The polyclads (Platyhelminthes: Polycladida) from the Tropical Eastern Pacific: Commented checklist and description of a new species Author Ramos-Sánchez, Mariela E9D05B3F-CF64-48E3-B5ED-8D24E47F9D2A Doctorado en Ciencias Biológico Agropecuarias, Área Ciencias Biológico Agropecuaria y Pesquera, Ciudad de la cultura “ Amado Nervo ”, Tepic, Nayarit, 63000, Mexico. & Laboratorio de Sistemática de Invertebrados Marinos (LABSIM), Universidad del Mar, campus Puerto Ángel, Ciudad Universitaria, Puerto Ángel, Oaxaca, 70902, Mexico. rmariela220@gmail.com text European Journal of Taxonomy 2024 2024-10-17 962 1 1 67 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2683/12419 journal article 10.5852/ejt.2024.962.2683 2118-9773 13947260 40171C5B-90EB-4641-91FF-EA8CA2C60D23 Euplanoida pacificola ( Plehn, 1896 ) Leptoplana pacificola Plehn, 1896: 153–155 , figs 7–9, pl. 13 fig. 10 ( type locality: Valparaíso , Chile ). Discoplana pacificola – Bock 1913: 220 (new combination). Euplana pacificola – Hyman 1953a: 332–333 , figs 87–89 (new combination, description and new record from Point San Marcial reef, Baja California Sur , Miramar Beach, Guaymas, Sonora , Mexico ). Euplanoida pacificola – Faubel 1983: 33–36 , fig. 3e (new combination, identification keys). — Brusca 2005: 69 (checklist). Distribution Valparaíso , Chile ; Coast of Peru ; Point San Marcial reef, Baja California Sur , Miramar Beach, Guaymas, Sonora , Mexico . Habitat Fouling (adhered to the keel of a vessel ( Plehn 1896 )), benthic ( Hyman 1953a ). Remarks Plehn (1896) initially described Euplanoida pacificola in Valparaíso , Chile , after collecting specimens on the keel of a ship. The species was subsequently recorded along the coast of Peru , initially considered to be a variety of E. pacificola . Hyman (1953a) later reported it from the coast of the Gulf of California, identifying the species as a Mexican variant. However, Hyman (1953a) overlooked possible morphological differences in the reproductive system and the geographic distribution. She argued that such variations and geographic distribution did not justify separation into distinct species. Based on a review of the descriptions and illustrations provided by Plehn (1896) and Hyman (1953a) , this study suggests a detailed review and comparison of the biological material assigned to Euplanoida pacificola , as differences were found in the distribution of the cerebral and tentacular eyes, the morphology of the pharynx, the penis papilla and Lang’s vesicle (review the work of Ramos-Sánchez et al . 2019 ). In addition, it is necessary to review the structure identified as Lang’s vesicle, since Plehn (1896) describes it as a bursa copulatrix.