New organic-walled dinoflagellate cysts from recent sediments of central Asian seas

Abstract

Recent to sub-recent sediments from the Caspian Sea, the Kara-Bogaz-Gol Bay, the Enseli lake and the Aral Sea contain the new organic-walled dinoflagellate cysts Caspidinium, Caspidinium rugosum and Impagidinium caspienense. Caspidinium rugosum has S-type paratabulation, dextral torsion and low relief intratabular ornamentation. Impagidinium caspienense has low intratabular suturo-cavate relief, parasutural septa irregular in height and a high septum at the junction of paraplate 1'''' and the sulcus. The accompanying species consist of Spiniferites cruciformis, Lingulodinium machaerophorum, Pyxidinopsis psilata, cysts of Pentapharsodinium dalei and Brigantedinium spp. Spiniferites cruciformis varies from specimens with a cruciform body with a well-developed postero-lateral membranous flange to specimens with a pear-shaped body, reduced processes and no flange. Sea-surface data from these Central Asian seas suggests that the two new taxa Caspidinium rugosum and Impagidinium caspienense are probably related to low salinity conditions (12-13).