Two new bairdiid ostracod species from the early Barremian–Hauterivian of the northern and central North Sea to the Atlantic margin off Norway

Michael Ayress,Tom Gould

doi:10.5194/jm-37-195-2018

Abstract

Abstract. Two new species of bairdiid Ostracoda are described from the lower Barremian – Hauterivian interval of the Valhall and Åsgard formations in the northern and central North Sea and Atlantic margin off Norway. The new species are Pontocyprella valhalla (lsid:zoobank.org:act:CA6B273F-CFF6-4C38-B9F4-18188225A711, 18 January 2018) and Bairdia asgarda (lsid:zoobank.org:act:4A4DC817-A028-45FB-9287-ABF3794F2FCB, 18 January 2018). These species dominate the ostracod assemblage that occurs abundantly in early Barremian–Hauterivian deep marine sediments of the northern and central North Sea and Haltenbanken area off Norway. Pontocyprella valhalla is restricted to this interval and because of its large size and distinct shape is a useful stratigraphic marker species, its last appearance being within the early Barremian.

Highlights

We describe two species of bairdiids that dominate the early Barremian–Hauterivian ostracod assemblage, and we show that they can be recognised by virtue of their distinctive shape and large size
We found no relationship between size and stratigraphic level within the early Barremian to Hauterivian range
At present insufficient specimens in the material studied here preclude full comparisons, but the largest specimen we found is an instar whose outline has a steep posterior slope (Fig. 1q, r) similar to that of P. harrisiana

Summary

Material and methods

Observations documented are based on a large number of proprietary data examined over the last 30 years during routine biostratigraphical analyses of wells drilled in the North Sea and Atlantic margin off Norway. The type specimens selected for this report are from 35/12-5S, collected from a ditch cutting sample at 2794 m (depth below KB). Statements regarding the stratigraphical and geographical distribution of the species are based on observations pertaining to proprietary data from some 200 well sections drilled in the North Sea and North Atlantic continental shelf. All specimens are from the ditch cutting sample at 2794 m, well 35/12-5S. 19866, carapace, right view, adult female; (2) paratype OS Cat no. 19869, carapace, dorsal view, adult male; (4) paratype OS Cat no. 19868, carapace, right view, adult male; (5) paratype OS Cat no. Nos. (3–5): Pontocyprella valhalla n. sp.: (3) paratype OS Cat no. 19869, carapace, dorsal view, adult male; (4) paratype OS Cat no. 19868, carapace, right view, adult male; (5) paratype OS Cat no. 19879, carapace, right view, A-1? female

Systematic palaeontology

Findings

Discussion

Conclusions