The Late Pleistocene mollusk fauna of Selitrennoye (Astrakhan province, Russia): A natural baseline for endemic Caspian Sea faunas Author van de Velde, Sabrina Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, the Netherlands sabrina.vandevelde@naturalis.nl Author Yanina, Tamara A. Moscow State University, Faculty of Geography, Leninskie Gory, 1, 119991 Moscow, Russia Author Neubauer, Thomas A. Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, the Netherlands & Department of Animal Ecology and Systematics, Justus Liebig University, Heinrich-Buff-Ring 26 - 32 IFZ, 35392 Giessen, Germany Author Wesselingh, Frank P. Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, the Netherlands text Journal of Great Lakes Research 2020 2020-10-31 46 5 1227 1239 http://dx.doi.org/10.1016/j.jglr.2019.04.001 journal article 5982 10.1016/j.jglr.2019.04.001 6d7090a8-a7b0-40b5-81f6-8d8e6fdc55f7 5019200 Didacna subcrassa Pravoslavlev, 1939 ( Fig. 5 : 1). *1939 Didacna subcrassa Pravoslavlev : 227 , pl. 4, figs. 6–11. 1983 Didacna subcrassa Pravoslavlev, 1939 – Popov: 199 , pl, 8, figs. 11–16. 2007 Didacna subcrassa subcrassa Pravoslavlev, 1939 – Nevesskaja: 920 , pl. 16, figs. 14–18. Dimensions – max. L 32.5 mm , H 25.5 mm . Characterization – Thin-shelled subtrapezoid to subovate to subtrigonate species, usually flat and trigonoid in juvenile stages. The posterodorsal keel is poorly delimited, the low angle posterior bend is rounded. The posterior ridge is subrounded. It is more pronounced in juvenile stages and fading in adult stages. The species has 19–26 posterior ribs. Interspaces are about half to equal width of the ribs. Anterior ribs are sometimes poorly developed and rib width increases towards the posterior keel. Beak is protruding, the hinge is thin. The location of the semidiameter in juveniles is on the posterior ridge but in adults becomes located towards the center of the shell. Ecology – Unknown (extinct).