In order to better explain the construction of the C. leptoporus animated phylogenetic scenes, a brief summary of the taxonomic concept and the morphometric measurements that were developed in Knappertsbusch (2000) is provided below. The motivations of the entire study, descriptions of core and sample locations, measurement techniques and precision are discussed in detail in that reference and are not repeated here. The calculations of numerical ages of all samples follows the integrated chronology of Berggren et al. (1995) and is also documented in that reference.

Coccospheres of Calcidiscus leptoporus (Figure 1) are covered by circular to sub-circular calcite platelets. On their surfaces (=distal side) these coccoliths are ornamented by sinistrally imbricated elements with sinusoidally shaped sutures. Using the diameter of the coccoliths and the number of elements per cycle in these shields, various authors have distinguished several morphological variants of C. leptoporus in both living and fossil assemblages (Bukry and Bramlette 1969; Janin 1981; Baumann 1990; Knappertsbusch et al., 1997). The subspecific, and in some cases the specific, positions of these morphotypes in the diameter versus elements space are, however, still not yet firmly established because patterns of accepted variation within these morphotypes exhibits substantial overlap. As a result, additional criteria must be applied for reliable diagnosis. Calcidiscus macintyrei, for example, which is a very large extinct morphovariant, is considered a separate species by stratigraphers, whereas other investigators treated it as an informal morphovariant (Janin, 1981; Knappertsbusch et al. 1997; Knappertsbusch 2000).

The characterization of C. leptoporus by coccolith size and number of distal shields was, however, found useful for morphotype separation in C. leptoporus. This distinction was especially clear when contoured bivariate diagrams of coccolith frequencies were constructed (see example in Figure 2 and Figure 3). Based on this technique Knappertsbusch (2000) elaborated a taxonomic scheme with nine morphotypes from a global set of living, Holocene, and Miocene to Pleistocene assemblages (Figure 4). The interpretation of the stratigraphic distribution of these morphotypes led to the putative phylogenetic reconstruction of C. leptoporus from the Miocene to Recent shown in Figure 5.

The phylogenetic reconstruction obtained in this way was compared with a semi-continuous mathematical data model, that interpolated between coccolith densities per unit areas of diameter versus elements (=grid-cells, see Figure 3) in samples from one time-level to the next. This approach avoided application of the artificial classification scheme shown in Figure 4 (the details of this model are explained under "Approach 3" and in Figures 8 and 9 of Knappertsbusch 2000).