Ceratolithales

Ceratolithaceae Norris, 1965

The order Ceratolithales includes a diverse group of coccoliths with distinct morphologies and optical properties, falling into two primary families:

Family Ceratolithaceae Norris, 1965 includes horseshoe-shaped coccoliths that may be associated with simple ring-shaped coccoliths in one of their life cycles, while the family Triquetrorhabdulaceae Lipps, 1969 includes rod-shaped coccoliths.

The following diagnostic features help identify and classify various genera within the order Ceratolithales based on optical properties and their morphologies under XPL.

Amaurolithus (syn. Nicklithus) and Pennalithus have a vertical optic axis relative to the microscope stage. Triquetrorhabdulus, Ceratolithus, Velonalithus, and Diplotsekouri
have radial optic axes parallel to the microscope stage.

Orthorhabdus has an inclined optic axis.

Ceratolithus, Orthorhabdus, and Velonalithus elongation characteristics are length-slow (+), while Triquetrorhabdulus and Diplotsekouri are length-fast (-).

Bramlette, M. N. & Wilcoxon, J. A. 1967. Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. Tulane Studies in Geology and Paleontology 5: 93-131.

Gartner, S. & Bukry, D. 1975. Morphology and phylogeny of the coccolithophycean family Ceratolithaceae. Journal of Research of the U.S. Geological Survey. 3: 451-465.

Kamptner, E., 1950. Über den submikroskopischen Aufbau der Coccolithen. Anzeiger der Österreichische Akademie der Wissenschaften, Mathematische-Naturwissenschafliche Klasse, Wien. 87, 152-158.

Lipps, J. H. 1969. Triquetrorhabdulus and similar calcareous nannoplankton. - Journal of Paleontology. 43(4): 1029-1032.

Martini, E. 1965. Mid-Tertiary calcareous nannoplankton from Pacific deep-sea cores. Colston Papers 17: 393-411.

Norris, R. E. 1965. Living cells of Ceratolithus cristatus (Coccolithophorineae). Archiv für Protistenkunde. 108: 19-21.

Raffi, I., Backman, J. & Rio, D. 1998. Evolutionary trends of tropical calcareous nannofossils in the late Neogene. Marine Micropaleontology. 35(1): 17-41.

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