Amano et al.—New and Mesozoic-relict mollusks from Paleocene wood-fall communities
Table 6. Measurements of Neverita majimai Amano and Jenkins, n. sp. D=diameter, H=height; + =dimension in slightly imperfect case.
Locality Loc. 15
Loc. 15 Loc. 15 Loc. 16 Loc. 28 Loc. 15 Loc. 15 Loc. 10 Loc. 10 Loc. 28 Loc. 28 Loc. 28 Loc. 28 Loc. 32 Loc. 32 Loc. 38 Loc. 38
Specimen
JUE 16018, holotype JUE 16019-1, paratype JUE 16019-2, paratype JUE 16020, paratype JUE 16021, paratype JUE 16022-1 JUE 16022-2 JUE 16023-1 JUE 16023-2 JUE 16024-1 JUE 16024-2 JUE 16024-3 JUE 16024-4 JUE 16025-1 JUE 16025-2 JUE 16026-1 JUE 16026-2
D (mm) 7.7
4.9 3.4 6.0 4.0 6.4 4.9 5.1 4.3 5.7 4.1 4.6 3.3 4.1 3.9 9.0 7.6
H (mm) 7.3
5.3
3.7+ 5.7 5.1 6.6 3.5 4.2 4.7 6.1 4.2 4.0 3.6 2.8 2.9
11.5 6.7
transverse groove on the umbilical callus. Neverita globosa Gabb, 1869, from the upper Paleocene to upper Eocene in California, has a lower shell and a wider umbilical callus than the new species. Moreover, the transverse groove on the umbi- lical callus of the Californian species is sometimes recognized but very weak.
Subclass Heterobranchia Burmeister, 1837 Family Ringiculidae Philippi, 1853 Genus Biplica Popenoe, 1957
Type species.—Biplica heteroplicata Popenoe, 1957 (by origi- nal designation); early Senonian?
Biplica paleocenica Amano and Jenkins, new species urn:lsid:
zoobank.org:act:68D288A8-D9A4-4B8C-A01C- 16147F2F9126
Figure 4.8–4.16, Table 7
Type specimens.—Holotype, JUE 16027, from 900m upstream of the small river, 1.5km south to Ponkatsuhira-zawa, Urahoro Town, Hokkaido (Loc. 40; same as Amano and Olienik, 2014, loc. 1); paratypes, JUE 16028-1–2, from the type locality. Type locality: 900m upstream of the small river, 1.5km south to Ponkatsuhira-zawa, Urahoro Town, Hokkaido, Japan, 42°57'37''N, 143°37'41''E; Paleocene.
Diagnosis.—Small to moderate-sized ringiculid with smooth interior of outer lip. Spire rather high for genus; suture rather deep. No varix observed at outer lip. Surface sculptured with
18–26 (commonly 23–24) punctate spiral grooves, forming flat-topped spiral ribs between grooves. Inner lip covered with thin callus and two columellar folds.
Occurrence.—Upper Selandian to lowermost Thanetian, Katsuhira Formation, eastern Hokkaido, Japan.
Description.—Shell small to moderate-sized for genus (to 6.6mm H), elongate-ovate; spire rather high, occupying 0.10–0.32 of H. Suture rather deep, forming step between penultimate and last whorls. Shell of 3.5 whorls, including 1.5 whorls of smooth, low-spired protoconch. Surface sculptured by
643
Table 7. Measurements of Biplica paleocenica Amano and Jenkins, n. sp. D=diameter, H=shell height, NGB=number of grooves on body whorl, SH=spire height (mm), – =not available; + =dimension in slightly imperfect case.
Locality Specimen
Loc. 40 JUE 16027, holotype Loc. 40 JUE 16028-1, paratype Loc. 40 JUE 16028-2, paratype Loc. 41 JUE 16029-1 Loc. 41 JUE 16029-2 Loc. 41 JUE 16029-3 Loc. 41 JUE 16029-4 Loc. 41 JUE 16029-5 Loc. 39 JUE 16030 Loc. 7 JUE 16031 Loc. 1 JUE 16032-1 Loc. 1 JUE 16032-2 Loc. 3 JUE 16033 Loc. 30 JUE 16034 Loc. 32 JUE 16035-1 Loc. 32 JUE 16035-2 Loc. 32 JUE 16035-3 Loc. 32 JUE 16035-4 Loc. 32 JUE 16035-1
D (mm) H (mm) SH NGB 4.8
5.4 4.3 5.3 5.5 4.5 4.9 4.5 4.8 2.4 4.4 3.7 4.2 4.8 5.5 5.5 4.9 5.0 5.0
5.6 5.9 5.2 6.1 6.5 5.3 5.1 4.8 5.4 3.2 4.5 3.3 5.6 6.3 6.4 6.6
0.8 26 0.8 18 0.8 27 0.6 24 1.3 23 0.8 26 1.2 25 –
0.8
1.0 24 0.6 23 –
24
0.9 25 – –
0.9 1.6
1.1 24 –
5.8 –– 5.0+ –– 4.8 ––
2.1
18–26 spiral grooves (23–24 in most specimens) with small pits, separating flat-topped spiral ribs. Outer lip of most specimens thin, not dentate. Inner lip covered by thin callus, becoming thicker toward base, reaching posterior end of aperture. Two distinct columellar folds present near base.
Etymology.—Named after the age of this species, pointing out that it is the single relict species of this genus from the Paleocene.
Materials.—Six specimens from the type locality (Loc. 40); eight specimens from 50m upstream of the type locality (Loc. 41); four specimens from 25m downstream of the type locality (Loc. 39); one specimen from 50m upstream of Oppushinai-zawa (Loc. 7); two specimens from the river bank near Katsuhira (Loc. 1); one specimen from the outcrop below the Asahi Bridge near Katsuhira (Loc. 3); one specimen from 360m upstream of Katsuhira-zawa (Loc. 29); one specimen from410mupstream of Katsuhira-zawa (Loc. 30); six specimens from 575m upstream of Katsuhira-zawa (Loc. 32) ; see Table 7 for dimensions of well-preserved specimens among the material.
Remarks.—This new species can be distinguished from the Cretaceous species from Hokkaido, Biplica problematica (Nagao, 1932), which was originally described under the genus Avellana d’Orbigny, 1842. After Biplica was established by Popenoe (1957), Poyarkova and Dzhalilov (1985) allocated A. problematica to
Biplica.At the same time, they synonymized B. ovoides Blank, 1980 from the Maastrichtian deposits in the Koryak Upland with B. problematica. The type specimen of B. problematica has a very low spire and a very thick callus on the base, and is sculptured with 12 weak spiral grooves on the upper half of the last whorl. Biplica paleocenica n. sp. differs from B. osakaensis Kase, 1990 from the lower Maastrichtian Shindachi Formation in Osaka Prefecture, Honshu, by having an elongate shell and a step between the last and penultimate whorls, no varix at the outer lip, a higher spire (SH/H=0.14– 0.19 in B. osakaensis) although having a similar number of spiral grooves (24–27 in B. osakaensis). Biplica siberica Kaim
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