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Melitasphaeridium aequabile
Melitasphaeridium aequabile Matsuoka, 1983
Taxonomic senior synonym: Melitasphaeridium choanophorum, according to Harland, Head and Wrenn in Head and Wrenn (1992, p.10).
Holotype: Matsuoka, 1983, pl.3, figs.7a-b
Locus typicus: Gomoto, Teradomari-cho, Niigata Prefecture, Central Japan.
Stratum typicum: below the Gomoto Tuff Beds in the Teradoma Formation - Late Miocene.
Age: Late Miocene
Original diagnosis: Matsuoka 1983, p. 114: Melitasphaeridium aequabile
Proximochorate cyst subspherical to ovoidal. Surface of the periphragm coarsely granular. Processes with recurved or aculeate distal extremities, intratabular, slender and hollow and distally opened. The precingular archeopyle formed by loss of the third paraplate. Operculum free. Paratabulation 3", 0-la, 6", 6c, 5-6"", 1 p (?), 1"" and 2-3 s.
Original description: Matsuoka 1983, p. 114, 115: Melitasphaeridium aequabile The proximochorate cyst is subspherical to ovoidal and consists of two layers, periphragm and endophragm adpressed between the processes. The outer surface of the periphragm is granular. The processes are intratanular, hollow and slender and do not exceed thirty in number. The distal extremities of these processes are originally aculate to recurved, but occasionally snapped off. The paracingulum is indicated by similar processes of other paraplates. The parasulcus has two or three processes similar to those of the paracingulum. The archeopyle is a distinctive precingular type formed by displacement of a single paraplate 3". The paratabulation is represented by the processes and the archeopyle, 3", 0-la, 6", 6c, 5-6"", lp(?), 1"" and 2-3s. The anterior and posterior intercalary processes are often reduced.
Dimensions: Holotype: length of cyst 36.2 Ám, width ot cyst 34.4 Ám, length of processes up to 14 Ám, width of processes 2.6 Ám. Other specimens: Length of cyst 26-38 Ám, width of cyst 26-36 Ám, length of processes 10-16 Ám, width of processes 1.7-2.6 Ám. Number of specimens measured: 20.
Occurrence: Rare to few in the Teradomari, Shiiya, Nishiyama and its equivalent formations, and Haizume Formations (Middle Miocene to Early Pleistocene).
Remarks: Matsuoka 1983, p. 114, 115
Judging from the archeopyle shape and intratabular processes not exceeding thirty in number, some specimens described as Hystrichosphaeridium pseudorecurvatum MORGENROTH 1966 by WILLIAMS & BRIDEAUX (1975, pl. 19, fig. 6), WILLIAMS & BUJAK (1977, pl. 1, fig. 5) and MANUM (1976, pl. 3, fig. 19) may be included in Melitasphaeridium aequabile sp. nov. The difference between this species and M. angustum will be mentioned in the description of the latter species. This species resembles M. choanophorum (DEFLANDRE & COOKSON) in having the distal ends flared and basically star-shaped, but differs from the latter in possessing a granular periphragm and shorter processes.
Taxonomic senior synonym: Melitasphaeridium choanophorum, according to Harland, Head and Wrenn in Head and Wrenn (1992, p.10).
Holotype: Matsuoka, 1983, pl.3, figs.7a-b
Locus typicus: Gomoto, Teradomari-cho, Niigata Prefecture, Central Japan.
Stratum typicum: below the Gomoto Tuff Beds in the Teradoma Formation - Late Miocene.
Age: Late Miocene
Original diagnosis: Matsuoka 1983, p. 114: Melitasphaeridium aequabile
Proximochorate cyst subspherical to ovoidal. Surface of the periphragm coarsely granular. Processes with recurved or aculeate distal extremities, intratabular, slender and hollow and distally opened. The precingular archeopyle formed by loss of the third paraplate. Operculum free. Paratabulation 3", 0-la, 6", 6c, 5-6"", 1 p (?), 1"" and 2-3 s.
Original description: Matsuoka 1983, p. 114, 115: Melitasphaeridium aequabile The proximochorate cyst is subspherical to ovoidal and consists of two layers, periphragm and endophragm adpressed between the processes. The outer surface of the periphragm is granular. The processes are intratanular, hollow and slender and do not exceed thirty in number. The distal extremities of these processes are originally aculate to recurved, but occasionally snapped off. The paracingulum is indicated by similar processes of other paraplates. The parasulcus has two or three processes similar to those of the paracingulum. The archeopyle is a distinctive precingular type formed by displacement of a single paraplate 3". The paratabulation is represented by the processes and the archeopyle, 3", 0-la, 6", 6c, 5-6"", lp(?), 1"" and 2-3s. The anterior and posterior intercalary processes are often reduced.
Dimensions: Holotype: length of cyst 36.2 Ám, width ot cyst 34.4 Ám, length of processes up to 14 Ám, width of processes 2.6 Ám. Other specimens: Length of cyst 26-38 Ám, width of cyst 26-36 Ám, length of processes 10-16 Ám, width of processes 1.7-2.6 Ám. Number of specimens measured: 20.
Occurrence: Rare to few in the Teradomari, Shiiya, Nishiyama and its equivalent formations, and Haizume Formations (Middle Miocene to Early Pleistocene).
Remarks: Matsuoka 1983, p. 114, 115
Judging from the archeopyle shape and intratabular processes not exceeding thirty in number, some specimens described as Hystrichosphaeridium pseudorecurvatum MORGENROTH 1966 by WILLIAMS & BRIDEAUX (1975, pl. 19, fig. 6), WILLIAMS & BUJAK (1977, pl. 1, fig. 5) and MANUM (1976, pl. 3, fig. 19) may be included in Melitasphaeridium aequabile sp. nov. The difference between this species and M. angustum will be mentioned in the description of the latter species. This species resembles M. choanophorum (DEFLANDRE & COOKSON) in having the distal ends flared and basically star-shaped, but differs from the latter in possessing a granular periphragm and shorter processes.