by: Erin Wayman.
The long-lost cousins of
today's camels once roamed the high Arctic, browsing open forests in regions
that are near-barren landscapes today. That's the conclusion from an analysis
of the fragmentary remains of an ancient leg bone unearthed on Canada's Ellesmere
Island, which lies just west of northern Greenland. The find also adds to the
tantalizing clues about how these moose-sized, presumably shaggy progenitors
fit into the camel family tree—a lineage that today boasts only two species of
true camels but includes plenty of South American relatives such as llamas,
alpacas, guanacos, and vicuñas.
Today, camels inhabit arid
regions stretching from northern Africa to the interior of Asia. But ancestors
of the creatures first evolved in North America about 45 million years ago,
says Natalia Rybczynski, a paleontologist at the Canadian Museum of Nature in
Ottawa. Some of these animals crossed a land bridge from what is today Alaska
to eastern Siberia—and that meant they were living, even thriving, at latitudes
where few mammals can now subsist.
The fossils, dug up by
Rybczynski and her colleagues in recent field seasons, came from a gravel-rich
layer of sediments laid down more than 3.4 million years ago. The 30 or so bits
of bone, none more than 7 centimeters long, have suffered much since they were
entombed: Ice sheets have scoured Ellesmere Island several times in the past
few million years, and today's freeze-thaw cycles continue to splinter fossils
into ever-smaller fragments, Rybczynski says. The sizes and shapes of the bone
bits suggest that they came from a tibia (a lower leg bone), but from those
clues alone it's impossible to identify the species or group of mammal the
fossils came from. However, some bone features clearly indicate that the
creature was an artiodactyl, a broad group that today includes deer, cows, and
camels.
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