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Desotodinium
From Williams et al., 2017:
[Desotodinium, De Schepper et al., 2004, p. 431, 433
Type species: Desotodinium wrennii, De Schepper et al., 2004 (fig.7, nos.1–6)]
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Original description: [De Schepper et al., 2004]:
Diagnosis:
Discoidal, polar-compressed, proximate, smooth to weakly ornamented cysts, whose compound polyplacoid hypocystal archeopyle is formed of several, but not all, plates of the postcingular series, and one or more fundital plates. Tabulation otherwise weakly or not expressed. Thin equatorial flange sometimes present.
Discussion:
Some goniodomacean genera show plate multiplication, whereas others do not. Within individual goniodomacean genera, plate multiplication is variable: for example, the pyrodinioidean genus Capisocysta contains both a species with a single antapical plate (Capisocysta lata Head, 1998b) and a species with two antapical plates (Capisocysta lyellii Head, 1998b). Moreover, even within the helgolandinioidean species Pyrophacus steinii (Schiller, 1935) Wall and Dale, 1971 (whose cyst-based name is Tuberculodinium vancampoae) the degree of plate multiplication is highly variable on the hypotheca. Accordingly, the new genus Desotodinium is circumscribed to accommodate species with a single antapical plate as well as those with multiple antapical plates. It is also a feature of some goniodomaceans that more plates may be involved on the hyposome of the motile stage than may be reflected in the cyst. For example, tabulation on the cysts of Pyrophacus horologium (Wall and Dale, 1971, fig. 4d– g) incompletely reflects tabulation on the hypotheca (Wall and Dale, 1971, fig. 1a). The same may be true of the new genus Desotodinium.
Affinities:
Capisocysta Warny and Wrenn, 1997 emend. Head, 1998b differs from Desotodinium in having a more complete dissociation of the hypocyst into constituent plates, including all postcingular plates. All known species of Capisocysta have a spheroidal rather than discoidal shape, and an equatorial flange is never present. Tuberculodinium Wall, 1967 has numerous processes, which are absent from Desotodinium. Archeopyle formation in Geonettia de Verteuil and Norris, 1996 involves extensive dissociation of plates on both epicyst and hypocyst.
Biological affinity: Assignment to the subfamily Helgolandinioideae within the Goniodomaceae is based on the following evidence. The archeopyle of Desotodinium is restricted to the hypocyst, a rare feature in dinoflagellate cysts. Within the Gonyaulacales, the only previous unambiguous example of such an archeopyle occurs in the goniodomacean genus Capisocysta (Head, 1998b). A general characteristic of helgolandinioideans is plate multiplication (Fensome et al., 1993), which is developed extensively on Tuberculodinium vancampoae (Rossignol, 1962) Wall, 1967. Plate multiplication on Desotodinium is recognized on the type species by the consistent presence of two antapical plates, originating from one ancestral plate. Furthermore, the type of Desotodinium bears strong similarity to the cyst of the theca-defined helgolandinioidean species Pyrophacus horologium von Stein, 1883. See under Desotodinium wrennii for discussion.
[Desotodinium, De Schepper et al., 2004, p. 431, 433
Type species: Desotodinium wrennii, De Schepper et al., 2004 (fig.7, nos.1–6)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [De Schepper et al., 2004]:
Diagnosis:
Discoidal, polar-compressed, proximate, smooth to weakly ornamented cysts, whose compound polyplacoid hypocystal archeopyle is formed of several, but not all, plates of the postcingular series, and one or more fundital plates. Tabulation otherwise weakly or not expressed. Thin equatorial flange sometimes present.
Discussion:
Some goniodomacean genera show plate multiplication, whereas others do not. Within individual goniodomacean genera, plate multiplication is variable: for example, the pyrodinioidean genus Capisocysta contains both a species with a single antapical plate (Capisocysta lata Head, 1998b) and a species with two antapical plates (Capisocysta lyellii Head, 1998b). Moreover, even within the helgolandinioidean species Pyrophacus steinii (Schiller, 1935) Wall and Dale, 1971 (whose cyst-based name is Tuberculodinium vancampoae) the degree of plate multiplication is highly variable on the hypotheca. Accordingly, the new genus Desotodinium is circumscribed to accommodate species with a single antapical plate as well as those with multiple antapical plates. It is also a feature of some goniodomaceans that more plates may be involved on the hyposome of the motile stage than may be reflected in the cyst. For example, tabulation on the cysts of Pyrophacus horologium (Wall and Dale, 1971, fig. 4d– g) incompletely reflects tabulation on the hypotheca (Wall and Dale, 1971, fig. 1a). The same may be true of the new genus Desotodinium.
Affinities:
Capisocysta Warny and Wrenn, 1997 emend. Head, 1998b differs from Desotodinium in having a more complete dissociation of the hypocyst into constituent plates, including all postcingular plates. All known species of Capisocysta have a spheroidal rather than discoidal shape, and an equatorial flange is never present. Tuberculodinium Wall, 1967 has numerous processes, which are absent from Desotodinium. Archeopyle formation in Geonettia de Verteuil and Norris, 1996 involves extensive dissociation of plates on both epicyst and hypocyst.
Biological affinity: Assignment to the subfamily Helgolandinioideae within the Goniodomaceae is based on the following evidence. The archeopyle of Desotodinium is restricted to the hypocyst, a rare feature in dinoflagellate cysts. Within the Gonyaulacales, the only previous unambiguous example of such an archeopyle occurs in the goniodomacean genus Capisocysta (Head, 1998b). A general characteristic of helgolandinioideans is plate multiplication (Fensome et al., 1993), which is developed extensively on Tuberculodinium vancampoae (Rossignol, 1962) Wall, 1967. Plate multiplication on Desotodinium is recognized on the type species by the consistent presence of two antapical plates, originating from one ancestral plate. Furthermore, the type of Desotodinium bears strong similarity to the cyst of the theca-defined helgolandinioidean species Pyrophacus horologium von Stein, 1883. See under Desotodinium wrennii for discussion.