Rat, got good news for you. One of your members are still alive.
Back from the dead
A few months after researchers on one team thought they had
discovered a new family of rodent, another group snatched their
glory by identifying the critter as a member of a family thought
long extinct.
Last year scientists described the body of a squirrel-like rodent
found for sale in a meat market in Laos. They believed it belonged
to a previously undescribed family and named it Laonastes
aenigmamus.
But they failed to fully inspect the fossil record. Upon closer
analysis of the creature's teeth, a second group of researchers
determined it was a member of the previously known rodent family
Diatomyidae.
So a family thought to have died out 11 million years ago is still
alive and kicking, the scientists report in the March 10 issue of
the journal Science.
Back from the dead
The discovery is an example of what scientists call the "Lazarus
effect," a situation when an animal known only through the fossil
record is found living.
Perhaps the best known example of the Lazarus effect is the
coelacanth, a lobe-finned fish discovered off the coast of South
Africa that scientists thought died out at least 65 million years
ago.
Most examples of the Lazarus effect in mammals, though, only go
back 10,000 years or so.
"It is an amazing discovery and it's the coelacanth of rodents,"
said study coauthor Mary Dawson of the Carnegie Museum of Natural
History. "It's the first time in the study of mammals that
scientists have found a living fossil of a group that's thought to
be extinct for roughly 11 million years. That's quite a gap.
Previous mammals had a gap of only a few thousand to just over a
million years."
Laonastes is currently in the process of being officially
reclassified in the Diatomyidae family.
Teeth truth
Diatomyidae were squirrel-sized rodents that lived during the
middle Tertiary period 34 million to 11 million years ago in
southern Asia, central China, and Japan. They also had highly
characteristic molar teeth and jaw structure, which is how the
researchers reclassified Laonastes.
A recently discovered fossil of Laonastes matched the "living"
specimen in skull shape and overall size. The only difference is
that the "living" specimen's teeth are slightly more pointed.
"It looks like possibly one of the things that's been changing in
family is improved cutting of vegetation," Dawson told LiveScience.
"But over 11 million years you'd expect some differences in the
structures."
Western scientists still haven't seen a living Laonastes specimen,
which will be critical in conserving what may be a threatened
species.
"Biologists need to get out there and find some living ones,"
Dawson said.
Finding living specimens and understanding how they live could be
key to determining why the rodents moved from central Asia into the
Indian subcontinent.
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