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Melitasphaeridium angustum
From Fensome et al., 2019:
Melitasphaeridium angustum Matsuoka, 1983b, p.115–116, pl.3, figs.6a–b; pl.4, figs.1a–b,2a–b,4. Holotype: Matsuoka, 1983b, pl.4, figs.2a–b. Age: Pliocene–Early Pleistocene.
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Original description: [Matsuoka, 1983b]:
Melitasphaeridium angustum sp. nov.
PI. 3, fig. 6, pl. 4, figs. 1, 2, 4
Derivation of name: Latin, angustus, slender, with reference to the slender stalk of processes.
Diagnosis: Small subspherical cyst with intratabular, slender hollow and acuminate processes. Distal extremities closed. The precingular archeopyle formed by loss of 3" paraplate. Operculum free. Paratabulation 3', 6", 6c, 5-6'", 1"" and 2-3s.
Holotype: KMD slide NNS 17-4 (7.5/13 1.2), pl. 4, fig. 2. Sample NNS 17, Nishiyama Formation (Pliocene to Early Pleistocene).
Loc: Takitani-Shinden, Nishiyama-cho, Niigata Prefecture, Central Japan.
Description: The small proximochorate cyst is subspherical and consists of two layers, periphragm and endophragm adpressed between processes. The periphragm has a coarsely granular surface and forms intratabular hollow, slender, somewhat flexuous and acuminate processes with close distal tips. The parasulucus is not sufficiently clear. The archeopyle is a precingular type made by displacement of the 3" paraplate. The paratabulation shown by intratabular processes and the archeopyle is 3', 6", 6c, 5-6'", 1"" and 2-3s.
Dimensions: Holotype; Length of cyst 41.1 μm, width of cyst 36.2 μm, length of processes 11 μm, width of processes 2.1 μm. Other specimens; Length of cyst 33-42 μm, width of cyst 30-37 μm, length of processes 9.5-13 μm. Number of specimens measured: 5.
Occurrence: Rare in the Teradomari, Shiya and Nishiyama Formations (Middle Miocene to Pliocene or younger).
Remarks: The present species differs from Melitasphaeridium aequabile in having acuminate, slender
processes with closed distal extremities and also differs from M. choanophorum (DEFLANDRE & COOKSON) in possession of the coarsely granular periphragm.
Melitasphaeridium angustum Matsuoka, 1983b, p.115–116, pl.3, figs.6a–b; pl.4, figs.1a–b,2a–b,4. Holotype: Matsuoka, 1983b, pl.4, figs.2a–b. Age: Pliocene–Early Pleistocene.
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Original description: [Matsuoka, 1983b]:
Melitasphaeridium angustum sp. nov.
PI. 3, fig. 6, pl. 4, figs. 1, 2, 4
Derivation of name: Latin, angustus, slender, with reference to the slender stalk of processes.
Diagnosis: Small subspherical cyst with intratabular, slender hollow and acuminate processes. Distal extremities closed. The precingular archeopyle formed by loss of 3" paraplate. Operculum free. Paratabulation 3', 6", 6c, 5-6'", 1"" and 2-3s.
Holotype: KMD slide NNS 17-4 (7.5/13 1.2), pl. 4, fig. 2. Sample NNS 17, Nishiyama Formation (Pliocene to Early Pleistocene).
Loc: Takitani-Shinden, Nishiyama-cho, Niigata Prefecture, Central Japan.
Description: The small proximochorate cyst is subspherical and consists of two layers, periphragm and endophragm adpressed between processes. The periphragm has a coarsely granular surface and forms intratabular hollow, slender, somewhat flexuous and acuminate processes with close distal tips. The parasulucus is not sufficiently clear. The archeopyle is a precingular type made by displacement of the 3" paraplate. The paratabulation shown by intratabular processes and the archeopyle is 3', 6", 6c, 5-6'", 1"" and 2-3s.
Dimensions: Holotype; Length of cyst 41.1 μm, width of cyst 36.2 μm, length of processes 11 μm, width of processes 2.1 μm. Other specimens; Length of cyst 33-42 μm, width of cyst 30-37 μm, length of processes 9.5-13 μm. Number of specimens measured: 5.
Occurrence: Rare in the Teradomari, Shiya and Nishiyama Formations (Middle Miocene to Pliocene or younger).
Remarks: The present species differs from Melitasphaeridium aequabile in having acuminate, slender
processes with closed distal extremities and also differs from M. choanophorum (DEFLANDRE & COOKSON) in possession of the coarsely granular periphragm.