Conodonts meet cladistics: Recovering relationships and assessing the completeness of the conodont fossil record

A numerical cladistic analysis of the conodont family Palmatolepidae has be en undertaken to determine the applicability of the technique to group-wide systematic revision. Results suggest a new hypothesis of relationships tha t is considerably more parsimonious than trees compatible with existing hyp otheses of relationships, or trees that are even loosely constrained strati graphically. This may occur either because the fossil record is incomplete, because taxon sampling for the cladistic analysis is low, or because the m ost parsimonious trees approximate the true tree less well than do stratigr aphically-constrained trees (or because of a combination of these factors). Although more taxa and more characters would be preferable in choosing bet ween these possibilities, the tree derived solely from morphological data i s adopted. Thus, stratigraphic data can be used to test hypotheses of relat ionships and construct phylogenies; hypotheses of relationships can be used to test the completeness of the conodont fossil record. Existing schemes o f classification within the Palmatolepidae are rejected because most groups within them are either polyphyletic or paraphyletic. A new scheme is prese nted. Character changes: suggest correlated, progressive and mosaic evoluti on within the Palmatolepidae. Parsimony analysis of partitioned datasets in dicates that more phylogenetic information can be recovered from S rather t han P or M element positions, although data from all three positional group s are preferable to data from just one. Thus, multielement taxonomy is esse ntial to the resolution of conodont interrelationships.