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Review of the fossil dinoflagellate Cleistosphaeridium.
| Islam, M.A. | |
| 1993 | |
| Revista Espa±ola de Micropaleontologica, Vol.XXV, n¨m.2, pp.81-94 | |
| Review of the fossil dinoflagellate Cleistosphaeridium. |
Islam, M.A., 1993: Review of the fossil dinoflagellate Cleistosphaeridium. Revista Espa±ola de Micropaleontologica, Vol.XXV, n¨m.2, pp.81-94 Abstract: Inconsistencies between the stated and illustrated morphology of Cleistosphaendium led to re-photographing the holotype of Cleistosphaendium diversispinosum, the genotype. The new photomicrographs revealed that the type specimen possesses only solid processes which are often proximally joined in arcuate process complexes implying their penitabular distribution. In view of this new information. C. diversispinosum is reattributed to Systematophora. With the transfer of the type species to another genus, Cleistosphaeridium became superfluous, and reallocation of its species to other genera as appropriate is called for. A literature search further revealed that morphologically varied cysts that are separable in distinctive morphological groups had been referred to Cleistosphaeridium. It is also found that Impletosphaeridium, hitherto known as having uncertain archeopyle, in fact possesses an apical archeopyle displayed by the illustrated paratype of the type species, Impletosphaendium transfodum. The diagnosis of Impletosphaeridium is accordingly emended and 29 species of former Cleistosphaendium are reallocated to Impletosphaeridium. All pre-existing species of Impletosphaeridium with unknown archeopyles are provisionally retained. Of the remaining species of former Cleistosphaeridium, two species are transferred to Circulodinium, 3 species to Heterosphaeridium including one subspecies upgraded, and 5 species to Sentusidinium. For the species still unallocated, two new genera are proposed: Downiesphaeridium n. gen. for cysts possessing nontabular tapering hollow and closed processes that accommodated 6 species, and Sepispinula n. gen. for cysts possessing hollow septate processes, accommodating 2 species and a subspecies.