Preliminary observations of cyst-theca relationships in Spiniferites ramosus and Spiniferites membranaceus (Dinophyceae)

Motile thecal cells derived from the hatching of single cysts identified as Spiniferites membranaceus and S. ramosus have been used to establish cultu res. These cultures were examined in order to assess the cyst-theca relatio nships of these two taxa. The cultures produced two different motile Gonyau lax species belonging to Kofoid's Spinifera group. These cultures were then induced to form a new cyst generation under uniform conditions, and examin ation of large numbers of the resulting cysts has shown that process develo pment is an extremely variable phenomenon although process morphologies dis play a continuum within a species. Process length (and to a certain degree, process morphology) requires careful interpretation when used to discrimin ate Spiniferites taxa, in both modern and ancient environments.