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Spinidinium pentagonum
Spinidinium pentagonum Kurita, 2004, p 36,38,40,42, pl.1, figs.1–16.
Holotype: Kurita, 2004, pl.1, figs.1–4.
Age: late middle to ?late Eocene.
Original description (Kurita, 2004)
Holotype: Sample KR904-011, slide dn-5, 95.5x12.0 (Plate 1, figs. 1-4)
Paratypes: Sample KR904-011, slide dn-4, 97.1x15.8 (Plate 1, figs. 5-7)
Sample KR904-011, slide dn-5, 102.1x12.9 (Plate 1, figs. 9-11)
Repository: Stored in the palynological collection at the Department of Geology, Faculty of Science, Niigata University.
Type locality: KR904-011, Futamata-sawa tributary of the Chikubetsu River, Haboro Town, Rumoi Province, Hokkaido, Japan; latitude 44º23'57"N, longitude 141º54'15"E.
Type stratum: Lower part of the Sankebetsu Formation (Matsuno and Kino 1960), upper Middle to Upper Eocene (Kurita et al. 1992).
Derivation of name: pentagonus-Latin, referring to the pentagonal ambital shape.
Diagnosis: A species of the genus Spinidinium with pentagonal to rounded pentagonal body and with triangular epicyst. Periphragm with numerous short spines which are usually acuminate, rarely capitate, and in penitabular spine arrangement. Apical pericoel generally large. Large, intercalary 2a archeopyle, Type I@, which is hexagonal and isodeltaform. Operculum always in place, adnate posteriorly.
Description: Proximate cyst, dorso-ventrally compressed peridinioid, cornucavate, pentagonal to rounded pentagonal, with triangular epicyst. Small or reduced apical horn present. Two antapical horns present or absent. When present, right antapical horn strongly reduced. On horns, relatively long, sometimes slightly membranous, spines present. Periphragm thin, generally smooth or laevigate, with numerous short spines which are usually acuminate, rarely capitate. Density of the spines on pericyst rather consistent. Penitabular spine arrangement
present typically around archeopyle and on operculum. In other areas of pericyst, penitabular arrangement sometimes absent or developed only partially. Paracingulum, being indicated by two ridges with row of spines, relatively wide and generally well delineated in cyst ambitus. Displacement of paracingulum not clear, probably not prominent. Parasulcus indicated by lackof paracingular rows of spines or ridges, and by shallow depression of the cyst in the ventral area, widening toward antapex. Endocyst rounded hexagonal with thin, smooth endophragm without ornament, appressed to periphragm except beneath horns. Paratabulation indicated incompletely by paracingulum, parasulcus, archeopyle and partial penitabular arrangement of spines on pericyst. Intercalary archeopyle always discernible, derived from loss of paraplate 2a, hexagonal, isodeltaform, Type I@, relatively large. Transverse archeopyle index= 0.49-0.77, average 0.59 (15 specimens measured). Accessory
archeopyle sutures along paraplate boundaries 3"/ 4" and 4"/ 5" sometimes present. Operculum always in place, adnate posteriorly.
Dimensions: Cyst overall length 42µm-63µm (average 51µm), width 33µm-57µm (average 41µm), 137 specimens measured. Spine length up to 2µm. Apical horn length 4.3µm; larger antapical horn length up to 5µm.
Occurrence: Abundant in the basal part of the lower part of the Sankebetsu Formation, Haboro area; Bellatudinium hokkaidoanum Zone, upper Middle (to Upper?) Eocene. Records in the Kamicharo and Kiroro Formations (Upper Oligocene to Lower Miocene), Shiranuka area, are interpreted to represent reworkingObserved range in this study: upper Middle (to Upper?) Eocene.
Remarks: This new species is characterized by its rounded pentagonal body shape, large, triangular apical pericoel and large, isodeltaform hexagonal, 2a archeopyle. The cornucavate wall relationships are distinctive in most of the observed specimens. Although the spines are not always entirely penitabular, the consistent presence of penitabular spines, at least in parts of the body, and the cornucavate wall relationships confirm the generic assignment of this species to Spinidinium. Variation of the cyst shape is not profound as indicated in Plate 1, figures 1-16. Height of epicyst more or less equal to that of hypocyst. Spinidinium pentagonum sp. nov. is distinguished from otherspecies of the genus by its angular, pentagonal ambital shape. It differs from Spinidinium? tripylum sp. nov. in overall cyst shape, apical pericoel shape and archeopyle configuration. It also differs from Spinidinium essoi Cookson and Eisenack 1967in having a larger apical pericoel. Spinidinium pentagonum sp. nov. frequently occurs with Trinovantedinium boreale, which also has a peridinioid outline, type I archeopyle and a general covering of relatively short spines. However, Spinidinium pentagonum sp. nov. is cornucavate and has a large, easily discernible archeopyle.This species is dominant in the basal part of the lower part of the Sankebetsu Formation, Haboro area, central Hokkaido. This horizon probably corresponds to the basal part of the Bellatudinium hokkaidoanum Zone.
