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 But relatively soon afterward, a plucky critter that looked like a
beaver was thriving, exemplifying the resilience of the mammals that
would arise from the margins of the animal kingdom to become Earth's
dominant land creatures.
Scientists on Monday announced the discovery in northwestern New
Mexico's badlands of the fossil remains of Kimbetopsalis simmonsae,
a plant-eating, rodent-like mammal boasting buck-toothed incisors
like a beaver that lived just a few hundred thousand years after the
mass extinction, a blink of the eye in geological time.
Kimbetopsalis, estimated at 3 feet long (1 meter), would have been
covered in fur and possessed large molar teeth with rows of cusps
used to grind down plants.
Asked what someone's impression of Kimbetopsalis might be, New
Mexico Museum of Natural History and Science curator of paleontology
Thomas Williamson said, "They would probably think something like,
'Hey, look at that little beaver! Why doesn’t it have a flat tail?"
It lived in a lush area of forests, rivers, streams and lakes as
Earth's ecosystems began to recover from the catastrophe that ended
the Cretaceous Period and opened the Paleocene Epoch.
"It's larger than almost all of the mammals that lived with the
dinosaurs, and also had a plant-eating diet, which few if any
dinosaur-living mammals had. It shows just how quickly mammals were
evolving in that brave new world after the asteroid cleared out the
dinosaurs," said paleontologist Steve Brusatte of Scotland's
University of Edinburgh.
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"Mammals, which actually originated hundreds of millions of years
earlier at the same time as the dinosaurs, now found themselves in
an empty world, and they took advantage," Brusatte added.
Kimbetopsalis was a member of a mammalian group called
multituberculates that resembled rodents although they were not
closely related. Although now extinct, disappearing about 35 million
years ago, multituberculates were extremely successful, having lived
for 120 million years.
"Mammals survived the mass extinction, but they did not pass through
unscathed," Williamson said. "I think it would be better to describe
those survivors as being lucky. A few just happened to have been
adapted to survive the catastrophe, probably because they were
small, could hide in burrows and eat bugs."
The research was published in the Zoological Journal of the Linnean
Society.
(Editing by Eric Walsh)
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