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Thu, 11/10/2007 - 14:20 — Jeremy Young
Calcidiscus tropicus Kamptner, 1956 sensu Gartner, 1992
Description: Species of Calcidiscus producing circular coccoliths with open central-area, 7-10μm.
Remarks: Not always separated from C. leptoporus. Miocene forms often have a bicyclic proximal shield, in Pliocene forms a coarse grill is often visible in central opening. Larger forms (>10µm) are separated as C. macintyrei, possibly evolves into C. quadriperforatus.
Range: NN4 to 19.
Original description:
Variants;
- C. leptoporus ssp centrovalis (Stradner and Fuchs, 1980) Perch-Nielsen, 1984 - similar to C. tropicus but sub-circular;
- C. carlae (Lehotayova and Priewalder, 1978) Janin, 1992 [Cycloperfolithus] - Paratethyan form, with fine grill in central-area, and bicyclic proximal shield.
Comment and discussion:
- 1261 reads
nanno-taxonomy: Calcidiscus; Calcidiscus tropicus
Comments
C.carlae as a marker in the Pliocene
In the Gulf of Mexico the LAD of C. carlae (the type with a fine grill in the central area) is used as a marker equivalent in age to the LAD of Discoaster tamalis or slightly younger, depends on who you talk to. If you talk to me, they are equivalent. I found the same co-occurence of these two taxa in the South Pacific in the material from ODP leg 135.
The grill is often difficult to discern without the use of phase contrast.
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