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Membranigonyaulax
From Fensome et al., 2019:
Membranigonyaulax, Slimani, 1994, p.19.
Type: Slimani, 1994, pl.2, figs.17–18; text-figs.5A–B, as Membranigonyaulax wilsonii.
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Original description: [Slimani, 1994]: (Translation: LPP):
Diagnosis:
Cyst proximate, holocavate, subspheroidal to subpolygonal; endocyst with appressed endophragm and periphragm. Ectophragm thin, delicate, smooth or punctate and separated from the endocyst by a very reduced to large ectocoel; it is supported by variable parasutural and intratabular structures. The parasutural structures may be low crests and/or processes or protruding septa; their height varies between 1/15 and 2/3 of the total cyst diameter. The intratabular supporting structures may be expressed by one single central process per plate and/or secondary septa or numerous short, more or less closely specced pillars, or by secondary crests, vermiculae and granulae, which are more or less strongly interconnected forming or not forming a reticulum.
The paratabulation is gonyaulacoid, in accordance with the following formula: 4`, 6``, 6c, 5```, 1pv, 1p, 1````, xs. The hypocystal paraplates have a quinqueform gonyaulacoid arrangement; the parasulcus is not subdivided.
The paracingulum is subdivided and often lacks intratabular structures.
The archaeopyle is apical, type (4A), with a hexagonal margin and with a deep sulcal notch ventrally; the operculum is free or attached.
The size is small to intermediate, 30-70 µm.
Affinities:
Membranigonyaulax differs from all dinocyst genera described until now by the presence of the following characteristics: the presence of an ectocoel, parasutural and intratabular structures supporting an ectophragm, and apical type (4A) archaeopyle with a deep sulcal notch, a quinqueform gonyaulacoid paratabulation, and the absence of horns.
Lithodinia Eisenack, 1935 emend. Gocht, 1975, has an autophragma and a type 4A apical archaeopyle and its parasutural and intratabular structures are not connected distally.
Meiourogonyaulax Sarjeant, 1966, also presents a 4A type apical archaeopyle, but it has an autophragm, its parasutural and intratabular structures do not support an ectophragm.
Ambonosphaera Fensome, 1979, also presents a 4A type archaeopyle, but shows a pericoel between periphragm and endophragm, which are not interconnected by structures, the parasutural relief is located on the periphragm.
Senoniasphaera Clarke and Verdier, 1967, primarily differs from the present genus in the presence of horns.
Microdinium Cookson and Eisenack, 1960 emend. Sarjeant, 1966 emend. Stover and Evitt, 1978, presents a partiform gonyaulacoid paratabulation and a much smaller, apical-intercalary, (tAtI)a type archaeopyle.
Membranigonyaulax, Slimani, 1994, p.19.
Type: Slimani, 1994, pl.2, figs.17–18; text-figs.5A–B, as Membranigonyaulax wilsonii.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Slimani, 1994]: (Translation: LPP):
Diagnosis:
Cyst proximate, holocavate, subspheroidal to subpolygonal; endocyst with appressed endophragm and periphragm. Ectophragm thin, delicate, smooth or punctate and separated from the endocyst by a very reduced to large ectocoel; it is supported by variable parasutural and intratabular structures. The parasutural structures may be low crests and/or processes or protruding septa; their height varies between 1/15 and 2/3 of the total cyst diameter. The intratabular supporting structures may be expressed by one single central process per plate and/or secondary septa or numerous short, more or less closely specced pillars, or by secondary crests, vermiculae and granulae, which are more or less strongly interconnected forming or not forming a reticulum.
The paratabulation is gonyaulacoid, in accordance with the following formula: 4`, 6``, 6c, 5```, 1pv, 1p, 1````, xs. The hypocystal paraplates have a quinqueform gonyaulacoid arrangement; the parasulcus is not subdivided.
The paracingulum is subdivided and often lacks intratabular structures.
The archaeopyle is apical, type (4A), with a hexagonal margin and with a deep sulcal notch ventrally; the operculum is free or attached.
The size is small to intermediate, 30-70 µm.
Affinities:
Membranigonyaulax differs from all dinocyst genera described until now by the presence of the following characteristics: the presence of an ectocoel, parasutural and intratabular structures supporting an ectophragm, and apical type (4A) archaeopyle with a deep sulcal notch, a quinqueform gonyaulacoid paratabulation, and the absence of horns.
Lithodinia Eisenack, 1935 emend. Gocht, 1975, has an autophragma and a type 4A apical archaeopyle and its parasutural and intratabular structures are not connected distally.
Meiourogonyaulax Sarjeant, 1966, also presents a 4A type apical archaeopyle, but it has an autophragm, its parasutural and intratabular structures do not support an ectophragm.
Ambonosphaera Fensome, 1979, also presents a 4A type archaeopyle, but shows a pericoel between periphragm and endophragm, which are not interconnected by structures, the parasutural relief is located on the periphragm.
Senoniasphaera Clarke and Verdier, 1967, primarily differs from the present genus in the presence of horns.
Microdinium Cookson and Eisenack, 1960 emend. Sarjeant, 1966 emend. Stover and Evitt, 1978, presents a partiform gonyaulacoid paratabulation and a much smaller, apical-intercalary, (tAtI)a type archaeopyle.