Two new ceratioid cornucavate dinoflagellate cysts from the Upper Cretaceous, Gulf of Suez, Egypt

Abstract

Diverse and well-preserved assemblages of organic-walled dinoflagellate cysts have been recovered from the Matulla Formation (Coniacian – Santonian), Gulf of Suez, Egypt. Among the abundant dinoflagellate cyst assemblages, the new species Odontochitina elbeialyi sp. nov. and Odontochitina ornata sp. nov. (Family Ceratiaceae) are described. The two new species are unique by having a granulate periphragm and three prominent horns. The horns are truncated distally and devoid of striae, ridges and perforations. Odontochitina elbeialyi sp. nov. is characterized by a weakly expressed tabulation on the pericyst indicated by the occasional presence of sutural lines or low ridges indicating the cingulum (two transverse ridges), at plate boundaries. Odontochitina ornata sp. nov. differs from the former, particularly by its clear tabulation, which is corniform gonyaulacoid and more strongly expressed by sutural ridges, and by rare short (rudimentary) sutural (mostly gonal) nipple-like, to truncated processes. Based on the current material, Odontochitina elbeialyi sp. nov. and Odontochitina ornata sp. nov. have short stratigraphic ranges and may therefore be considered as stratigraphic markers for the late Santonian (Late Cretaceous). Their comparison with all formally published species of the genus Odontochitina is presented and discussed, and the associated relevant dinoflagellate cyst taxa are also indicated. The paleoenvironmental significance of the Odontochitina elbeialyi sp. nov. and Odontochitina ornata sp. nov. is discussed.