Diaphana

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 : 422

Diaphana sp.

( Fig. 9 E–F)

Description. Shell of small size (3.5 mm high and 3.2 mm wide), ovate-subglobose, apical opening narrow but deep, protoconch not preserved. Shell surface flat apart from prosocyrtic growth lines, slightly undulating sigmoidally in the adapical portion. Adapical margin of the outer lip slightly elevated, otherwise aperture not visible.

Material and occurrence: Single shell (GZG.INV.84994) from West Berryessa (probably Valanginian, Early Cretaceous).

Remarks. Diaphana sp. is similar to many cephalaspidean taxa belonging to different families or superfamilies (e.g. to aplysiomorphid Akera or bullid Bullopsis ) and we classify it as Diaphana based on its subglobose shell shape, poorly expressed ornamentation, sigmoidal growth lines, and the lack of a groove between the aperture and the preceding whorl typical for Akera ( Vokes 1939) . Cylichnids are usually densely ornamented and more elongated (see e.g. Sohl 1964). Diaphana is a cosmopolitan genus, species of which are cosmopolitan and occur in the modern oceans from the intertidal zone down to abyssal depths ( Ohnheiser & Malaquias 2014). Diaphanidae are considered to represent basal cephalaspideans ( Malaquias et al. 2009). A few other cephalaspidean taxa are known from other Cretaceous seep deposits, including Actaeoninia and Sulcoactaeon from the Early Cretaceous Koniakauer Schloss site in Czech Republic ( Ascher 1906; Kaim et al. 2013b), and Sulcoactaeon sp. from the Late Cretaceous Yasukawa seep site in Hokkaido, Japan (Kaim et al. 2009).

Figures

FIGURE 9. A – D. Pseudanchura biangulata (Anderson, 1938) from Late Barremian (Early Cretaceous) seep site at Eagle Creek, Shasta County, California, USA. A. CAS 73132. B – D. Juvenile CAS 73133. E – F. Diaphana sp. from? Valanginian (Early Cretaceous) seep carbonates at West Berryessa, Napa County, California, USA; GZG. INV. 84994.