The presence of Dinogymnium (Dinophyceae) in Lower Cretaceous sediments from the northwest Tethys (southeast France and western Switzerland) and Gulf of Mexico areas: stratigraphic and systematic consequences

Abstract

Palynological investigations of two Lower Cretaceous surface sections from the northwestern Tethyan area, Châtel-Saint-Denis (western Switzerland) and Vergons (southeast France), have yielded specimens of the fossil dinoflagellate Dinogymnium. These established in-situ occurrences in Hauterivian ammonite-dated sediments represent the first formal record of this genus in the Lower Cretaceous in the Tethyan area. A re-examination of the assemblages studied by Riley and Fenton (1984) from DSDP Site 535 in the Gulf of Mexico, has confirmed the in-situ occurrence of Dinogymnium in Upper Berriasian, Valanginian and Hauterivian sediments. Their comparison with the Tethyan material establishes the occurrence of Dinogymnium in the Lower Cretaceous of the Tethys-Atlantic area and leads us to reconsider the earliest occurrence of Dinogymnium which was previously generally accepted to be at the base of the Upper Cretaceous. Two new species are erected: Dinogymnium aerlicum and Dinogymnium vergonsense. Morphological, stratigraphical and palaeogeographical comparisons are made with other rare Early Cretaceous records of Dinogymnium, as well as with other, younger species of the genus.