Morphology of species ofLitosphaeridium(Cretaceous, Dinophyceae)

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Abstract
Litosphaeridium is a genus of skolochorate dinoflagellate cysts characterized by an apical archeopyle and 16 to about 45 basically intratabular hollow processes that are conical, cylindrical, or bulbous, with subcircular cross‐sections and simple tips. Other indications of paratabulation are absent and, depending upon the species, some paraplates may be without processes while others may be represented by as many as four. Typically, the species are highly variable in details, especially showing many small differences in process number and position. Analysis of six species and one subspecies here assigned to Litosphaeridium suggests that a similar pattern of gonyaulacoid paratabulation can be discerned in each of them. This pattern is distinct from that of other skolochorate cysts and analogous in detail with the epithecal tabulation of Gonyaulax polyedra. Paratabulation, along with similarities in process and wall structure, support the position that these six species can be included in one genus. Species of Litosphaeridium have been found in Albian, Cenomanian, Turonian, and Maestrichtian strata. New taxa described are: Litosphaeridium bacar n. sp. and Litosphaeridium siphoniphorum subp. glabrum n. subsp. Previously described taxa reinterpreted here are: Litosphaeridium siphoniphorum subsp. siphoniphorum, Litosphaeridium conispinum, Litosphaeridium arundum, Litosphaeridium fenestreconum n. comb., and Litosphaeridium sp. of Stein.