A new, very small to small (2.4 to 4.6μm) reticulofenestrid coccolith, Reticulofenestra calicis n. sp., is described by scanning electron and light microscopy from the Lower Pliocene (Zone CN11 of Okada and Bukry 1980) of the South Caribbean Sea. The coccolith shows typical reticulofenestrid distal and proximal shields but the distal shield is surmounted by a cup-shaped structure formed from extensions of the inner and outer tube elements. A new genus is not introduced, although this structure is peculiar for reticulofenestrids. We base generic attribution on the distal shield morphology. The species occasionally has few slits between the distal shield elements. Attribution to the genera Reticulofenestra instead of Pseudoemiliania is discussed in detail.

R. calicis n. sp. is structurally similar to the modern Emiliania huxleyi var. corona and to Reticulofenestra maceria.

R. calicis n. sp., readily recognized under the light microscope in side view, has a short stratigraphic range. If the species proves not to be under strong ecological control, it will constitute a new biostratigraphic marker for subdivision of the R. pseudoumbilicus Zone.

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