Mizuhopecten ibaragiensis (Masuda, 1953)
MASUDA, K. 1953. A New Species of Patinopecten from Ibaragi Prefecture. Short Papers from the Institute of Geology and Paleontology, Tohoku University, 5: 41-50, pIs. 5, 6. [p. 44, pl. 5, figs. 1-5; pl. 6, figs. 1-5]
1953 Patinopecten ibaragiensis Masuda, 1953
1953 Patinopecten ibaragiensis Masuda, 1953
«Four left valves are referable to this species which was originally reported by Masuda (1953) from the upper Miocene Hatsu zaki Formation of Hitachi City, Ibaraki Prefecture. The left valve is usually ornamented with fine intercalary threads between the radial ribs and is easily distinguished from that of Patinopecten planicostulatus. But the right valves of these trvo species are very difficult to separate because of the broad range of variation of such characters as the radial ribs, auricles and byssal area. To clarify this problem, more study is needed with the right valves of these two species from the Futatsu-numa Sand.
This species was reported from the Kume Formation (Late Miocene - Early Pliocene) of Ibaraki Prefecture (Takahashi, 1986), and referred to some specimens which had been recorded under the name of "Pecten yessoensis" from the Miocene Ogawa Formation of Nagano Prefecture and from the Miocene Togeshita Formation of Hokkaido (Masuda, 1953).» O'HARA, S. & N. NEMOTO. 1988. Pectinids from the Taga Group of the Joban Coalfield. Saito Ho-on Kai Special Publication, Professor Tamio Kotaka Commemorative Volume: 481-496, pls. 1-4. [p. 491]
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Patinopecten (Mizuhopecten) ibaragiensis Masuda; S. O'Hara & N. Nemoto, 1988, Pectinids from the Taga Group of the Joban Coalfield, plate 1, figure 3.
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«Pecten yessoensis Jay, Yokoyama, 1931, p. 195, pI. 11, fig. 9 (non Jay, 1857) (?).
Patinopecten ibaragiensis Masuda, 1953b, p. 44, pI. 5, figs. 1-5, pI. 6, figs. 1-5; Kamada and Hayasaka, 1959, p. 21, pI. 2, figs. 8, 9. Holotype: – DGS, Reg. No. 103l.
Remarks: – This species is related to Patinopecten yessoensis (Jay), with which it has been mistaken, but is distinguishable therefrom by the smooth shell, folded byssal area, conspicuous byssal notch, conspicuous cardinal crura and by the existence of faint, fine radial sculpture on the auricles of the right valve. The characters of left valve also distinguish the present one from Jay's by its numerous intercalary threads between the radial ribs. Type locality, Geological formation and Age: – Cliff below the Sukegawa Gas Company, Miyata, Hitachi City, Ibaraki Prefecture (Lat. 36°37'18"N., Long. 1400 40'10"E.). Hitachi formation. Early Pliocene. Distribution: – Hitachi and Kume formations, Ibaraki Prefecture; Futaba-Tomioka formation, Fukushima Prefecture: all Early Pliocene in age. Occurrence: – Common in the calcareous coarse-grained sandstone of the Hitachi formation.» MASUDA, K. 1962. Tertiary Pectinidae of Japan. The Science Reports of the Tōhoku University [2nd. Series -Geology], 33 (2): 117-238, pls. 18-27. [p. 204]
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