Hikidea osoensis, Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014

Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014, Mollusks from late Mesozoic seep deposits, chiefly in California, Zootaxa 3861 (5), pp. 401-440 : 408-409

Hikidea osoensis sp. nov.

( Fig. 3 E–I)

Diagnosis. Shell turbiniform, continuously convex and weakly inflated with weakly expressed concave ramp at the adapical suture. Surface smooth apart from some weak and hardly recognizable spirals and strongly prosocline growth lines.

Holotype: GZG.INV.84968, height H = 10.7 mm, width W = 9.6 mm.

Paratype: GZG.INV.84969, H = 8.8 mm, W = 7.0 mm.

Type locality and strata: Bear Creek, Colusa County, California, USA; locality # 4 in Kiel et al. (2008b). Great Valley Group, Grizzly Canyon member of Crack Canyon Formation; Valanginian (Early Cretaceous).

Other material: Five additional specimens from the type locality including a juvenile shell (GZG.INV.84970) illustrated in Fig. 3 I.

Description. Protoconch unknown. Shell turbiniform with four whorls, convex with no angulations. Concave ramp at the adapical suture weakly expressed. Juvenile shell ornamented by numerous spiral ribs. Adult shell surface smooth apart from some weak and hardly recognizable spirals and strongly prosocline growth lines. Generating curve circular, aperture tangential, peristome uninterrupted. Inner lip with narrow callus, outer lip not preserved. No umbilicus.

Remarks. Hikidea osoensis differs from H. omagariensis and H. yasukawensis by its much larger size and higher shell with more numerous whorls. The Recent Cantrainea nuda is also smaller and has a slightly angulated demarcation between the flank and the base, and less convex whorl flanks. This occurrence is the earliest known record of the genus.

Distribution. Type locality only.

Etymology. From Oso, Spanish for bear, referring to the name of type locality.

Figures

FIGURE 3. A. Limpet gastropod indet. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA; GZG. INV. 84967. B – D. Chilodonta? reticulata sp. nov. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA; holotype (GZG. INV. 84971). E – I. Hikidea osoensis sp. nov. from Valanginian (Early Cretaceous) seep carbonates at Bear Creek, Colusa County, California, USA. E – G. Holotype (GZG. INV. 84968). H. Paratype (GZG. INV. 84969). I. Juvenile (GZG. INV. 84970) displaying ornamentation of the early ontogenetic stage of the shell. J – O. Phanerolepida onoensis sp. nov. from Late Barremian (Early Cretaceous) seep site at Eagle Creek, Shasta County, California, USA; holotype (CAS 73130). J – K. Lateral views. L. Apical view. M. External prismatic shell layer. N. Internal nacreous shell layer. O. Detail of rhombohedric ornament pattern.