Mollusc species from the Pontocaspian region - an expert opinion list Author Wesselingh, Frank Naturalis Biodiversity Center, Leiden, Netherlands Author Poorten, Jan Johan ter Field Museum of Natural History, Chicago, United States of America Author Kijashko, Pavel Moscow State University, Moscow, Russia Author Albrecht, Christian Justus Liebig University, Giessen, Germany Author Anistratenko, Olga Yu Schmalhausen Instite of Zoology, National Academy of Sciences of Ukraine, Kiev, Ukraine & Institute of Geological Sciences, National Academy of Sciences of Ukraine, KievUkraine Author Frolov, Pavel Saint-Petersburg State University, Saint Petersburg, Russia Author Gándara, Alberto Martinez Grigore Artipa National Museum of Natural History, Bucharest, Romania Author Gittenberger, Arjan Gittenberger Marine Research, Inventory & Strategy, Leiden, Netherlands Author Gogaladze, Aleksandre Naturalis Biodiversity Center, Leiden, Netherlands Author Mikhail Karpinsky Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia Author Popa, Luis Grigore Antirpa National Museum of Natural History, Bucharest, Romania Author Sands, Arthur F Justus Liebig University, Giessen, Germany Author Vandendorpe, Justine Justus Liebig University, Giessen, Germany Author Wilke, Thomas Justus Liebig University Giessen Germany text ZooKeys 2019 827 31 124 http://dx.doi.org/10.3897/zookeys.827.31365 journal article http://dx.doi.org/10.3897/zookeys.827.31365 1313-2970-827-31 10B663895E424E5287D8F49E2405D651 10B663895E424E5287D8F49E2405D651 Cerastoderma sp. A [non C. rhomboides (Lamarck, 1819)] 1916 Cardium edule var. nuciformis Milaschewitch: 257-259, pl. 7, figs 7, 8 [non Cardium nuciforme d'Orbigny , 1850]. 2003 Cerastoderma rhomboides rhomboides (Lamarck, 1819). - Andreeva and Andreev: 93, fig. 6.1(A) [non Cardium rhomboides Lamarck, 1819]. 2013 Cerastoderma rhomboides (Lamarck, 1819). - Kijashko in Bogutskaya et al.: 343, fig. 127, photo 40 [non Lamarck, 1819]. 2016 Cerastoderma rhomboides (Lamarck, 1819). - Vinarski and Kantor: 70 [non Lamarck, 1819]. Status. Native Pontocaspian species (Black Sea Basin), introduced to Caspian Sea and Aral Sea. Distribution. Black Sea (including Sea of Azov), Caspian Sea, Aral Sea, Aegean. Taxonomic notes. This concerns a common rhomboid-shaped species in the Pontocaspian region whose name is uncertain. It has a short ligament in common with C. glaucum and the persistent occurrence of ribs on the posterior margin, the well-defined character of the ribs and the regular occurrence of scales in common with western European C. edule . This form has been often referred to as C. rhomboides (Lamarck, 1819) that has been described from the Italian Pliocene but that concerns a typical glaucum form (Fig. 2), not the rhomboid form of the Pontocaspian Cerastoderma . The species has been named Cardium edule var. nuciformis by Milaschewitch (1916) , but that name is a junior primary homonym of Cardium nuciforme d'Orbigny , 1850. Even though some morphological features mentioned in the description of C. lamarcki (Reeve, 1845) may resemble those of the Pontocaspian species, the former has been traced to southern Great Britain from where molecular analyses only show the presence of C. glaucum ( Nikula and Vaeinoelae 2003 ). Conservation status. Not assessed.