MIOCENE DINOFLAGELLATE STRATIGRAPHY AND SYSTEMATICS OF MARYLAND AND VIRGINIA .2. HOMOLOGY AND STRUCTURE IN DINOFLAGELLATE CYST TERMINOLOGY

Research over the past three decades has produced a rich vocabulary fo r describing dinoflagellate cysts. Ideas about homology have exerted a strong influence on the development of this terminology. From wall st ructure to tabulation, some of these ideas are inconsistent with homol ogy concepts in contemporary evolutionary biology. In this selective r eview of the descriptive terminology for fossil dinoflagellates, a pra ctical and theoretically consistent terminology is proposed from among the present plurality of terms. We perceive tabulation as the number, distribution and topology of thecal plates and cyst fields because th e expression of these characters is the same for both the motile plano zygote and the non-motile cyst. The Kofoid system of labeling tabulati on elements is favored over the Taylor-Evitt approach, where specific homologies must be assumed present between naturally occurring tabulat ions and the model. We apply the results of our analysis in descriptio ns of 12 morphologically diverse new taxa from the Miocene of Maryland and Virginia. The new genus Cousteaudinium is erected with Cousteaudi nium aubryae as the type. The taxon Labyrinthodinium truncatum Piaseck i 1980 is emended and a new subspecies, Labyrinthodinum truncatum subs p, modicum is described. The other new species are: Cannosphaeropsis p assio. Cerebrocysta poulsenii, Cerebrocysta satchelliae, Exochosphaeri dium insigne, Impagidinium antecarcerem, Impagidinium arachnion, Lingu lodinium multivigratum, Pyxidiniopsis fairhavenensis, Spiniferites sol idago and Sunatradinium hamulatum.