Dreissena elata

Wesselingh, Frank, Poorten, Jan Johan ter, Kijashko, Pavel, Albrecht, Christian, Anistratenko, Olga Yu, Frolov, Pavel, Gándara, Alberto Martinez, Gittenberger, Arjan, Gogaladze, Aleksandre, Mikhail Karpinsky, Popa, Luis, Sands, Arthur F, Vandendorpe, Justine & Wilke, Thomas, 2019, Mollusc species from the Pontocaspian region - an expert opinion list, ZooKeys 827, pp. 31-124 : 55-56

Dreissena elata Andrusov, 1897

*1897 Dreissensia polymorpha var. elata Andrusov: 353, pl. 20, fig. 25.

1969 Dreissena elata (Andr.). - Logvinenko and Starobogatov: 316, fig. 341(1).

1994 Dreissena elata Andrusov, 1897. - Rosenberg and Ludyanskiy: 1482, fig. 3g.

2013 Dreissena elata (Andrusov, 1897). - Kijashko in Bogutskaya et al.: fig. 108.

2016 Dreissena (Dreissena) elata (Andrusov, 1897). - Vinarski and Kantor: 76.

Status. Pontocaspian species, endemic to the Caspian Sea, probably extinct. Species status uncertain.

Type locality. Kuuli Cape, Dazmyk, Apsheron Peninsula, Azerbaijan ( Vinarski and Kantor 2016).

Distribution. Caspian Sea. Probably extinct.

Taxonomic notes. Dreissena elata has morphological features in common with D. polymorpha , including a relatively wide shell and a well-pronounced keel located close to the ventral margin. However, the D. elata shell is in general wider, flatter, and has a more rounded abapical margin even though shell characters are higly variable. Dreissena elata has been reported from areas in the Caspian Sea with salinities well above 5 ‰, which is unusual for D. polymorpha elsewhere. We are uncertain whether D. elata might be a sibling species. Its apparently distinct morphology and autecological preferences suggest it is different from D. polymorpha , but it will require molecular comparison to investigate whether it concerns a mere morph that has undergone "ecological release" ( Kohn 1972) or is a different species. However, no living specimens of D. elata have been recorded since 1957 ( Kostianoy and Kosarev 2005) when its Caspian habitats were invaded by Mytilaster minimus .

Conservation status. Not assessed. It was reported as extinct by Kostianoy and Kosarev (2005, and references therein). If D. elata is accepted as a valid species, it might qualify for the same conservation status as D. caspia (critically endangered, possibly extinct; von Rintelen and Van Damme 2011b).