PlanetCatfish.com

Silurus wrote:That's a tough one to answer.

One possibility that immediately comes to mind is that this reflects the history of the group. The fact that the most "primitive" catfishes (Diplomystes and, depending on who you follow, loricarioids and/or cetopsids) are South American would lend credence to this line of reasoning.

HH, do we currently have enough information to draw an approximate time line of the evolution of major catfish families? If so, can you give us a quick overview please?

Thanks,
Dinyar

The best answer to this question is to read Gayet & Meunier's chapter on the paleontology and paleogeography of catfishes in the two-volume catfish work.

Essentially, the catfish fossil record is still patchy. We have the earliest catfish fossils from the Albian (Early Cretaceous, ca. 112 mya) and then very little until a few more show up in the Paleocene (65-55 mya). By the Eocene (55-34 mya), most of the larger catfish families were already present, although some, like the Siluridae, have a fossil record that is more recent than that (the oldest definitive silurid fossils date from the middle Miocene, 16-12 mya).

Because of this patchiness, it is hypothesized that most of the major radiations in catfishes actually took place before the Cenomanian (Mid Cretaceous 100-94 mya).

It would take too long to list the oldest fossils for each family here, but the Gayet & Meunier chapter provides a good review.