Different species and types of extant Calciosolenia are described in this paper. The two species C. murrayiGran 1912 and Anoplosolenia brasiliensis (Lohmann 1919) Deflandre 1945 were traditionally placed in separate genera, the main differences being in the presence or absence of spines in the apical part of the coccosphere. Recent work (Young et al. 2003) transferred A. brasiliensis into the genus Calciosolenia, due to the high similarity in coccolith morphology.
Within this paper, the varimorphic nature of both species is shown and the coccolith ultrastructure is described in detail, with the recognition of new diagnostic characters, such as the presence of spurs at the coccolith ends. Four different morphotypes are recognized within C. murrayi, based on the variability in central area structure; a further type shows affinity to both C. brasiliensis and C. murrayi, depending on the characters considered: this is defined as a new species, C. corsellii, and its taxonomic position is discussed.
These observations reveal a high morphological diversity within the Calciosoleniaceae, with complex relations between individual species.