Siluriformes constitute an important monophyletic group of mainly freshwater fishes (Fink and Fink, 1996). Presently, there are about 35 families with over 2,000 species in all continents except Antarctica (Lundberg, 1993; Nelson, 1994); however, at least in the Eocene, they also inhabited Antarctica as well (Grande and Eastman, 1986). A small number of catfishes (most of the ariids and many of the plotosids) are marine and some species of other families can enter brackish waters (Nelson, 1994). Pre-Cenozoic catfishes are extremely rare outside of South America.

One of us (G.V.R.P.) has...

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