CONGRUENCE BETWEEN SUPERPOSITIONAL AND PHYLOGENETIC PATTERNS: COMPARING CLADISTIC PATTERNS WITH FOSSIL RECORDS

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Abstract
Abstract— As the only direct evidence of past organismic history, the fossil record has always figured importantly in the reconstruction of phylogeny. But the incomplete nature of the fossil record has also been cited as a basis for claiming that fossils play only a secondary role in developing phylogenetic hypotheses that encompass extant taxa. The reliability of fossil data in such applications is a function of the degree of fit between superpositional relationships and the sequence of phylogenetic events. Thirty‐eight vertebrate cases are examined for the fit between age data based on fossil first occurrences and phylogenetic results based on cladistic analysis. A general correspondence between superpositional and cladistic information is observed, although the degree of fit varies widely among cases. Horses, certain other ungulates, synapsids and basal archosaurs, which show very high correlations, are taxa characterized by an abundance of superpositional and cladistic data. Other groups, such as primates, show very poor correlations because certain major clades have either unreasonably short fossil durations or no fossil record at all. Correlations are also diminished when either fossil records or cladistic sequences are poorly resolved. In most cases, cladistic resolution was observed to exceed superpositional resolution. Correlations can be enhanced by more precise (e.g. radiometric) age dates, but these also place a high expectation on the fit between fossil first occurrence and cladistic results. Stratigraphic occurrence does not always provide a precise reflection of independently derived phylogenies, but the correspondence between age and cladistic information is remarkably high in a notable number of vertebrate examples.