Author	Harding, I.C.
Year	1996
Journal	Review of Palaeobotany and Palynology, Volume 92, nos. 3-4: 351-366Review of Palaeobotany and Palyn
Title	Taxonomic stabilisation of dinoflagellate cyst taxa, as exemplified by two morphologically complex Early Cretaceous species

Abstract Harding, I.C., 1996; Taxonomic stabilisation of dinoflagellate cyst taxa, as exemplified by two morphologically complex Early Cretaceous species. Review of Palaeobotany and Palynology, Volume 92, nos. 3-4: 351-366 Both Nelchinopsis kostromiensis and Gardodinium trabeculosum show a complex morphology which has proved difficult to understand using conventional light microscopy (LM), and has resulted in a degree of taxonomic flux. LM examination of type material and combined LM and electron microscopic observation of the new topotype and additional uncompressed specimens has resulted in a detailed redescription of these two taxa including determination of their paratabulation. Both Nelchinopsis kostromiensis (Vozzhennikova) Wiggins, emend. nov. and Gardodinium trabeculosum (Gocht) Alberti, emend. nov. display ornatum-type paratabulation, and additionally can be assigned to the dinoflagellate subfamily Leptodinioideae. These two taxa are the only fossil dinocysts so far described which show parasutural features developed on ectophragmal wall layers and hence to further improve dinocyst systematics. The species concerned both illustrate the problems of "taxonomic evolution". Nelchinopsis kostromiensis can also be found in the literature assigned to the genera Gonyaulax and Gonyaulacysta, and even as the species Alaskadinium wigginsii. Gardodinium trabeculosum was initially placed in the genus Scriniodinium and was then made the type of the genus Gardodinium. The species was subsequently transferred to the genus Chlamydophorella when Gardodinium was viewed as a junior synonym of Chlamydophorella, currently many workers view the type specimen of the species trabeculosum as the type of the genus Gardodinium. The chequered history of both species is more exhaustively documented in brief introductions to each morphotype in order to show the evolution of the systematics of these forms. The emended descriptions given here are based on observation of type and topotype material in addition to study of new specimens which were found during routine biostratigraphic examination of Lower Cretaceous samples, many of the specimens showing preservation in three dimensions. All newly figured specimens have been allocated catalogue numbers (e.g. X. 26030), and will be deposited in the Sedgwick Geology Museum, Cambridge University. Use of Taylor-Evitt paratabulation notation and the terms "ectophragm" and "autophragm" follow the sense of Evitt (1985).