Meeting Abstract

P2.213  Saturday, Jan. 5  Is Paranthropus monophyletic? Incorporating modular relationships in a cladistic analysis CORBIN, K.M.*; ALEMSEGED, Z.; Univ. of California, San Diego; California Academy of Sciences kcorbin@ucsd.edu

The three species of “robust” australopithecine, east African Paranthropus aethiopicus and P. boisei and south African P. robustus, have extremely derived masticatory systems for heavy chewing. Various studies have characterized the group as monophyletic, polyphyletic, or paraphyletic. The derived masticatory complex is often cited as being more prone to homoplasy than other craniodental features used in analyses. Many analyses have excluded masticatory features as a conservative test of the position of these three species, but few have considered characters that are developmentally or evolutionarily integrated, and thus not valid independent characters for a cladistic analysis. In this study, characters were amassed from the literature and missing data were filled in with specimens from the California Academy of Sciences Anthropology and Mammalogy collections. Cladistic parsimony analyses were run with PAUP* 4.0 in several configurations: with all characters; with characters related to specific masticatory traits collapsed into single characters; with integrated characters collapsed; and with both masticatory and integrated characters collapsed. In all analyses, “robust” australopithecine monophyly was maintained with excellent bootstrap support and consistency indices. The relationship of the basal “gracile” australopithecine species to the robust australopithecines was not resolved. A monophyletic origin for Paranthropus suggests that sometime in its evolutionary history, P. robustus migrated from east to south Africa, where basal species P. aethiopicus and sister species P. boisei lived.