Virginia Institute of Marine Science
Huelsenbeck (1994) identified three unsolved issues regarding the use of temporal information in the fossil record: (1) how goodness of fit between stratigraphy and phylogeny should be determined, (2) how the significance of this fit should be determined, and (3) how those results might be employed other than for description. With respect to goodness of fit, Huelsenbeck (1994) suggested that his stratigraphic consistency index (SCI) was both intuitively simple and not subject to the biases inherent in other stratigraphic indices. With respect to these prior indices (Gauthier et ai., 1988; Norell and Novacek, 1992), apparent biases are the result of a logical incompatibility of data types. These indices are simply the nonparametric Spearman correlation between rank stratigraphic age and rank position on a cladogram. The incompatibility stems from the fact that stratigraphic data are inherently linear whereas trees (and the genealogies they represent) are not so constrained.
Siddall, ME, Stratigraphic consistency and the shape of things (1996). Systematic Biology, 45(1), 111-115.