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Meiourogonyaulax borealis
Meiourogonyaulax borealis Sarjeant, 1980b, p.123–124.
Holotype: Sarjeant, 1972, pl.5, fig.3; text-fig.5, as Meiourogonyaulax decapitata. Originally (and now) Meiourogonyaulax, subsequently Lithodinia. This species is here retained in Meiourogonyaulax following the retention of the genus by Riding and Helby (2001d, p.81,83). Taxonomic junior synonym: Lithodinia arktika, according to Riley and Fenton (1982, p.200).
Age: late Bathonian.
Diagnosis: Sarjeant 1980, p. 123-124: Meiourogonyaulax borealis
Cyst proximate, broadly ovoidal, with apex typically lost in archaeopyle formation. Crests of moderate height, commonly finely or coarsely perforate and sometimes having the appearance of lines of spines linked distally by a trabecula. Paratabulation ?",6",6 c,6"",1 p,1 pv,1"". Paraplate 1"" is quite large and separated from the antapex by a posterior intercalary paraplate (1 p) of slightly smaller size: both paraplates are almost quadrate in shape. Parasulcus moderately broad, widening slightly towards the posterior and separated from the antapex by a short, broad posterior ventral paraplate. Paracingulum of moderate breadth, weakly laevorotatory.
Dimensions. Length (apex lacking) 72 µm, breadth" 71.5, µm, height of crests c. 4 µm Observed range: length (apex lacking) 62-72 µm (mean 63.14 µm), breadth 57- 71.5 µm (mean 65.07 µm). Material. 17 specimens of which only seven were satisfactory for measurement.
Description: Sarjeant 1980, p. 123-124: Meiourogonyaulax borealis
The crests are very variable in heightl with an undulose "crest-line" Because of their prominencel the cysts have a polygonal appearance in some orientations. The surface appears under low magnification to be granular; under higher magnificationl howeverl it has the appearance of a irregularl fine-meshed net. This may well be a preservational effect; certainly it cannot presently be considered a diagnostic character. Because of this ornamentationl I was unable to decide whether sulcal paraplates were developed. The paracingulum is quite weakly laevorotatory, its two ends differing in anteroposterior position by less than its width.
Remarks: Sarjeant 1980, p. 123-124
Meiourogonyaulax borealis differs from M.decapitata, as here emended, in its more broadly ovoidal shape, lower crests, shorter and broader posterior ventral paraplate, smaller posterior intercalary paraplate (separating only paraplate 1"" from the antapex) and lack of a second small paraplate (2 p) to the right of the posterior part of the parasulcus. Its parasulcus is less broad and its paracingulum less markedly laevorotatory. Of other species of Meiourogonyaulaxl the mostsimilar is M. callomonii SARJEANTI 1972; howeverl the two species differ markedly in ventral paratabulation and the latter has a much narrowerl more strongly spiral paracingulum.
The specimen illustrated as Meiourogonyaulax decapitata by HERNGREEN and DE BOERI from the Lower-Middle Dogger of the Netherlandsl appears from their illustration (no description is included) to be referable to Meiourogonyaulax borealis.
synonyms:
1972 Meiourogonyaulax decapitata (W. WETZEL) SARJEANT, 29--31, pl. 5 fig. 3, text-fig. 5
1974 Meiourogonyaulax decapitata (W. WE.) SARJ . HERNGREEN and DE BOER,357, pl.6 fig.6, tab 6.
Holotype: Sarjeant, 1972, pl.5, fig.3; text-fig.5, as Meiourogonyaulax decapitata. Originally (and now) Meiourogonyaulax, subsequently Lithodinia. This species is here retained in Meiourogonyaulax following the retention of the genus by Riding and Helby (2001d, p.81,83). Taxonomic junior synonym: Lithodinia arktika, according to Riley and Fenton (1982, p.200).
Age: late Bathonian.
Diagnosis: Sarjeant 1980, p. 123-124: Meiourogonyaulax borealis
Cyst proximate, broadly ovoidal, with apex typically lost in archaeopyle formation. Crests of moderate height, commonly finely or coarsely perforate and sometimes having the appearance of lines of spines linked distally by a trabecula. Paratabulation ?",6",6 c,6"",1 p,1 pv,1"". Paraplate 1"" is quite large and separated from the antapex by a posterior intercalary paraplate (1 p) of slightly smaller size: both paraplates are almost quadrate in shape. Parasulcus moderately broad, widening slightly towards the posterior and separated from the antapex by a short, broad posterior ventral paraplate. Paracingulum of moderate breadth, weakly laevorotatory.
Dimensions. Length (apex lacking) 72 µm, breadth" 71.5, µm, height of crests c. 4 µm Observed range: length (apex lacking) 62-72 µm (mean 63.14 µm), breadth 57- 71.5 µm (mean 65.07 µm). Material. 17 specimens of which only seven were satisfactory for measurement.
Description: Sarjeant 1980, p. 123-124: Meiourogonyaulax borealis
The crests are very variable in heightl with an undulose "crest-line" Because of their prominencel the cysts have a polygonal appearance in some orientations. The surface appears under low magnification to be granular; under higher magnificationl howeverl it has the appearance of a irregularl fine-meshed net. This may well be a preservational effect; certainly it cannot presently be considered a diagnostic character. Because of this ornamentationl I was unable to decide whether sulcal paraplates were developed. The paracingulum is quite weakly laevorotatory, its two ends differing in anteroposterior position by less than its width.
Remarks: Sarjeant 1980, p. 123-124
Meiourogonyaulax borealis differs from M.decapitata, as here emended, in its more broadly ovoidal shape, lower crests, shorter and broader posterior ventral paraplate, smaller posterior intercalary paraplate (separating only paraplate 1"" from the antapex) and lack of a second small paraplate (2 p) to the right of the posterior part of the parasulcus. Its parasulcus is less broad and its paracingulum less markedly laevorotatory. Of other species of Meiourogonyaulaxl the mostsimilar is M. callomonii SARJEANTI 1972; howeverl the two species differ markedly in ventral paratabulation and the latter has a much narrowerl more strongly spiral paracingulum.
The specimen illustrated as Meiourogonyaulax decapitata by HERNGREEN and DE BOERI from the Lower-Middle Dogger of the Netherlandsl appears from their illustration (no description is included) to be referable to Meiourogonyaulax borealis.
synonyms:
1972 Meiourogonyaulax decapitata (W. WETZEL) SARJEANT, 29--31, pl. 5 fig. 3, text-fig. 5
1974 Meiourogonyaulax decapitata (W. WE.) SARJ . HERNGREEN and DE BOER,357, pl.6 fig.6, tab 6.