A Palaeontological Puzzle Solved?
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."
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.