Nannotax Enabling nannofossil research

Description: horseshoe-shaped strongly birefringent ceratolith, with c-axis perpendicular to length. Arms variable in length and in degree of keel development.

Remarks: As noted in the generic description, ceratoliths show very consistent morphology in terms of asymmetry and pattern of development of ridges and teeth. Nonetheless, individual ceratoliths are highly variable in size and degree of ornamentation which has lead to discrimination of several “species”. In particular the forms telesmus and simplex appear to be simply more and less ornate forms of cristatus whilst rugosus appears to be an irregular variant as a result of poor preservation. The rostratus type of ceratolith is a highly ornate form common in modern assemblages.

NB The heterococcolith stage - Ceratolithus cristatus Kamptner, 1950 HET is described on a separate page.

Range: NN13 to 21.

Synonyms/Variants

• Ceratolithus rugosus Bukry and Bramlette, 1968 - ceratolith with thick arms and irregular form. These are almost certainly simply overgrown C. cristatus specimens. They are mostly recorded from the Pliocene but, as argued by Bergen (1984), this is probably a function of preservation being worse in older sediments.
• Ceratolithus simplex Bukry, 1979 - small, smooth form. This morphotype occurs throughout the range of C. cristatus and in modern assemblages.
• Ceratolithus separatus Bukry, 1979 - both arms slightly extended beyond the arch, a moderately ornamented form. This morphotype occurs in modern assemblages and is not obviously discrete from normal C. cristatus.
• Ceratolithus cristatus var. telesmus (Norris, 1965) Jordan and Young, 1990 [Cr. telesmus] - variety with long sinuous arms. Range: NN16 to 21, but possibly becomes more common in younger samples.
• Ceratolithus cristatus forma rostratus Borsetti & Cati 1976 [NB this form was not given a formal description and so is invalid]. Ceratolith with high keels and with the rodded keel of the right hand arm extended into an apical beak/rostrum.