Discussion of Phylogenetic Relationships
Siluriformes is clearly monophyletic as indicated by several complex anatomical synapomorphies (Fink & Fink, 1981, 1996) including modification of the upper jaw to support and move a pair of sensory barbels, and locking fin spines.
Approximately 436 genera and over 30 families of catfishes are recognized. Although there is general agreement on the broad outline of the higher level phylogeny of catfishes many questions remain. The southern South American Diplomystidae are the plesiomorphic sister group of the remaining catfishes or Siluroidei (Grande, 1987). Within the Siluroidei, the middle Eocene Hypsidoris (Hypsidoridae) from North America is the primitive sister taxon of all other catfishes or Siluroidea (Grande, 1987).
Two of the largest nominal families, the South American Pimelodidae and the African-Asian Bagridae have been vaguely portrayed as the "ancestral" groups for the Old World and Neotropical catfish radiations. It is possible or likely that the pimelodids and bagrids are paraphyletic (Mo, 1991; Pinna, 1993), although within each family monophyletic subgroups have been diagnosed (Mo, 1991; Pinna, 1993; Lundberg et al. 1991; Bailey and Stewart, 1984).
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