Cribrocentrum

Coccolithus foveolatus Reinhardt, 1966a

Elliptical Groups

Cribrocentrum ornatum Group

with a single cycle of large pores & non-porous central field

• Cribrocentrum ornatum (Müller, 1970b) Varol, 2025a.; 5.0 - 10.0µm
• Cribrocentrum pectinatum (Roth, 1970) Varol, n. comb.; <5.0µm

Cribrocentrum retiformis Group

with a single cycle of large pores & perforated central field

• Cribrocentrum retiformis (Reinhardt, 1966a) Varol, 2025a; 5.0 - 10.0µm
• Cribrocentrum foveolatum (Reinhardt, 1966a) Perch-Nielsen, 1971c; <5.0µm

Cribrocentrum gartneri Group

with numerous random perforations

• Cribrocentrum gartneri (Roth & Hay in Hay et al. 1967) Varol n. comb.; 5.0 - 10.0µm

Cribrocentrum oamaruensis Group

without numerous random perforations

• Cribrocentrum oamaruensis (Deflandre in Deflandre & Fert 1954) Varol, n. comb.; >13.0µm
• Cribrocentrum lockeri (Muller, 1970b) Varol, n. comb. ; 10.0 - 13.0µm
• Cribrocentrum antillarum (Black,1967) Varol, n. comb.; 5.0 - 10.0µm
• Cribrocentrum macmillanii (Dunkley Jones, Bown & Pearson, 2009) Varol, n. comb.; <5.0µm

Circular Group

Cribrocentrum reticulatum Group

• Cribrocentrum isabellae Catanzariti et al. in Fornaciari et al., 2010; >12.0µm
• Cribrocentrum reticulatum (Gartner & Smith, 1967) Perch-Nielsen, 1971c; 5.0 - 12.0µm
• Cribrocentrum artuziae (Varol, 1989b) Varol, n. comb. ; <5.0µm
• Cribrocentrum oculus-electrae (Deflandre & Fert, 1954) Varol, n. comb. ; <5.0µm

The circular to elliptical placoliths comprise single-tiered distal and proximal shields, a single tube cycle, and a central area with a permanent cover often pierced by pores, all
exhibiting inclined extinction and length-fast (-) elongation. The extinction angle measured on the distal side is typically about 83° on the distal shield and 60° on the tube cycle.

Cribrocentrum differs from Noelaerhabdus by lacking a distal process and from Reticulofenestra and Cyclicargolithus by having a permanent central cover. Dictyococcites differs from the above genera by having a tube cycle that often completely, rarely partially blocks the central area. An overview of Cribrocentrum species is provided in Table 3 in Varol (2025a).

Deflandre, G. & Fert, C. 1954. Observations on current and fossil coccolithophorids in ordinary and electron microscopy. Annales de Paléontologie 40: 115-176.

Dunkley Jones, T., Bown, P. R. & Pearson, P. 2009. Exceptionally well preserved upper Eocene to lower Oligocene calcareous nannofossils (Prymnesiophycidae) from the Pande Formation (Kilwa Group), Tanzania. Journal of Systematic Palaeontology 7(4): 359-411.

Fornaciari, E., Agnini, C., Catanzariti, R., Rio, D., Bolla, E. M. & Valvasoni, E. 2010. Mid- Latitude calcareous nannofossil biostratigraphy and biochronology across the middle to late Eocene transition. Stratigraphy 7(4): 229-264.

Gartner, S. & Smith, L. A. 1967. Coccoliths and related calcareous nannofossils from the Yazoo Formation (Jackson, Late Eocene) of Louisiana. University of Kansas Paleontological Contributions, Papers 20: 1-7.

Hay, W. W., Mohler, H. P., Roth, P. H., Schmidt, R. R. & Boudreaux, J. E. 1967. Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation. - Transactions of the Gulf-Coast Association of Geological Societies 17: 428-480.

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

Müller, C. 1970b. Nannoplankton-Zonen der Unteren-Meeresmolasse Bayerns. Geologica Bavarica 63: 107-118.

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

Reinhardt, P. 1966a. Fossile Vertreter coronoider und styloider Coccolithen (Family Coccolithaceae Poche 1913). Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 8: 513-524.

Roth, P. H. 1970. Oligocene calcareous nannoplankton biostratigraphy. Eclogae Geologicae Helvetiae 63: 799-881.

Black, M. 1967. New names for some coccolith taxa. - Proceedings of the Geological Society of London 1640: 139-145.

Varol, O. 1989b. Eocene calcareous nannofossils from Sile (northwest Turkey). Revista Española de Micropaleontología 21: 273-320.

Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222