Helicosphaeranudus walbersdorfensis

Helicosphaera walbersdorfensis Müller, 1974

Helicosphaera minuta Müller, 1981

Helicosphaera stalis Theodoridis, 1984

Helicolith has flush flange termination, and a central area with a relatively large central opening spanned by a conjunct oblique bar. Helicosphaeranudus walbersdorfensis is without a blanket.

Helicosphaeranudus walbersdorfensis primarily differs from Helicosphaeroides mullerae Varol (1989) Varol, n. comb. by lacking a blanket ( the wall confined the central opening and don’t impinge on the distal surface of the flange to form blanket) whilst the blanket partly covers the distal surface of the flange in Helicosphaera mullerae (Type I, Helicosphaeroides ampliaperta type).

Helicosphaeranudus walbersdorfensis is further distinguished from Helicosphaeroides mullerae by having a flange with a flush termination rather than expanded termination as in Helicosphaeroides mullerae.

Müller, C., 1974c. Nannoplankton aus dem Mittel-Miozän von Walbersdorf (Burgenland). Senckenbergiana Lethaea 55, 389-405.

Müller, C., 1981. Beschreibung neuer Helicosphaera-Arten aus dem Miozän und Revision biostratigraphischer Reichweiten einiger neogener Nannoplankton-Arten. Senckenbergiana Lethaea 61, 427-435.

Theodoridis, S., 1984. Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32, 1-271.

Varol, O., 1989a. Calcareous nannofossil study of the central and western Solomon Islands. Vedder, J.G., Bruns, T.R., (eds.), Geology and offshore resources of Pacific island arc-Solomon Island and Bougainville, Papua New Guinea Regions: Houston, Texas, Circum-Pacific Council for Energy and Mineral Resources Earth Sciences Series vol. 12, pp. 239-268.