Cretadmete, Blagovetshenskiy & Shumilkin, 2006

Nakrem, Hans Arne, 2017, Gastropods from the Late Jurassic - Early Cretaceous seep deposits in Spitsbergen, Svalbard, Zootaxa 4329 (4), pp. 351-374 : 363

Cretadmete sp.

( Fig. 8A–C )

2015 Maturifusidae ? gen. et sp. indet.; Hryniewicz et al. 2015a, table 1.

Description. Protoconch not preserved. Shell small, 4.5 mm in height and 5.3 mm in width, fusiform/turbiniform with two strongly convex whorls preserved. Suture moderately incised. Shell flank ornamented with numerous spiral cords arranged in two orders; each two 1 st order cords sandwich one weaker 2nd order cord. The spiral ornament is crossed by prosocline axial ridges with no clear knobs and the intersections, which, however, might be slightly undulating in the adapical portion of flank. Transition between flank and base without angulation, but distinct due to disappearance of axial ornamentation and 2nd order spiral cords. Aperture poorly preserved with no apertural elaborations visible. Anterior part of the aperture broken off. No umbilicus.

Material and occurrence: One specimen (PMO 224.762) from seep deposit #8, Sassenfjorden, Svalbard; Late Tithonian, Late Jurassic.

Remarks. This juvenile shell is remarkably similar to Cretadmete neglecta Blagovetshenskiy & Shumilkin, 2006 , from the Upper Hauterivian (Early Cretaceous) of the Ulyanovsk Region in Russia. Blagovetshenskiy & Shumilkin (2006) included six species in Cretadmete ranging in age from the Oxfordian to the Albian. We refrain from placing our shell into any of these species due to its fragmentary preservation. A similar type of teleoconch, but with entirely different cancellate protoconch, has been reported by Schröder (1995: pl. 7: 3–4) in a juvenile shell from the Albian of Germany, which has been interpreted by Bandel (1993) as a species of Rapana and considered by him to be the oldest record of the tonnoideans. Wollemann (1900, 1907, 1909) reported from the same strata several species similar to Cretadmete (but without protoconchs); this entire group of taxa requires thorough review.

Figures

FIGURE 8. A – C. Cretadmete sp., (PMO 224.762), Seep deposit # 8, Sassenfjorden, Svalbard; Late Tithonian (late Jurassic). D. Gastropoda gen. et sp. indet. (PMO 217.517), Seep deposit # 2, Sassenfjorden, Svalbard; late Berriasian (Early Cretaceous).