Helicosphaera bownii

Helicosphaera bownii da Gama & Varol 2013

Helicolith having a Type III (Helicosphaera carteri type) blanket, an expanded flange termination a moderately large size central opening spanned by a conjunct traverse bar without a split.

Helicosphaera bownii differs from Helicosphaera mediterranea Müller (1981) by having a relatively small central opening and a bar without a split. The latter has a bar with a split which is parallel to the long axis of the helicolith.

Helicosphaera bownii is distinguished from Helicosphaera sellii (Bukry and Bramlette, 1969) Jafar and Martini (1975) in a similar way by having a relatively narrow central opening and its older stratigraphic occurrence. Moreover, the bar is often much narrower in Helicosphaera sellii than in Helicosphaera bownii

Bukry, D. & Bramlette, M. N., (1969b): Some new and stratigraphically useful calcareous nannofossils of the Cenozoic. - Tulane Studies in Geology. 7: 131-142.

Jafar, S. A. & Martini, E., (1975): On the validity of the calcareous nannoplankton genus Helicosphaera. - Senckenbergiana Lethaea. 56: 381-397.

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