Hokkaidoconcha occidentalis ( Stanton, 1895 )
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publication ID |
https://doi.org/ 10.4202/app.2008.0412 |
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persistent identifier |
https://treatment.plazi.org/id/03DC9B54-FFE1-337E-FCD0-43727D90CB6A |
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treatment provided by |
Felipe |
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scientific name |
Hokkaidoconcha occidentalis ( Stanton, 1895 ) |
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Hokkaidoconcha occidentalis ( Stanton, 1895)
Fig. 5A–C View Fig .
1895 Hypsipleura? occidentalis sp. nov.; Stanton: 70, pl. 13: 3, 4.
Material.— Stanton’s specimens ( USNM 23077 About USNM ), two specimens from NW Berryessa (site 10; figured specimen: UCMP
555091), three specimens from Paskenta (site 2), and two specimens from Wilbur Springs (site 5). Stanton (1895) did not designate a holotype. His material consists of a gutta−pertcha cast with many specimens, one of which is indicated by an arrow scratched into the cast, and fits his illustration of Hypsipleura? occidentalis . This specimen is here designated as lectotype of Hypsipleura? occidentalis and figured on Fig. 5A View Fig .
Description.—Small, slender cerithiform shell with at least five slightly convex whorls and fine, incised suture. Ribs varix−like and opisthocyrt to various degrees; additional sculpture of 6–8 fine spiral threads that are pronounced between axial ribs but almost invisible on ribs; these threads are equally spaced except for the uppermost, subsutural spiral, which is a bit set apart from those below, this subsutural spiral often forms tubercles at the intersection with the axial ribs. Basal margin convex, marked by fading of axial ribs, and onset of strong spiral cords; aperture oval−lenticular. The lectotype is 9 mm high and 3 mm wide.
Discussion.—From Eocene to Miocene cold seep carbonates in Barbados, Gill et al. (2005) described a quite similar species as “zygopleurid sp. A”. In contrast to Hokkaidoconcha occidentalis , that species has a sharply delimited basal edge, a feature that is common in modern epitoniids but occurs only occasionally in Mesozoic zygopleurids.
Stratigraphic and geographic range.—Tithonian (Upper Jurassic) to Hauterivian (Lower Cretaceous), seep carbonates in the Great Valley Group at Paskenta, NW Berryessa, and Wilbur Springs.
| UCMP |
University of California Museum of Paleontology |
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