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Quinquecuspis pentagona
Quinquecuspis pentagona sp. nov., Uddandam et al. 2020
Holotype: Plate III; 1-3, Uddandam et al. 2020
Type locality: Recent sediments (0-1 cm) north-western Bay of Bengal
Original description: Uddandam et al. 2020:
Diagnosis:
A large, proximate, pentagonal cyst compressed dorsoventrally. Epicysts smaller than hypocyst, conical with slightly concave to straight sides in dorsoventral view with
pointed, prominently thickened polar horns. Cyst wall consists of autophragm which is brown in colour. Autophragm consists discontinuous longitudinal striations (~10-30 μm) on epicysts and hypocyst. Epicyst and hypocyst are separated by two rows of cingular ridges which are finely denticulated. Sulcul depression is prominent. Antapical concavity is small. Archeopyle simple, mid-dorsal intercalary 2a type.
Description:
Cysts large in size (130-160 μm), pentagonal in outline with strong dorsoventral compression. Cysts consist of two antapical and one apical horn with sharply distally
pointed thickened tips. Lateral horns or protrusions are absent.
Autophragm: brown, of moderate thickness and bears prominent, smooth, discontinuous, non-tabular longitudinal striations, 10-30 μm in length.
Hypocyst: slightly larger than the epicyst.
Epicyst: conical with straight to very weakly concave sides, and hypocyst is trapezoidal with straight to concave sides. The antapical concavity is small prominent and
the paired antapical horns are separated apart from the midline by a prominent antapical depression.
Paratabulation: expressed in the form of archaeopyle and cingulum.
Archeopyle: large, simple intercalary, mid-dorsal in position involving anterior intercalary paraplate which is hexagonal (isodeltaform) in shape with a broad posterior and shorter anterior margin.
Cingulum: prominent and is bordered by two denticulate sutural ridges, planar and indented.
Sulcus: deeply indented.
Dimensions:
Cyst length 130-160 μm. Cyst width: 130-135 μm. Epicyst, 64-75 μm and Hypocyst, 75-85 μm.
20 specimens measured.
Remarks:
This species is very fragile and found often folded and degraded where other species of protoperidinioids are well preserved.
Affinities/Comparison:
It differs from Stelladinium in having no extended lateral horns. It differs from the Lejeunecysta in having a clear deep ventral sulcus and antapical depression which separate the antapical horns. It differs from Quinquecuspis concreta in being bigger in size with a large archeopyle and clear expression of cingulum represented by two denticulate ridges. When apical-antapically compressed, specimens are apparently similar to Selenopemphix nephroides, but these cysts are differentiated by their larger size and denticulate cingulum ridges. It differs from Lejeunecysta paratenella in having large ambitus and pentagonal shape. Quinquecuspis pentagona differs from L. longistriata in having bigger size and distinct cingulum.
Holotype: Plate III; 1-3, Uddandam et al. 2020
Type locality: Recent sediments (0-1 cm) north-western Bay of Bengal
Original description: Uddandam et al. 2020:
Diagnosis:
A large, proximate, pentagonal cyst compressed dorsoventrally. Epicysts smaller than hypocyst, conical with slightly concave to straight sides in dorsoventral view with
pointed, prominently thickened polar horns. Cyst wall consists of autophragm which is brown in colour. Autophragm consists discontinuous longitudinal striations (~10-30 μm) on epicysts and hypocyst. Epicyst and hypocyst are separated by two rows of cingular ridges which are finely denticulated. Sulcul depression is prominent. Antapical concavity is small. Archeopyle simple, mid-dorsal intercalary 2a type.
Description:
Cysts large in size (130-160 μm), pentagonal in outline with strong dorsoventral compression. Cysts consist of two antapical and one apical horn with sharply distally
pointed thickened tips. Lateral horns or protrusions are absent.
Autophragm: brown, of moderate thickness and bears prominent, smooth, discontinuous, non-tabular longitudinal striations, 10-30 μm in length.
Hypocyst: slightly larger than the epicyst.
Epicyst: conical with straight to very weakly concave sides, and hypocyst is trapezoidal with straight to concave sides. The antapical concavity is small prominent and
the paired antapical horns are separated apart from the midline by a prominent antapical depression.
Paratabulation: expressed in the form of archaeopyle and cingulum.
Archeopyle: large, simple intercalary, mid-dorsal in position involving anterior intercalary paraplate which is hexagonal (isodeltaform) in shape with a broad posterior and shorter anterior margin.
Cingulum: prominent and is bordered by two denticulate sutural ridges, planar and indented.
Sulcus: deeply indented.
Dimensions:
Cyst length 130-160 μm. Cyst width: 130-135 μm. Epicyst, 64-75 μm and Hypocyst, 75-85 μm.
20 specimens measured.
Remarks:
This species is very fragile and found often folded and degraded where other species of protoperidinioids are well preserved.
Affinities/Comparison:
It differs from Stelladinium in having no extended lateral horns. It differs from the Lejeunecysta in having a clear deep ventral sulcus and antapical depression which separate the antapical horns. It differs from Quinquecuspis concreta in being bigger in size with a large archeopyle and clear expression of cingulum represented by two denticulate ridges. When apical-antapically compressed, specimens are apparently similar to Selenopemphix nephroides, but these cysts are differentiated by their larger size and denticulate cingulum ridges. It differs from Lejeunecysta paratenella in having large ambitus and pentagonal shape. Quinquecuspis pentagona differs from L. longistriata in having bigger size and distinct cingulum.