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Hadriana
From Fensome et al., 2019:
Hadriana, Riding and Helby, 2001f, p.153–155.
Type: Riding and Helby, 2001f, figs.8G–I, as Hadriana
cinctum.
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Original description:
Diagnosis:
Large dinoflagellate cysts which comprise a subspherical to ellipsoidal cyst body. A prominent ectophragm, which is perforate to trabeculate and is open antapically, emerges in the lower part of the precingular paratplate series and extends below the cyst body. The ectophragm may be connected to the cyst body by paracingular (?) and postcingular processes. The ectophragm and autophragm are closely appressed in the apical paraplate series.
The paratabulation is gonyaulacacean, indicated by the intratabular processes, where developed, and the principal archaeopyle suture.
Apical archaeopyle; operculum free.
The parasulcus is flat to slightly indented.
Remarks:
Hadriana is a large, morphologically complicated, variable and extremely distinctive genus. It is similar in many respects to Belowia Riding & Helby (this volume) and it seems likely that the Tithonian Belowiamay have evolved from Hadriana (Riding & Helby, this volume, b). Both Belowia and Hadirana are thought to be related to Rigaudella Below 1982 (see Comparison of Hadriana cincta, below) The ectophragm is highly variable, from perforate to trabeculate and it may be connected to the autophragm of the cyst body by intratabular processes in the paracingular (?) and postcingular paraplate series. A large, subcircular to ellipsoidal, antapical hole is generally present in the ectophragm, which separates from the autophragm close to the base of the precingular paraplate series. Therefore, the ectophragm forms an extensive belt or girdle, surrounding all of the hypocystal autophragm.
Affinities:
The Tithonian Belowia Riding & Helby (this volume) is closely related to Hadriana. They share a small, essentially smooth epicyst, devoid of processes and the fact that wall separation occurs close to the base of the precingular paraplates. Although there are marked hypocystal differences, these genera both display major ectophragmal development at and below the pracingulum. However, Hadriana lacks the paracingular tunnel, which characterises all morphotypes of Belowia; it does not display large processes and the ectophragm is widely open antapically (around twice diameter of autocyst). Eatonicysta Stover & Evitt 1978 emend. Stover & Williams 1995 is reminiscent of Hadriana in having an apical archaeopyle and a large ectophragmal covering supported by intratabular processes in all the major paraplate series. However, Hadirana is larger, oblate and lacks epicystal processes and reduced hypocystal processes. The ectophragm in Hadriana is generally open antapically. Reticulatosphaera Matsuoka 1983 is also similar in morphology to Hadriana, however the former is smaller, has a precingular archaeopyle and has about 26, apparently intratabular processes. The periphragm of Disphaeria Cookson & Eisenack 1960 emend. Norvick 1973 has a large dorsal opening, and this genus has a precingular archaeopyle. Hadriana differs from trabeculate complex chorate dinoflagellate cyst genera such as Adnatosphaeridium Williams & Downie 1966, Hapsidaulax Sarjeant 1975, Hystrichosphaerina Alberti 1961, Polystephanephorus Sarjeant 1961 and Rigaudella Deflandre emend. Below 1982, in lacking large intratabular processes or process complexes representing the major epicystal paraplate series and in having a dense equatorial trabeculum. In Hadriana , the paracingular and postcingular processes are largely subsumed into the ectophragm. The Palaeogene genus Riculacysta Stover 1977, like Hadriana, has a trabeculate ectophragm especially well developed on the hypocyst and an apical archaeopyle (Stover, 1977). Riculacysta, however, is a distinctly chorate form, which bears solid processes on the ventrolateral and lateral surfaces.
Hadriana, Riding and Helby, 2001f, p.153–155.
Type: Riding and Helby, 2001f, figs.8G–I, as Hadriana
cinctum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description:
Diagnosis:
Large dinoflagellate cysts which comprise a subspherical to ellipsoidal cyst body. A prominent ectophragm, which is perforate to trabeculate and is open antapically, emerges in the lower part of the precingular paratplate series and extends below the cyst body. The ectophragm may be connected to the cyst body by paracingular (?) and postcingular processes. The ectophragm and autophragm are closely appressed in the apical paraplate series.
The paratabulation is gonyaulacacean, indicated by the intratabular processes, where developed, and the principal archaeopyle suture.
Apical archaeopyle; operculum free.
The parasulcus is flat to slightly indented.
Remarks:
Hadriana is a large, morphologically complicated, variable and extremely distinctive genus. It is similar in many respects to Belowia Riding & Helby (this volume) and it seems likely that the Tithonian Belowiamay have evolved from Hadriana (Riding & Helby, this volume, b). Both Belowia and Hadirana are thought to be related to Rigaudella Below 1982 (see Comparison of Hadriana cincta, below) The ectophragm is highly variable, from perforate to trabeculate and it may be connected to the autophragm of the cyst body by intratabular processes in the paracingular (?) and postcingular paraplate series. A large, subcircular to ellipsoidal, antapical hole is generally present in the ectophragm, which separates from the autophragm close to the base of the precingular paraplate series. Therefore, the ectophragm forms an extensive belt or girdle, surrounding all of the hypocystal autophragm.
Affinities:
The Tithonian Belowia Riding & Helby (this volume) is closely related to Hadriana. They share a small, essentially smooth epicyst, devoid of processes and the fact that wall separation occurs close to the base of the precingular paraplates. Although there are marked hypocystal differences, these genera both display major ectophragmal development at and below the pracingulum. However, Hadriana lacks the paracingular tunnel, which characterises all morphotypes of Belowia; it does not display large processes and the ectophragm is widely open antapically (around twice diameter of autocyst). Eatonicysta Stover & Evitt 1978 emend. Stover & Williams 1995 is reminiscent of Hadriana in having an apical archaeopyle and a large ectophragmal covering supported by intratabular processes in all the major paraplate series. However, Hadirana is larger, oblate and lacks epicystal processes and reduced hypocystal processes. The ectophragm in Hadriana is generally open antapically. Reticulatosphaera Matsuoka 1983 is also similar in morphology to Hadriana, however the former is smaller, has a precingular archaeopyle and has about 26, apparently intratabular processes. The periphragm of Disphaeria Cookson & Eisenack 1960 emend. Norvick 1973 has a large dorsal opening, and this genus has a precingular archaeopyle. Hadriana differs from trabeculate complex chorate dinoflagellate cyst genera such as Adnatosphaeridium Williams & Downie 1966, Hapsidaulax Sarjeant 1975, Hystrichosphaerina Alberti 1961, Polystephanephorus Sarjeant 1961 and Rigaudella Deflandre emend. Below 1982, in lacking large intratabular processes or process complexes representing the major epicystal paraplate series and in having a dense equatorial trabeculum. In Hadriana , the paracingular and postcingular processes are largely subsumed into the ectophragm. The Palaeogene genus Riculacysta Stover 1977, like Hadriana, has a trabeculate ectophragm especially well developed on the hypocyst and an apical archaeopyle (Stover, 1977). Riculacysta, however, is a distinctly chorate form, which bears solid processes on the ventrolateral and lateral surfaces.