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Downiesphaeridium
From Fensome et al., 2019:
Downiesphaeridium, Islam, 1993, p.83.
Emendation: Masure in Fauconnier and Masure, 2004, p.195.
Type: Islam, 1983b, pl.2, fig.1, as Cleistosphaeridium spinulastrum.
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Original description: [Islam, 1993]:
Diagnosis:
Spherical to subspherical dinoflagellate cysts; auto or biphragmal, psilate or ornamented (chagrinate, echinate, granulate, reticulate); skolochorate; possesses many nontabular processes which are hollow, taeniate, tapering or attenuate with broader bases, distally acuminate, rimmed or simple, both ends closed; processes in individual specimens are similar in size and shape; tabular features other than the tA or (tA) type apical archeopyle are normally absent.
Affinities:
Downiesphaeridium resembles Dapsilidinium Bujak, Downie, Eaton and Williams, 1980 but differs in possessing attenuate/tapering and distally closed processes. Conosphaeridium Cookson and Eisenack, 1969 possessing hollow closed conical processes differ from the new genus in having fewer broader processes and a precingular archeopyle.
Remarks:
Creation of the new genus was considered necessary to accommodate the dinoflagellate cysts possessing attenuate/tapering hollow closed processes and apical type tA or (tA) archeopyle, and appropriate as these cysts do not conform to the morphology of any existing fossil dinoflagellate genera.
Downiesphaeridium, Islam, 1993, p.83.
Emendation: Masure in Fauconnier and Masure, 2004, p.195.
Type: Islam, 1983b, pl.2, fig.1, as Cleistosphaeridium spinulastrum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Islam, 1993]:
Diagnosis:
Spherical to subspherical dinoflagellate cysts; auto or biphragmal, psilate or ornamented (chagrinate, echinate, granulate, reticulate); skolochorate; possesses many nontabular processes which are hollow, taeniate, tapering or attenuate with broader bases, distally acuminate, rimmed or simple, both ends closed; processes in individual specimens are similar in size and shape; tabular features other than the tA or (tA) type apical archeopyle are normally absent.
Affinities:
Downiesphaeridium resembles Dapsilidinium Bujak, Downie, Eaton and Williams, 1980 but differs in possessing attenuate/tapering and distally closed processes. Conosphaeridium Cookson and Eisenack, 1969 possessing hollow closed conical processes differ from the new genus in having fewer broader processes and a precingular archeopyle.
Remarks:
Creation of the new genus was considered necessary to accommodate the dinoflagellate cysts possessing attenuate/tapering hollow closed processes and apical type tA or (tA) archeopyle, and appropriate as these cysts do not conform to the morphology of any existing fossil dinoflagellate genera.