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Diconodinium wilsonii
Diconodinium wilsonii Aurisano, 1984
Taxonomic junior synonym: Biconidinium parvum (name not validly published), according to Slimani (2001a, p.192). See also Diconodinium parvum.
Holotype: Aurisano, 1984, figs.4A-C
Age: Late Campanian-latest Maastrichtian.
Original description (Aurisano, 1984):
Type locality and stratum: 904 well, Delaware, USA, 26.82 meters depth, early Meastrichtian
Diagnosis: Apical horn has very thick bolders and appears solid or almost solid; solid antapical spinelike horn lies close to longitudinal axis. Autocyst surface finely granulate with linear, longitudinal folds in cyst wall.
Derivation of name: Named in honor of Greame J. Wilson.
Description: A proximate dinoflagellate cyst with a fusiform, biconical outline and two horns – one apical, the other antapical. The apical horn has very thick borders and appears solid or almost solid. The antapical horn is close to the longitudinal axis and is a solid, spinelike projection. The cyst body appears to be unilayered, although in the apical region a case could be made for separation of wall layers just below the apical horn. The surface of the autocyst is covered with fin, nontabularly arranged granules that are less than 1 µm in diameter. Paracingulum and parasulcus are indicated by faint or weakely developed ridges. Paracingulum is continuous and only slightly laevorotatory. Parasulcus is comparatively wide. Paratabulation is incompletely expressed by intercalary archeopyle. Archeopyle formula appears to be I (2a only); its outline is a standard hexa, which has been observed in one specimen only.
Dimensions: (on numerous specimens). Maximum length 33-46 µm; maximum width 24-30 µm.
Remarks: Aurisano and Habib (1976) originally identified specimens of Diconodinium wilsonii from the Thoms River core as D. firmum Harland (1973). Subsequently, D. firmum was transferred to Laciniadinium by Morgan (1977) on the basis of its combination archeopyle, type tI3Pa. The operculum has a flaplike appearance, a feature which has not been observed ion de specimens from New Jersey and Delaware. The type specimen has a standard hexa, type I (2a only) archeopyle. On this basis, the specimens from this study are placed in Diconodinium and given the specific name wilsonii as they are similar to specimens of D. parvum described by Wilson in an unpublished thesis (1974). Diconodinium wilsonii differs from D. arcticum, Manum and Cookson, 1964. The shape of D. arcticum is generally inflated with convex margins. In addition, the apical protrusion of D. arctucum is wider and stouter in appearance, its walls thinner, and its granules less densely distributed than those of D. wilsonii. D. wilsonii differs from D. glabrum Eisenack and Cookson, 1960 in that the epicyst and hypocyst are approximately aqual in length, while the epicyst is generally longer in D. glabrum. Also, D. glabrum has distinct apical and antapical pericoels and its antapical horns is not spinelike. Specimens identified as D. rhombiformis Vozzhennikova, 1967 by May (1980) appear to be similar to those of D. wilsonii. The type of D. rhombiformis figured by Vozzhennikova (1967, p. 74, Pl. 7, fig. 3) appears to be more elongate than D. wilsonii. Also, the apical and antapical horns are characterized by a microreticulate ornamentation which is not present in D. wilsonii.
Occurrence. Diconodinium wilsonii from New Jersey and Dalaware samples first appears in the uppermost part of the Bolivinoides decorates zones, and disappears in the uppermost part of the Abathomphalus mayaroensis and B. draco zones (late Campanian to latest Meastrichtian).
Taxonomic junior synonym: Biconidinium parvum (name not validly published), according to Slimani (2001a, p.192). See also Diconodinium parvum.
Holotype: Aurisano, 1984, figs.4A-C
Age: Late Campanian-latest Maastrichtian.
Original description (Aurisano, 1984):
Type locality and stratum: 904 well, Delaware, USA, 26.82 meters depth, early Meastrichtian
Diagnosis: Apical horn has very thick bolders and appears solid or almost solid; solid antapical spinelike horn lies close to longitudinal axis. Autocyst surface finely granulate with linear, longitudinal folds in cyst wall.
Derivation of name: Named in honor of Greame J. Wilson.
Description: A proximate dinoflagellate cyst with a fusiform, biconical outline and two horns – one apical, the other antapical. The apical horn has very thick borders and appears solid or almost solid. The antapical horn is close to the longitudinal axis and is a solid, spinelike projection. The cyst body appears to be unilayered, although in the apical region a case could be made for separation of wall layers just below the apical horn. The surface of the autocyst is covered with fin, nontabularly arranged granules that are less than 1 µm in diameter. Paracingulum and parasulcus are indicated by faint or weakely developed ridges. Paracingulum is continuous and only slightly laevorotatory. Parasulcus is comparatively wide. Paratabulation is incompletely expressed by intercalary archeopyle. Archeopyle formula appears to be I (2a only); its outline is a standard hexa, which has been observed in one specimen only.
Dimensions: (on numerous specimens). Maximum length 33-46 µm; maximum width 24-30 µm.
Remarks: Aurisano and Habib (1976) originally identified specimens of Diconodinium wilsonii from the Thoms River core as D. firmum Harland (1973). Subsequently, D. firmum was transferred to Laciniadinium by Morgan (1977) on the basis of its combination archeopyle, type tI3Pa. The operculum has a flaplike appearance, a feature which has not been observed ion de specimens from New Jersey and Delaware. The type specimen has a standard hexa, type I (2a only) archeopyle. On this basis, the specimens from this study are placed in Diconodinium and given the specific name wilsonii as they are similar to specimens of D. parvum described by Wilson in an unpublished thesis (1974). Diconodinium wilsonii differs from D. arcticum, Manum and Cookson, 1964. The shape of D. arcticum is generally inflated with convex margins. In addition, the apical protrusion of D. arctucum is wider and stouter in appearance, its walls thinner, and its granules less densely distributed than those of D. wilsonii. D. wilsonii differs from D. glabrum Eisenack and Cookson, 1960 in that the epicyst and hypocyst are approximately aqual in length, while the epicyst is generally longer in D. glabrum. Also, D. glabrum has distinct apical and antapical pericoels and its antapical horns is not spinelike. Specimens identified as D. rhombiformis Vozzhennikova, 1967 by May (1980) appear to be similar to those of D. wilsonii. The type of D. rhombiformis figured by Vozzhennikova (1967, p. 74, Pl. 7, fig. 3) appears to be more elongate than D. wilsonii. Also, the apical and antapical horns are characterized by a microreticulate ornamentation which is not present in D. wilsonii.
Occurrence. Diconodinium wilsonii from New Jersey and Dalaware samples first appears in the uppermost part of the Bolivinoides decorates zones, and disappears in the uppermost part of the Abathomphalus mayaroensis and B. draco zones (late Campanian to latest Meastrichtian).