Holotype: Kurita, 2004, pl.1, figs.1–4.
Age: late middle to ?late Eocene.
Original description (Kurita, 2004)
Holotype: Sample KR904-011, slide dn-5, 95.5x12.0 (Plate 1, figs. 1-4)
Paratypes: Sample KR904-011, slide dn-4, 97.1x15.8 (Plate 1, figs. 5-7)
Sample KR904-011, slide dn-5, 102.1x12.9 (Plate 1, figs. 9-11)
Repository: Stored in the palynological collection at the Department of Geology, Faculty of Science, Niigata University.
Type locality: KR904-011, Futamata-sawa tributary of the Chikubetsu River, Haboro Town, Rumoi Province, Hokkaido, Japan; latitude 44º23'57"N, longitude 141º54'15"E.
Type stratum: Lower part of the Sankebetsu Formation (Matsuno and Kino 1960), upper Middle to Upper Eocene (Kurita et al. 1992).
Derivation of name: pentagonus-Latin, referring to the pentagonal ambital shape.
Diagnosis: A species of the genus Spinidinium with pentagonal to rounded pentagonal body and with triangular epicyst. Periphragm with numerous short spines which are usually acuminate, rarely capitate, and in penitabular spine arrangement. Apical pericoel generally large. Large, intercalary 2a archeopyle, Type I@, which is hexagonal and isodeltaform. Operculum always in place, adnate posteriorly.
Description: Proximate cyst, dorso-ventrally compressed peridinioid, cornucavate, pentagonal to rounded pentagonal, with triangular epicyst. Small or reduced apical horn present. Two antapical horns present or absent. When present, right antapical horn strongly reduced. On horns, relatively long, sometimes slightly membranous, spines present. Periphragm thin, generally smooth or laevigate, with numerous short spines which are usually acuminate, rarely capitate. Density of the spines on pericyst rather consistent. Penitabular spine arrangement
present typically around archeopyle and on operculum. In other areas of pericyst, penitabular arrangement sometimes absent or developed only partially. Paracingulum, being indicated by two ridges with row of spines, relatively wide and generally well delineated in cyst ambitus. Displacement of paracingulum not clear, probably not prominent. Parasulcus indicated by lackof paracingular rows of spines or ridges, and by shallow depression of the cyst in the ventral area, widening toward antapex. Endocyst rounded hexagonal with thin, smooth endophragm without ornament, appressed to periphragm except beneath horns. Paratabulation indicated incompletely by paracingulum, parasulcus, archeopyle and partial penitabular arrangement of spines on pericyst. Intercalary archeopyle always discernible, derived from loss of paraplate 2a, hexagonal, isodeltaform, Type I@, relatively large. Transverse archeopyle index= 0.49-0.77, average 0.59 (15 specimens measured). Accessory
archeopyle sutures along paraplate boundaries 3"/ 4" and 4"/ 5" sometimes present. Operculum always in place, adnate posteriorly.
Dimensions: Cyst overall length 42µm-63µm (average 51µm), width 33µm-57µm (average 41µm), 137 specimens measured. Spine length up to 2µm. Apical horn length 4.3µm; larger antapical horn length up to 5µm.
Occurrence: Abundant in the basal part of the lower part of the Sankebetsu Formation, Haboro area; Bellatudinium hokkaidoanum Zone, upper Middle (to Upper?) Eocene. Records in the Kamicharo and Kiroro Formations (Upper Oligocene to Lower Miocene), Shiranuka area, are interpreted to represent reworkingObserved range in this study: upper Middle (to Upper?) Eocene.
Remarks: This new species is characterized by its rounded pentagonal body shape, large, triangular apical pericoel and large, isodeltaform hexagonal, 2a archeopyle. The cornucavate wall relationships are distinctive in most of the observed specimens. Although the spines are not always entirely penitabular, the consistent presence of penitabular spines, at least in parts of the body, and the cornucavate wall relationships confirm the generic assignment of this species to Spinidinium. Variation of the cyst shape is not profound as indicated in Plate 1, figures 1-16. Height of epicyst more or less equal to that of hypocyst. Spinidinium pentagonum sp. nov. is distinguished from otherspecies of the genus by its angular, pentagonal ambital shape. It differs from Spinidinium? tripylum sp. nov. in overall cyst shape, apical pericoel shape and archeopyle configuration. It also differs from Spinidinium essoi Cookson and Eisenack 1967in having a larger apical pericoel. Spinidinium pentagonum sp. nov. frequently occurs with Trinovantedinium boreale, which also has a peridinioid outline, type I archeopyle and a general covering of relatively short spines. However, Spinidinium pentagonum sp. nov. is cornucavate and has a large, easily discernible archeopyle.This species is dominant in the basal part of the lower part of the Sankebetsu Formation, Haboro area, central Hokkaido. This horizon probably corresponds to the basal part of the Bellatudinium hokkaidoanum Zone.