Inventory of chiton species (Polyplacophora) from the rocky intertidal of the Northern Gulf of California, with an illustrated taxonomic key Author Reyes-Gómez, Adriana Doctorado en Biosistemática y Manejo de Recursos Naturales y Agrícolas. Author Vargas-Ponce, Ofelia Departamento de Botánica y Zoología. Author Galván-Villa, Cristian Departamento de Ecología Aplicada, Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez 2100, Zapopan, Jalisco, 45200, México. Author Salgado-Barragán, José Laboratorio de Invertebrados Bentónicos, Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, México. Author Esqueda-González, Ma. Del Carmen Departamento de Ecología Aplicada, Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez 2100, Zapopan, Jalisco, 45200, México. Author Ríos-Jara, Eduardo Departamento de Ecología Aplicada, Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Camino Ing. Ramón Padilla Sánchez 2100, Zapopan, Jalisco, 45200, México. text Zootaxa 2023 2023-05-26 5296 2 147 178 http://dx.doi.org/10.11646/zootaxa.5296.2.2 journal article 10.11646/zootaxa.5296.2.2 1175-5326 7973065 624273A6-3028-42C2-ABE2-A18BBF828156 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.