Observations on the Morphology of Fossil Dinoflagellates

Abstract

Widespread but seldom-observed morphological features of fossil dinoflagellates and some hystrichospheres relate to the ways in which the test ruptures, and the manner in which the plate pattern of a motile dinoflagellate is reflected on the cyst that formed within it. Evidence is presented that many post-Paleozoic hystrichospheres are dinoflagellate cysts. Criteria for recognizing fossil dinoflagellates and for distinguishing encysted and free-swimming stages are presented and applied to 112 genera variously described as dinoflagellates, hystrichospheres, or incertae sedis. Selected aspects of the morphology of 22 described and several undescribed genera are illustrated and discussed.