Article: Large mammals once dined on dinosaurs
From: Robert Karl Stonjek (rstonjek_at_bigpond.net.au)
Date: 01/14/05
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Date: Fri, 14 Jan 2005 19:16:44 +0000 (UTC)
Large mammals once dined on dinosaurs
18:00 12 January 2005
Jeff Hecht
When the dinosaurs ruled the world, the mammals hid in the shadows, daring
to grow no bigger than shrew-like insectivores that hunted at night. Or so
we thought.
Two stunning new fossils from China have overturned this preconception. Not
only did large mammals live alongside their giant reptilian cousins, but
some were big and bold enough to go dinosaur hunting.
Named Repenomamus giganticus and Repenomamus robustus, the sturdily built
mammals lived in China about 130 million years ago, around 65 million years
before we thought their kind inherited the Earth. At 1 metre long, R.
giganticus was big enough to hunt small dinosaurs, and a newly discovered
fossil of its smaller cousin, R. robustus, died with its belly full of young
dinosaur.
This totally overturns the notion of dinosaur-age mammals as tiny and
nocturnal, says vertebrate palaeontologist Hans-Dieter Sues of the
Smithsonian Institution in Washington DC, US. "Apparently some mammals could
grow much larger than anyone had thought was possible."
In another role reversal, those comparative mammalian giants may have
affected dinosaur evolution by preying on them, adds palaeontologist Anne
Weil of Duke University in Durham, North Carolina, US.
Filling niches
Mammals and dinosaurs evolved from different groups of comparable-sized
reptiles during the Triassic, which ran from 248 to 206 million years ago.
In the conventional picture, dinosaurs filled the niches for large
plant-eaters and predators, relegating mammals to the marginal niches that
are now home to shrews and rodents. So large mammals could evolve only after
the dinosaurs died 65 million years ago.
And while a handful of teeth and other fragmentary remains hinted that a few
large mammals may have lived alongside the dinosaurs, little was known about
them. No one had found a reasonably complete skeleton of a Cretaceous mammal
as large as R. giganticus, says Yaoming Hu at the American Museum of Natural
History in New York, US.
R. giganticus and the new fossil of R. robustus come from an area of China's
Lianoning province famed for its feathered dinosaurs. R. giganticus was a
short-legged but powerful animal with fearsome teeth, similar to a large
modern Tasmanian devil or a honey badger. "I wouldn't want it coming after
me," Weil told New Scientist
Full Text at NewScientist
http://www.newscientist.com/article.ns?id=dn6874
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Robert Karl Stonjek
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