Nippononectes monobensis Tashiro, 1982
TASHIRO, M. 1982. A new pectinid genus Nippononectes from the Cretaceous of Japan. Memoirs of the Faculty of Science, Kochi University [Series E - Geology], 3: 1-6, pIs. 1, 2. [p.3, pl. 2, figs. 6-9]
1982 Nippononectes monobensis Tashiro, 1982
M. Tashiro, 1982, plate 2.
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«Material:— Holotype, KSG 2996, external mould of left valve, from Mizutani of Kajisako, Monobe Area, Kochi Prefecture; a paratype, KSG 2997, external mould of left valve, from a little lower horizon than the locality of holotype, Mizutani; another paratype, KSG 2998, left internal mould, from the same locality of KSG 2997.
Description:— Shell very small, roundly ovate, a little taller than length, weakly inflated; umbo less prominent, located at nearly mid-point of the valve length; apical angle about 80°; anterior and posterior margins nearly straight with about a half length of the valve in each; ventral margin well arched; hinge line nearly straight, horizontal with about a half length of the valve; anterior ear larger than posterior one, subvertically truncated on the anterior side; posterior ear small, obliquely truncated; disk ornamented with two sorts of the ribs; one of them divaricated striae, very fine but distinct; the other ribs radiated, narrower than their interspaces, consisted with numerous primary and less numerous secondary elements with about 30 in total numbers in the left valve; inner surface smooth; inner ventral margin smooth.
Remarks:— The radial ribs are narrower than their interspaces with about a half breadth to the latter, strongly spinose on the both lateral ventral parts on the surface of the left valve. The external and internal features of right valve are unknown. The secondary radial ribs appear irregularly in the later stage of the valve, near the ventral margin, very narrow to the primary ribs.
Comparison:— This species resembles Nippononectes tamurai s. s (Tashiro) (op. cit.), in the weak and delicate radial ribs on the surface, but differs in having its less numerous radial ribs and smaller size than those of N. tamurai s. s.
Occurrence:—Fine grained and dark greenish sandstone of the lower part of the Kajisako Formation at Mizutani of Kajisako, Odochi of Monobe, Kochi Prefecture, occurring together with Inoceramus teshioensis (Upper Turonian). Dark greenish sandstone of the lower part of the Kajisako Formation at a little lower horizon than the above locality, occurring together with Inoceramus hobetsensis and Inoceramus teraokai (Middle Turonian).»
MASAYUKI TASHIRO, 1982
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