Hokkaidoconcha morenoensis, Kiel & Campbell & Elder & Little, 2008

Kiel, Steffen, Campbell, Kathleen A., Elder, William P. & Little, Crispin T. S., 2008, Jurassic and Cretaceous gastropods from hydrocarbon seeps in forearc basin and accretionary prism settings, California, Acta Palaeontologica Polonica 53 (4), pp. 679-703 : 686

Hokkaidoconcha morenoensis sp. nov.

Fig. 5F, G .

Etymology: After the type locality at Moreno Gulch, California, USA.

Type material: Holotype: LACMIP 13483 . Specimen with five whorls showing axial ribs across the entire height of the whorls and spiral sculpture on the base; paratype: LACMIP 13484 , from the type locality.

Type locality: Moreno Gulch , California, USA .

Type horizon: Santonian (Upper Cretaceous) seep carbonates at Moreno Gulch, Great Valley Group.

Material.— Type specimens and several specimens from the type locality and from Romero Creek (site 13) .

Diagnosis.—Slender turriculate shell with slightly convex whorls; ribs widely spaces, variably opisthocyrt to opisthocline, on entire whorl or restricted to upper part; base with fine spiral cords.

Description.—Teleoconch with eight or more whorls, suture incised; whorls sculptured by eight to ten varix−like ribs per whorl, interspaces between ribs two to four times the width of the ribs; ribs variably developed on the entire height of the whorl to completely obsolete; aperture unknown. Holotype with five whorls 8 mm high and 3 mm wide, tallest specimen with eight whorls 16 mm high and 4 mm wide.

Discussion.— Hokkaidoconcha morenoensis is most similar to H. tehamaensis but differs in having whorls that are more convex and in lacking the spiral sculpture present on whorl flanks of H. tehamaensis , H. occidentalis , and H. bilirata .

Stratigraphic and geographic range.—Santonian–Campanian (Upper Cretaceous) seep carbonates, Great Valley Group, California, USA.

Figures

Fig. 5. Late Jurassic and Early Cretaceous abyssochrysoids Hokkaidoconcha spp. and Abyssochrysos? giganteum sp. nov. from seep carbonates in California, USA. A–C. Hokkaidoconcha occidentalis (Stanton, 1895). A. Lectotype (USNM 23077) from Paskenta (Tithonian; site 2). B. Specimen (CAS 70391) with well−developed spiral sculpture from Wilbur Springs (Hauterivian; site 5). C. Specimen (UCMP 555091) with poorly developed spiral sculpture from NW Berryessa (Tithonian; site 10). D, E. Hokkaidoconcha tehamaensis sp. nov. from Paskenta (Tithonian; site 10). D. Holotype (UCMP 555092); apertural (D1) and lateral (D2) views. E. Paratype (CAS 70390), note fading axial ribs on flank.F, G. Hokkaidoconcha morenoensis sp. nov. from Moreno Gulch (Santonian; site 14) F. Holotype (LACMIP 13483) with well−developed axial ribs and spiral sculpture on base. G. Paratype (LACMIP 13484) with fading axial ribs on later whorls. H. Hokkaidoconcha bilirata sp. nov., holotype (UCMP 555093) from Wilbur Springs (Hauterivian; site 5). I. Hokkaidoconcha sp. (UCMP 555094) from NW Berryessa (Tithonian; site 10). J, K. Abyssochrysos? giganteum sp. nov. from E Berryessa (Lower Cretaceous; site 12). J. Holotype (UCMP 555095). K. Paratype (UCMP 555096).