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Cryodinium
From Williams et al., 2017:
[Cryodinium, Esper and Zonneveld, 2001, p. 36–37.
This name was also proposed by Esper and Zonneveld (2002, p.201–202).
Type species: Cryodinium meridianum, Esper and Zonneveld, 2001 (pl.3, figs.1–3)]
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Original description: [Esper and Zonneveld, 2001]:
Diagnosis:
Sphaeroidal protoperidinioid cysts with an intercalary archeopyle formed by the loss of the two paraplates 1a and 2a. Surface smooth or granular to scabrate and brown in colour. Single layered wall with low sutures reflecting a peridinioid tabulation pattern of 4′, 3a, 7″, 3c, 5′″, 2″″.
Discussion:
Spheroidal, brown cysts with smooth or slightly granulated single or double layered walls are known to be produced by dinoflagellates of the genus Protoperidinium, which is defined by the tabulation of 4′, 2-3a, 6-7″, 3c, 5″′, 2″″ plus a transitional cingular-sulcal plate (Balech, 1974). Cryodinium gen. nov. fulfills these criteria, but as its cyst–theca relation is presently unknown, we decided to erect a new fossil genus (see later discussion on Cryodinium meridianum gen. nov. sp. nov.) Some modern ‘round brown’ cyst species reflect a peridinioid tabulation pattern as evidenced by the shapes of their hexagonal archeopyles, including cysts of Protoperidinium avelanum and Protoperidinium conicoides ( Balech, 1974). However, they are clearly distinguishable from cysts of Cryodinium by their lack of sutures that reflect a paratabulation. This is also the case for the species of Brigantedinium, which is a fossil genus of round, brown cysts related to Protoperidinium species. Brigantedinium species as well reflect no paratabulation pattern besides the archeopyle ( Reid, 1977). Other paratabulated round brown cysts known from modern sediments include Protoperidinium americanum, Zygabikodinium lenticulatum and members of the genus Dubridinium ( Loeblich and Loeblich, 1970, Reid, 1977 and Lewis and Dodge, 1987). However, the pale brown cysts of P. americanum reflect tabulation pattern only through the shape of the archeopyle with other tabulation-like features due to gentle folding ( Lewis and Dodge, 1987). Z. lenticulatum has a tabulation pattern 3′, 2a, 7″, 3c, 5″′, 1″″ reflected by thin sutures and has an archeopyle formed by rupture along a suture between the precingular and cingular plate series ( Loeblich and Loeblich, 1970 and Bujak and Davies, 1983). This is in contrast to Cryodinium which has four apical plates and an archeopyle formed by the loss of two intercalary paraplates. Dubridinium is most unlikely to be related to Cryodinium, since it is cavate and the paratabulation is restricted to the reflection of the cingulum only ( Reid, 1977).
Cryodinium may be related to the Cretaceous ‘round brown’ genus Trithyrodinium, defined by a symmetrical 3I archeopyle and no paratabulation-reflecting sutures ( Evitt, 1985). However, this is in contrast to the 2I archeopyle and the paratabulation-reflecting sutures of Cryodinium. Therefore, specimens of Cryodinium are the first ‘round brown’ cysts with a fully reflected paratabulation on the epicyst and hypocyst and a 2I archeopyle to be found in modern sediments"
[Cryodinium, Esper and Zonneveld, 2001, p. 36–37.
This name was also proposed by Esper and Zonneveld (2002, p.201–202).
Type species: Cryodinium meridianum, Esper and Zonneveld, 2001 (pl.3, figs.1–3)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Esper and Zonneveld, 2001]:
Diagnosis:
Sphaeroidal protoperidinioid cysts with an intercalary archeopyle formed by the loss of the two paraplates 1a and 2a. Surface smooth or granular to scabrate and brown in colour. Single layered wall with low sutures reflecting a peridinioid tabulation pattern of 4′, 3a, 7″, 3c, 5′″, 2″″.
Discussion:
Spheroidal, brown cysts with smooth or slightly granulated single or double layered walls are known to be produced by dinoflagellates of the genus Protoperidinium, which is defined by the tabulation of 4′, 2-3a, 6-7″, 3c, 5″′, 2″″ plus a transitional cingular-sulcal plate (Balech, 1974). Cryodinium gen. nov. fulfills these criteria, but as its cyst–theca relation is presently unknown, we decided to erect a new fossil genus (see later discussion on Cryodinium meridianum gen. nov. sp. nov.) Some modern ‘round brown’ cyst species reflect a peridinioid tabulation pattern as evidenced by the shapes of their hexagonal archeopyles, including cysts of Protoperidinium avelanum and Protoperidinium conicoides ( Balech, 1974). However, they are clearly distinguishable from cysts of Cryodinium by their lack of sutures that reflect a paratabulation. This is also the case for the species of Brigantedinium, which is a fossil genus of round, brown cysts related to Protoperidinium species. Brigantedinium species as well reflect no paratabulation pattern besides the archeopyle ( Reid, 1977). Other paratabulated round brown cysts known from modern sediments include Protoperidinium americanum, Zygabikodinium lenticulatum and members of the genus Dubridinium ( Loeblich and Loeblich, 1970, Reid, 1977 and Lewis and Dodge, 1987). However, the pale brown cysts of P. americanum reflect tabulation pattern only through the shape of the archeopyle with other tabulation-like features due to gentle folding ( Lewis and Dodge, 1987). Z. lenticulatum has a tabulation pattern 3′, 2a, 7″, 3c, 5″′, 1″″ reflected by thin sutures and has an archeopyle formed by rupture along a suture between the precingular and cingular plate series ( Loeblich and Loeblich, 1970 and Bujak and Davies, 1983). This is in contrast to Cryodinium which has four apical plates and an archeopyle formed by the loss of two intercalary paraplates. Dubridinium is most unlikely to be related to Cryodinium, since it is cavate and the paratabulation is restricted to the reflection of the cingulum only ( Reid, 1977).
Cryodinium may be related to the Cretaceous ‘round brown’ genus Trithyrodinium, defined by a symmetrical 3I archeopyle and no paratabulation-reflecting sutures ( Evitt, 1985). However, this is in contrast to the 2I archeopyle and the paratabulation-reflecting sutures of Cryodinium. Therefore, specimens of Cryodinium are the first ‘round brown’ cysts with a fully reflected paratabulation on the epicyst and hypocyst and a 2I archeopyle to be found in modern sediments"