Calciosoleniaceae (coccolithophorids) from the Galapagos Islands: unmineralized components and coccolith morphology in Anoplosolenia and Calciosolenia , with a comparative analysis of equivalents in the unmineralized genus Navisolenia (Haptophyceae = Prymnesiophyceae)

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Abstract
Coccolith morphology in Anoplosolenia brasiliensis (Lohm.) Defl. and Calciosolenia aff. murrayi Gran from the Galapagos Islands has been investigated three-dimensionally mainly by means of scanning electron microscopy used with a tilting stage to supplement transmission electron microscopy and light microscopy. The rhomboid coccoliths in both genera are shown to be concave proximally with a central groove and convex distally with a central ridge. An unmineralized membrane with characteristic peripheral striations is demonstrated on the proximal face of the rhomboids in both genera, with less complete evidence suggesting a second, patternless, membrane on the distal face of the coccoliths in Calciosolenia . Other newly described details are illustrated, and the existence of left-right reversal in some of the observations recorded in the standard literature is noted. When this is corrected, the uniform orientation of coccoliths in position on the cell surface in both genera is discussed in a preliminary way. Finally, comparisons are made with the wholly unmineralized cells of Navisolenia aprilei Lecal, ex Leadbeater and Morton, recently described in the literature, which resemble Calciosolenia so closely in salient features of cell shape, scale shape, scale arrangement and aspects of surface patterning, that a phyletic connection seems unavoidable. Some possible taxonomic consequences of these findings are discussed in a preliminary way in relation to the known antiquity and specialized condition of all members of Calciosoleniaceae though the need for further information on all of them is stressed.