A small fossil animal that survived in what may have been among the
harshest climates on Earth 73 million years ago has been found by
paleontologists working in northern Alaska.
The Late Cretaceous mammal was described by the researchers, who were led
by Jaelyn Eberle of the University of Colorado Boulder, in a report that was
released this month in the Journal of Systematic Palaeontology.
They gave it the scientific name Sikuomys mikros, which is derived from the
Iupiaq word "Siku" for "ice" and the Greek terms "mys" and "mikros" for
"mouse" and "little," respectively.
Its title is appropriate. The little ice mouse was really a member of the
Gypsonictopidae family of extinct mammals, not a mouse, although it was
unquestionably small. The fuzzy creature, believed to weigh 11 grams, or
less than an empty metal drink can, may have resembled a modern-day
shrew.
Additionally, it spent the whole year in northern Alaska, which at the time
was located far further north, above the Arctic Circle. There, the ice mouse
most likely endured up to four months of nonstop winter darkness and
subfreezing temperatures.
According to Eberle, a professor in the Department of Geological Sciences
and curator of fossil vertebrates at the CU Museum of Natural History,
"These guys probably didn't hibernate." They were active throughout the
year, digging underground or under leaf litter to eat anything they could
get their teeth into, most likely insects and worms.
She and her colleagues had to work just as hard to find the extinct
animals; they were only able to identify the new species from a small
collection of teeth, each about the size of a grain of sand.
Eberle remarked, "I always enjoy working at the very edge of the planet."
You never know what you'll find, but you can be sure it will be something
fresh.
According to study co-author and director of the University of Alaska
Museum of the North Patrick Druckenmiller, those tiny fossils are opening up
a new window for research into prehistoric Alaska.
"Northern Alaska was home to an ecosystem unlike any on Earth today, 73
million years ago," he added. It was a polar forest full with birds, tiny
animals, and dinosaurs. These creatures were created to survive in a highly
seasonal environment with icy winters, snow, and up to four months of total
winter darkness.
traveling north
It's not always simple to go to the extremities of the Earth.
The fossils were discovered by the researchers, who also included
paleontologists from Florida State University and the University of Alaska
Fairbanks, in sediments along the banks of the Colville River, which is
located close to the Beaufort Sea on Alaska's northern shore. The crew flies
by bush aircraft or snowmobile to the location, which is a portion of the
so-called Prince Creek Formation, from Deadhorse, Alaska, a distance of
around 75 miles.
Gregory Erickson, a co-author of the study from Florida State University,
stated that the research his team is doing is exposing a "Lost world" of
species that have adapted to the Arctic. In the presence of extreme seasonal
climatic swings, Prince Creek acts as a natural test of these animals'
physiology and behavior.
The new study also included co-authors from the University of California,
Berkeley, including the late William Clemens.
The only animal fossils still found in the area are a few teeth and bits of
jaws, unlike dinosaurs from the same era that left behind massive bones. The
crew gathers soil from the riverbanks in buckets in order to retrieve these
priceless specimens. The muck is washed away in the lab, and the remaining
material is sorted under a microscope.
Eberle remarked, "You look under the microscope and see this perfect little
tooth." It is really little.
Protection underneath
Those adorable tiny teeth of the ice mouse have given rise to a charming
little enigma.
At higher latitudes and in colder climates, species of several families of
mammals on Earth tend to become larger. It appears that the ice mouse and
its related species follow the opposite tendency. Paleontologists have
discovered closely similar species that were three to five times bigger than
Sikuomys mikros and lived thousands of kilometres to the south.
Eberle speculates that the ice mouse's diminutive size was a result of its
lack of food during Alaska's winter months.
Today, shrews exhibit a similar behavior, she observed. "The theory is that
if you're really small, your energy and food requirements are lower."
It's possible that Sikuomys Mikros spent the chilly months underground in
Alaska. In the end, living underground may have benefited creatures like the
ice mouse. The severe circumstances that followed the meteorite smash that
wiped off the dinosaurs 66 million years ago may have been more hospitable
to burrowing animals.
Provided by
University of Colorado at Boulder
