Nannotax Enabling nannofossil research

Description: Coccosphere monothecate, ellipsoidal with apical opening. Coccoliths arranged on coccosphere with long axis aligned equatorially and broader flange directed toward apical opening.

Coccoliths placolith-like, with asymmetrical distal flange, one side broader with a variable extension, other side narrow and in many species with 8-10 teeth projecting into central area. Plate in central area formed by extension of tube elements inward, usually with irregular central fissure. No discrete circumflagellar coccoliths.

Life cycle: Combination cells of Polycrater sp. and Alisphaera gaudii have been observed (Cros et al. 2000a, Cros & Fortuño 2002).

Type species: A. ordinata.

Remarks: The species-level taxonomy of the genus was reviewed by Jordan & Chamberlain (1993) and by Kleijne et al. (2002). NB As well as describing new species Kleijne et al (2002) significantly revised the taxonomic concepts of A. unicornis and A. spatula. Essentially A. unicornis sensu Jordan & Chamberlain (1993) corresponds to A. gaudii whilst A. spatula sensu Jordan & Chamberlain (1993) corresponds to A. unicornis sensu Kleijne et al. (2002). The confusion stems from the fact that Okada & McIntyre (1977) illustrated two rather different specimens as A. unicornis, See Kleijne et al. (2002) for detailed synonymies.

Fossil record: Only occasional specimens observed and these are best refered to as Alisphaera sp.

Mid Pliocene fossil Alisphaera coccolith (image from Daniela Crudeli)