Watznaueria bayackii

Watznaueria bayackii Worsley, 1971

Small- to medium-sized (3.0–7.0 µm), elliptical species of Watznaueria, characterised by a distal shield that is larger than the proximal shield and a narrow central area bearing two small depressions positioned at opposite ends along the long axis, connected by a suture. The central area and its features are resolvable only under phase-contrast illumination.

 In plan view under cross-polarised light, the shields display white interference colours that decrease in intensity towards the periphery, where only the distal shield is present, and show inclined extinction lines and length-fast (–) elongation. The central area is not resolvable under cross-polarised light. Extinction angles show considerable variation, typically ranging from about 65° to 75°.

Watznaueria bayackii differs from Watznaueria diaphanae (= Watznaueria supracretacea, invalid according to ICN Art. 35.1) in its optical properties: Watznaueria bayackii exhibits inclined extinction with extinction angles of about 65–75°, whereas Watznaueria diaphanae displays parallel extinction (0°).

Watznaueria bayackii is further distinguished from Watznaueria sp.1 by the nature of the central area. In Watznaueria bayackii, the central area is not resolvable under cross-polarised light, whereas in Watznaueria sp.1, the narrow, elongate central area is visible and exhibits dimmer interference colours than the shields.

Reinhardt, P. 1965. Neue Familien für fossile Kalkflagellaten (Coccolithophoriden, Coccolithineen). Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 7: 30-40.

Worsley, T. R., 1971. Calcareous nannofossil zonation of Upper Jurassic and Lower Cretaceous sediments from the Western Atlantic. In: Farinacci, A. (ed.), Proceedings of the Second Planktonic Conference Roma 1970. Edizioni Tecnoscienza, Rome vol. 2, pp. 1301-1321.