THE ORDER CARNIVORA AND THE extinct order Creodonta include the most carnivorously adapted placental mammals, and they have been widely considered to be sister taxa, within the superorder Ferae (Fig. 8.1, Table 8.1). Except for a general dental similarity between them, however, there is surprisingly little evidence that they constitute a monophyletic group (e.g., Flynn et al., 1988). For example, although both groups have teeth adapted for carnivory, the carnassial teeth are not homologous in creodonts and carnivorans (Fig. 8.2). Possible synapomor-phies of the two orders include the presence of an ossified tentorium (a bony shelflike projection separating parts of the brain) and a few basicranial and tarsal similarities, but they are not very compelling (Flynn et al., 1988; Wyss and Flynn, 1993). There is also a close correspondence in postcranial osteology between various primitive carnivorans (miacoids) and creodonts, but as yet, none of the similarities has been shown to be synapomorphic, and most are thought to be primitive. Consequently the case for monophyly of a creodont-carnivoran clade is weak. Nevertheless, no preferable phylogenetic arrangement is obvious. Although possible relationships between Carnivora and other major clades (Pholidota, Lipotyphla, Primates, Chiroptera, and various ungulates) have been suggested, largely based on molecular evidence, none of these (except possibly Pholidota) is particularly persuasive either (Flynn and Wesley-Hunt, 2005).
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