INCORPORATING FOSSIL TAXA INTO PHYLOGENETIC ANALYSES OF MODERN CLADES: THE CASE OF PROPHAETHON

In 1899, new avian fossil material was recovered from the London Clay Formation (Lower Eocene) of England that was later described by C.W. Andrews as a new pelecaniform (Aves: Pelecaniformes) species, Prophaethon shrubsolei. Further preparation of the holotype in the 1970s at the British Museum of Natural History revealed new features of the taxon, which led to the conclusion that Prophaethon represented a new family within a monotypic order. The newly erected Prophaethoniformes was described as a missing link between the avian orders Charadriiformes, Procellariiformes, and Pelecaniformes rather than a close relative of the extant pelecaniform genus Phaethon (tropicbirds) as was previously hypothesized. Recent work has placed the Eocene bird at various nodes within a pelecaniform order, but doubts of the monophyly of this clade and lack of an extensive morphological dataset with which to develop hypotheses of pelecaniform relationships have confounded attempts to accurrately portray the phylogenetic affinities of Prophaethon. Here, I describe the results of a new cladistic analysis that seeks to describe the phylogenetic relationship between extant members of Pelecaniformes and Prophaethon. Morphological characters were defined and coded for nine extant genera of Pelecaniformes and the holotype specimen of Prophaethon shrubsolei. Character polarity was assessed by use of outgroup comparisons with Eudyptes (Sphenisciformes), Oceanodroma (Procellariiformes), Balaeniceps (Ciconiiformes), and Scopus (Ciconiiformes). A phylogenetic tree was derived using parsimony by use of the standard analytical software package PAUP Version 4.06b for Macintosh. All 149 characters were unordered, and a single most parsimonious tree was produced with a length of 425 steps, a retention index of 0.4914, and a consistency index of 0.3765. Prophaethon was placed within a monophyletic Pelecaniformes as the sister-taxon to a clade composed of Phaethon, Sulidae, Phalacrocoracidae, and Anhingidae. A clade containing Fregata and Pelecanus was found to be the sister-group of a clade composed of Prophaethon and the assemblage described above.