Obturolithus

Coccolithus stavensis Levin & Joerger, 1967

Elliptical to circular reiculofenestrid having unicycle distal and proximal shields and a tube cycle. The central area is covered by a plug distally and a central mesh proximally. The entire coccolith is birefringent under polarised light.

The plug may or may not cover the entire central area distally. Under the light microscope, the tube cycle and the plug cannot distinguish from each other.

Elliptical Groups

Obturolithus stavensis Group

Plug completely closed the central area

• Obturolithus burnsii Varol, in prep.; >14.0µm
• Obturolithus stavensis (Levin & Joerger, 1967) Varol, n. comb.; 10.0 - 14.0µm
• Obturolithus bisectus (Hay, Mohler & Wade, 1966) Varol, n. comb.; 8.0 - 10.0µm
• Obturolithus scissurus (Hay, Mohler and Wade, 1966) Varol, n. comb.; 6.0 - 8.0µm
• Obturolithus antarcticus (Haq, 1976) Varol, n. comb.; 4.0 - 6.0µm
• Obturolithus productellus (Bukry, 1975) Varol, n. comb.; <4.0µm

Obturolithus pseudolockeri Group

Plug partly closed the central area

• Obturolithus pseudolockeri (Jurasova, 1974) Varol, n. comb.; 10.0 - 14.0µm
• Obturolithus filewiczii (Wise & Wiegand in Wise, 1983) Varol, n. comb. ; 8.0 - 10.0µm

Circular Group

Obturolithus erbae Group

Plug completely closed the central area

• Obturolithus erbae (Fornaciari et al., 2010) Varol, n. comb.; 4.0 - 10.0µm

Obturolithus differs from Reticulofenestra Hay, Mohler & Wade (1966), Cribrocentrum Perch-Nielsen (1971) and Cyclicargolithus Bukry (1971) by having a distal plug. It is further differentiated from Reticulofenestra and Cyclicargolithus by having birefringent central mesh. The species of Obturolithus are primarily identified based on their shape and sizes. The ratio of pelaga to the central area and complete or incomplete plug are also used for speciations.

Bukry, D., (1971): Cenozoic calcareous nannofossils from the Pacific Ocean. - San Diego Society of Natural History Transactions. 16: 303-327.

Hay, W. W., Mohler, H. P. & Wade, M. E., (1966): Calcareous nannofossils from Nal'chik (northwest Caucasus). - Eclogae Geologicae Helvetiae. 59: 379-399.

Levin, H. L. & Joerger, A. P., (1967): Calcareous nannoplankton from the Tertiary of Alabama. - Micropaleontology. 13(2): 163-182.

Perch-Nielsen, K., (1971): Elektronenmikroskopische untersuchungen an Coccolithen und verwandten Formen aus dem Eozan von Danemark. - Biologiske Skrifter, Kongelige Danske Videnskabernes Selskab. 18(3): 1-76.