Ángeles.

Stenoplax sonorana along with S. circumsenta Berry, 1956 , S. fallax Carpenter in Pilsbry, 1892, Stenoplax magdalenensis Hinds, 1845 , Stenoplax conspicua Carpenter in Pilsbry, 1892, and S. heathiana Berry, 1946 are part of a group of large, thick chitons inhabiting the Gulf of California and the west coast of the BC peninsula up to California. This species differs from its congeners by displaying an irregular diamond–like shaped sculpture of the central areas (usually eroded in adult specimens) and by having elongated, curved dorsal girdle spicules.

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.

FIGURE 5. A–E. Scanning electron microscope images of Stenoplax mariposa CUCBACM 00459. A. Dorsal view of head valve. B. Dorsal view of intermediate valve IV. C. Dorsal view of tail valve. D. Dorsal girdle scales (at margin). E. Radular teeth detail. F–J. Scanning electron microscope images of Stenoplax sonorana CUCBACM 00462. F. Dorsal view of head valve. G. Dorsal view of tail valve. H. Detail of central area of intermediate valve IV. I. Dorsal girdle scales. J. Portion of the radula.