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Muiradinium
From Williams et al., 2017:
[Muiradinium, Harland and Sarjeant, 1970, p. 225
Type species: originally as Gymnodinium dorsispirale, Churchill and Sarjeant, 1962 (pl.1, fig.18; text-fig.2)] ; Muiradinium dorsispirale, Harland and Sarjeant, 1970
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Original description: [Harland and Sarjenat, 1970]:
Diagnosis:
Proximate dinoflagellate cyst, with a thin wall possibly composed of a single layer: no inner body is present. Ambitus diamond to spindle-shaped (varying with aspect), modified by the presence of nipple-like prominences at apex and/or antapex. Surface unornamented or with faint granulations or punctations. Cingulum prominent, marked by a pronounced groove: sulcus very poorly marked. A suggestion of tabulation, by faint lines on the surface, may be present or absent: but a full tabulation is not determinable. Archaeopyle intercalary, small and placed very close to the apex.
Affinities:
This new genus differs from the genus Deflandrea in the lack of an inner body: from the cysts of Peridinium limbatum (recently re-studied by Evitt and Wall, 1968) in the character of its archaeopyle: from the cyst here described as ? Peridinium diamantum in the smaller size of the archaeopyle and the absence of a recognizable Peridinium-type tabulation: and from the genus Dinogymnium Evitt, Clarke and Verdier 1967 in the character of the archaeopyle and the absence of any system of mural pores.
The identity of the dinoflagellate which formed this cyst remains a matter for speculation. The outline resembles that of some members of the Order Gymnodiniales, four genera of which Amphidinium, Gymnodinium, Gyrodinium and Massartial are known from fresh water: but the shape of the archaeopyle and the occasional faint suggestions of a tabulation favour the possibility that this is the cyst of a freshwater member of the Family Peridiniaceae and probably of a species of the genus Peridinium (much the most abundant genus in fresh waters). This genus does contain biconical species: recent studies have suggested that, though its motile morphology is relatively constant, the morphology of its cysts is very variable and a future division of the genus into a number of new genera, on the basis of knowledge of the whole life cycle, seems probable.
[Muiradinium, Harland and Sarjeant, 1970, p. 225
Type species: originally as Gymnodinium dorsispirale, Churchill and Sarjeant, 1962 (pl.1, fig.18; text-fig.2)] ; Muiradinium dorsispirale, Harland and Sarjeant, 1970
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Harland and Sarjenat, 1970]:
Diagnosis:
Proximate dinoflagellate cyst, with a thin wall possibly composed of a single layer: no inner body is present. Ambitus diamond to spindle-shaped (varying with aspect), modified by the presence of nipple-like prominences at apex and/or antapex. Surface unornamented or with faint granulations or punctations. Cingulum prominent, marked by a pronounced groove: sulcus very poorly marked. A suggestion of tabulation, by faint lines on the surface, may be present or absent: but a full tabulation is not determinable. Archaeopyle intercalary, small and placed very close to the apex.
Affinities:
This new genus differs from the genus Deflandrea in the lack of an inner body: from the cysts of Peridinium limbatum (recently re-studied by Evitt and Wall, 1968) in the character of its archaeopyle: from the cyst here described as ? Peridinium diamantum in the smaller size of the archaeopyle and the absence of a recognizable Peridinium-type tabulation: and from the genus Dinogymnium Evitt, Clarke and Verdier 1967 in the character of the archaeopyle and the absence of any system of mural pores.
The identity of the dinoflagellate which formed this cyst remains a matter for speculation. The outline resembles that of some members of the Order Gymnodiniales, four genera of which Amphidinium, Gymnodinium, Gyrodinium and Massartial are known from fresh water: but the shape of the archaeopyle and the occasional faint suggestions of a tabulation favour the possibility that this is the cyst of a freshwater member of the Family Peridiniaceae and probably of a species of the genus Peridinium (much the most abundant genus in fresh waters). This genus does contain biconical species: recent studies have suggested that, though its motile morphology is relatively constant, the morphology of its cysts is very variable and a future division of the genus into a number of new genera, on the basis of knowledge of the whole life cycle, seems probable.