Louis Dollo, a French born,
Belgian paleontologist is perhaps best known for supervising the reconstruction of Iguanodon fossils discovered in an
underground mine in 1878; and for an idea which says, evolution is not
reversible. The idea became known as Dollo’s Law and suggests that once
organisms loose a structure during the course of evolution it will not
re-evolve. Like most such “laws,” it was doomed to failure due to exceptions.
John Wiens, Stony Brook
University, has now documented the re-evolution of
mandibular teeth in the marsupial frog, Gastrotheca
guentheri. It has been long known that frogs do not have teeth on the
mandible – with the exception of some frogs of the family Hemiphractidae. Weins
used a time-calibrated amphibian phylogeny that demonstrates frogs lost their
mandibular teeth 230 million years ago (MYA), only to have Gastrotheca gunetheri (or an ancestor) re-evolve mandibular teeth 5
to 17 MYA. George Kingsley Nobel recognized that Gastrotheca had true teeth, he wrote “The most remarkable
osteological feature of the Hemiphractinae is the redevelopment of true teeth
on the dentary….Such teeth do not occur in any other Sallientia…”
Weins’ results provide an exceptionally well documented example of
re-evolution, demonstrating that mandibular teeth were lost in the ancestor of
all living frogs and then re-evolved in the hemiphractid species G. guentheri. Weins points out that the re-evolution of
mandibular teeth may not surprise herpetologists, but notes this example has
been ignored in the recent literature on Dollo's law. The time involved from
the loss of teeth to their re-evolution in Gastrotheca – an absence of at least
225 million years (and probably longer) is remarkable.
For a news story on this article follow this link.
1931. The Biology of the Amphibia. McGraw-Hill, New York .
Wiens, J. J. 2011. Re-evolution
of lost mandibular teeth ion frogs after more than 200 million years, and
re-evaluating Dollo’s law. Evolution,
Labels: evolution, Gastrotheca, mandibular teeth, marsupial frogs