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A Palaeontological Puzzle Solved?

Keith Thomson

The Devonian fossil Palaeospondylus gunni is one of paleontology's enduring enigmas. At 20 to 60 millimeters in length, it is just large enough to show that it is a fish, but not much more. Within 10 years of its discovery by two amateur collectors, the cousins Marcus and John Gunn, hundreds of specimens had been collected from the Achannaras slate quarry in Caithness, Scotland. Equally quickly, rival scholars eagerly and acrimoniously assigned it to every possible class and order. By 1903, the debate became so heated that Bashford Dean (curator both of Ichthyology and Herpetology at the American Museum of Natural History and of Arms and Armor at the Metropolitan Museum of Art) concluded in frustration: "Professor [Thomas Henry] Huxley, the astute morphologist, is perhaps to be felicitated in having had no traffic with it." He urged that it be put aside "where it will do the least harm."

Figure 1. <em>Palaeospondylus gunni</em>Click to Enlarge Image

Of course, Dean was ignored. Retreat is unusual among paleontologists, who always love a puzzle and rarely back away from a good fight. And now it seems that the problem with Palaeospondylus was not just in the fossils but in the pal(a)eontologists. Most early authors were determined to make Palaeospondylus into something very important from the evolutionary sense: an ancient kind of jawless fish, a new line of jawed fish, or a tantalizing "missing link" between ancient placoderms and sharks. For the purpose of their arguments, therefore, the greater the mystery—the more different it was from other fishes—the better.

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