THE MULTIPLE ORIGINS OF THE PLACENTAL CARNIVORES

The various groups of carnivorous placental mammals3, living and extinct (except the toothed whales and sometimes the seals), have been in the twentieth century almost always placed in a single order, the Carnivora. In the few exceptions a group usually regarded as a suborder of the Carnivora, the "Creodonta," is elevated to ordinal rank. All the groups of the Carnivora (and "Creodonta," if separated) have been thought to come from a family of relatively primitive Paleocene and early Eocene (and now late Cretaceous: Sloan and Van Valen, 1965) mammals, the Arctocyonidae, which forms the base of the "Creodonta." This grouping, and the ph'ylogeny on which it is based, dates from the work of Cope and Schlosser 80 and 90 years ago and that of Matthew about 60 years ago. It is shown in Figure 1, derived from Romer (1945), and may be compared with my present view of the relationships of the same groups (Figure 2). Several proposals since 1940 have affected the arrangement to some degree. Gazin (1941), following a suggestion of Simpson (1936), showed that the Phenacodontidae, the family on which the Condylarthra was based, arose from the Arctocyonidae. (This. is the case cited by Simpson (1953) where different species of one genus [Protogonodon, which