Nippononectes kozaii 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. 5, pl. 2, figs. 10, 11]
1982 Nippononectes kozaii Tashiro, 1982
M. Tashiro, 1982, plate 2.
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«Material:— Holotype, KSG 2992, external mould of left valve, from the southern bank of the Monobe River near Nagase Dam-site, Monobe Area, Kochi Prefecture; a paratype, KSG 2993, external mould of left valve, from a little lower horizon than the locality of the holotype; another paratype, KSG 2994, external mould of right valve, from the same locality of KSG 2993.
Description:— Shell roundly ovate, slightly taller than high, weakly inflated; umbo not prominent; apical angle about 70°; anterior and posterior margins nearly straight; ventral margin semicircular; hinge line straight, horizontal with about a half length of the valve; both lateral margins of ears subvertically truncated; byssal notch very deep with 6 or so ctenolia; disk ornamented with two sorts of ribs; one of them radiated, strong but a little narrower than their interspaces, number about 30 in primary and several in secondary, generally spinose on both lateral parts of the ventral area; secondary ribs narrower than the primary ones, appear irregularly on the ventral part; the other sorts of the ribs composed of divaricated striae, very fine but distinct, appear on each interspace of the radial ribs; growth lines well developed on the later stage of the valve, finely laminated; ears ornamented in the same way as the disk; cardinal crurae strong, below the hinge line.
Observation:— This species is characterized by the strong radial ribs and distinctly laminated growth lines on the surface. The ears are characterized by reticulated sculpture which is composed of the radial ribs and strong growth lines, broader in the anterior side than in posterior side.
Comparison:— This species is similar to Nippononectes eleganus (op. cit.), in its taller valve and larger ears than those of the other species of Nippononectes. This species is, however, discriminated from N. eleganus in its larger valve, larger apical angle and more numerous secondary ribs than those of N. eleganus.
Occurrence:—Holotype is collected from the silty sandstone of the Fukigoshi Formation at the western roadside exposure near the Nagase Dam-site, Nagase, Kahoku-cho, Monobe Area, Kochi Prefecture, by Mr. Kozai. Paratypes are from the silty sandstone of the same formation at about 40m lower horizon than the locality of the holotype. The geological
age is probably determinable to the lower Cenomanian.» MASAYUKI TASHIRO, 1982
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