A new species of Bolboforma (Incertae Sedis) from the Miocene of the Vøring Plateau, northern Norway

A new species, Bolboforma fragori sp. nov., is described and figured from D.S.D.P. Leg 38 Site 341, and its stratigraphic position downhole is documented.


INTRODUCTION
Bolboforma fragori is a new species belonging to the Incertae Sedis group Bolboforrna Daniels & Spiegler, 1974. There is speculation about the affinities of the group: for example, Rogl & Hochuli (1976) suggest that they may be planktonic algae (Chrysomondales) and Muller et al. (1985) believe that they may be algal reproductive bodies. Previously documented species have a limited stratigraphic occurrence. However, they also show a restricted geographic occurrence which may limit their use as zone fossils (Murray, in press). Despite this, they are distinctive in occurring in large numbers for short periods of time, and are common contributors to Oligocene, Miocene and Pliocene assemblages.

AREA OF STUDY
The specimens were obtained from D.S.D.P. Leg 38 Site 341 situated on the Voring Plateau (lat. 67'20.10"; long. 06"06.64'E). It was cored in 1439m of water. For location of Site 341 see Fig. 1.
Cores 26 and 27 have occasional bands of calcareous benthic foraminifera preserved; many are etched suggesting that the Miocene sediments were deposited near to the Calcium Carbonate Compensation Depth.
The occurrence of all Bolboforrna species recovered from Site 341 is summarised in Table 1.   Fig. 1 a- Description. Shell single chambered, compressed parallel to the equatorial plane, oral face with a short neck at the end of which is a circular aperture. The aboral surface is flattened. There are three lateral concentric flanges; the upper flange spirals down from the oral surface, whilst the lower flange spirals up from the aboral surface. These meet at the middle at a "central" flange which is discontinuous to accommodate the spirals. One end of this central flange bifurcates. The "central flange" is most prominent. The flanges are ornamented with invaginations and round ended processes. A circle of 3 to 8 round ended processes surrounds the apertural neck, and a similar row ornaments the aboral surface. The wall is glassy in appearance and calcitic. Dimensions. 165-215pm in diameter, including ornament.

Explanation of Plate 1
Remarks. Apertural neck length may vary, and the aperture may or may not possess a tooth plate. Ornament is commonly poorly preserved. No previously described species of Bolboforma bears flanges that are discontinuous spirals. All specimens viewed with a light microscope appear to bear three distinct continuous concentric flanges, however, under the S.E.M. only a few specimens exhibited this. The S.E.M. study revealed that the degree of spiralling of the flanges is variable. Some specimens show three distinct concentric flanges, but the central one is discontinuous and bifurcates at one end, whilst others do exhibit three truly concentric flanges. Differences in the degree of development of the flanges are considered to be variations within this species.
Comparison. There is a superficial resemblance to B. aculeata Daniels & Spiegler, 1974 in the nature of the processes; and to B. intermedia Daniels & Spiegler, 1974, which bears a flange which is a single continous spiral.

CONCLUSIONS
Bolboforma fragori sp. nov. is recorded from the Middle to Late Miocene sediments of D.S.D.P. Site 341 on the Voring Plateau. Samples of similar age from D.S.D.P. Sites 116, 352, and 336; and a selection of cores from the northern North Sea and West of Shetland shelf have been studied by the author. No specimens of B. fragori have been recovered from these cores. The stratigraphic and geographic range of B. fragori will hopefully be augmented by further studies.