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Catfish beats Columbus to America

So did the ancestors of American Indians, of course, but a catfish seems to have beat them by about 50 million years. "Discovery of African roots for the Mesoamerican Chiapas catfish, Lacantunia enigmatica, requires an ancient intercontinental passage" by John Lundberg, John Sullivan, Rocio Rodiles-Hernandez, and Dean Hendrickson, was published in Proceedings of the Academy of Natural Sciences of Philadelphia.

This aptly-named catfish species, recently discovered in Mexico, appears to be most related to catfish in Africa. A family tree based on DNA and calibrated using fossils suggests that the last common ancestor of the Mexican and African species lived 75 to 94 million years ago. This was after continental drift separated Africa from South America.

How did the fish get to Mexico? It swam, presumably. The problem is that catfish are freshwater fish. The authors suggest that partial melting of polar ice during the Eocene may have made the Arctic Ocean warm enough and fresh enough for the ancestors of the Mexican catfish to survive a long ocean swim.


For those needing to know more, this paper is available as a free pdf download from a link on the Chiapas catfish Wikipedia page (as is the earlier scientific description of this fish).

If this polar migration explanation is accurate, we ought to be able to find catfish fossils in Canada. Has anybody done this?

I wouldn't expect fossils of catfish that died during the crossing, because there wouldn't have been many of them. But if they landed in North America and slowly spread south, there could be fossils, as one of the authors suggests below. I would also think that, if the Arctic ocean was fresh for very long, there could be fossils of various freshwater species in the ocean sediments.

Hi...I am one of the authors of the paper. The question about fossils is a good one. In the paper we consider different ways an African freshwater clade could have made it to Mesoamerica. We weigh the different possibilities given our estimate of how old the Chiapas catfish lineage is (based on a calculation from DNA differences and fossils). Our suggestion that this lineage arrived in Mesoamerica via North America in the Late Cretaceous or Early Tertiary (either via Beringia or across the freshened North Atlantic) does predict the presence of fossils of this group in North America. To date, no catfish fossil from North America has been identified as a close relative of the Chiapas catfish, but our knowledge of the catfish fossil record is still very incomplete.

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