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Impagidinium japonicum
From Fensome et al., 2019:
Impagidinium japonicum Matsuoka, 1983b, p.120–121, pl.6, figs.2a–c,3a–b,4–5; text-figs.13A–B. Holotype: Matsuoka, 1983b, pl.6, figs.2a–c; Jan du Chêne et al., 1986a, pl.59, figs.1–3; Zorzi et al., 2019, pl.4, figs.1–6. Taxonomic junior synonym: Impagidinium pacificum, according to Bujak and Matsuoka (1986, p.236). Age: Pliocene or younger.
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Original description: [Matsuoka, 1983b]:
Impagidinium japonicum sp. nov.
Pl. 6, figs. 3-5, Text-Fig. 13
Derivation of name: Reference to occurrence location.
Diagnosis: Chorate cyst spherical to ellipsoidal. Surface of autophragm faintly granular. Parasutural septa well developed and one third to one fifth of cyst diameter. Paratabulation 4', 6", 6c, 5-6'", 1p, 1"" and 5s. Archeopyle precingular and formed by displacement of the 3" paraplate.
Holotype: KMD slide NNS 23-2 (19.0/135.7), pl. 6, fig. 2. Sample NNS 23, Nishiyama Formation - Pliocene or younger. Loc.: Ochimizu, Wajima-mura, Nigata Prefecture, entral Japan.
Description: The chorate cyst composed only of an autophragm is spherical to ellipsoidal. The outline with parasutural septa shows a polygonal shape in dorso-ventral view. The surface of the autophragm and parasutural septa is finely granular. The boundary between the apical paraplate 1' and 4' is obscure in detail, but is suggested by a reduced minute parasutural septum. The precingular paraplate 6° is triangular in shape. The paracingulum is laevorotary and displaced at two to three times of its own width. The parasutural septa are well developed and are
one third to one ffth of the cyst diameter. The archeopyle is a typical precingular type formed by loss of the 3" paraplate. The paratabulation is represented as 4', 6", 6c, 5-6'", 1p, 1"' and 5s. If the paraplate 1'" is too small not to be observed, the postcingulum may consist originally of six paraplates.
Dimensions: Holotype: Length of cyst 47 μm, width of cyst 47 μm, height of parasutural septa up to 12 μm. Other specimens: i.ength of cyst 38-55 μm, width of cyst 34-53 μm, height of parasutural septa 7.0-13.7 μm. Number of specimnens measured: 25.
Occurrence: Rare to few in the Nishiyama Formation and its equivalent formations, and Haizume Formation (Pliocene to Eariy Pleistocene).
Remarks: The present species is similar to Impagidinium strialatum (WALL) in having relatively high parasutural septa. The latter species differs from the former in possessing elongate and smaller cyst body. I. japonicum is also different from I. patulum (WALL) and I. multiplexum (WALL & DALE) in having characteristic parasutural septa. The specimens obtained from the Haizume Formation are smaller than those of the lower part
of the Nishiyama Formation.
Impagidinium japonicum Matsuoka, 1983b, p.120–121, pl.6, figs.2a–c,3a–b,4–5; text-figs.13A–B. Holotype: Matsuoka, 1983b, pl.6, figs.2a–c; Jan du Chêne et al., 1986a, pl.59, figs.1–3; Zorzi et al., 2019, pl.4, figs.1–6. Taxonomic junior synonym: Impagidinium pacificum, according to Bujak and Matsuoka (1986, p.236). Age: Pliocene or younger.
---------------------------------------------------------------------------------------------------
Original description: [Matsuoka, 1983b]:
Impagidinium japonicum sp. nov.
Pl. 6, figs. 3-5, Text-Fig. 13
Derivation of name: Reference to occurrence location.
Diagnosis: Chorate cyst spherical to ellipsoidal. Surface of autophragm faintly granular. Parasutural septa well developed and one third to one fifth of cyst diameter. Paratabulation 4', 6", 6c, 5-6'", 1p, 1"" and 5s. Archeopyle precingular and formed by displacement of the 3" paraplate.
Holotype: KMD slide NNS 23-2 (19.0/135.7), pl. 6, fig. 2. Sample NNS 23, Nishiyama Formation - Pliocene or younger. Loc.: Ochimizu, Wajima-mura, Nigata Prefecture, entral Japan.
Description: The chorate cyst composed only of an autophragm is spherical to ellipsoidal. The outline with parasutural septa shows a polygonal shape in dorso-ventral view. The surface of the autophragm and parasutural septa is finely granular. The boundary between the apical paraplate 1' and 4' is obscure in detail, but is suggested by a reduced minute parasutural septum. The precingular paraplate 6° is triangular in shape. The paracingulum is laevorotary and displaced at two to three times of its own width. The parasutural septa are well developed and are
one third to one ffth of the cyst diameter. The archeopyle is a typical precingular type formed by loss of the 3" paraplate. The paratabulation is represented as 4', 6", 6c, 5-6'", 1p, 1"' and 5s. If the paraplate 1'" is too small not to be observed, the postcingulum may consist originally of six paraplates.
Dimensions: Holotype: Length of cyst 47 μm, width of cyst 47 μm, height of parasutural septa up to 12 μm. Other specimens: i.ength of cyst 38-55 μm, width of cyst 34-53 μm, height of parasutural septa 7.0-13.7 μm. Number of specimnens measured: 25.
Occurrence: Rare to few in the Nishiyama Formation and its equivalent formations, and Haizume Formation (Pliocene to Eariy Pleistocene).
Remarks: The present species is similar to Impagidinium strialatum (WALL) in having relatively high parasutural septa. The latter species differs from the former in possessing elongate and smaller cyst body. I. japonicum is also different from I. patulum (WALL) and I. multiplexum (WALL & DALE) in having characteristic parasutural septa. The specimens obtained from the Haizume Formation are smaller than those of the lower part
of the Nishiyama Formation.