ANCIENT MAMMAL LODGED IN RESIN COULD YIELD ANSWERS TO EVOLUTION.
A bundle of bones encased in hardened tree sap shows that ancient mammals can be preserved in amber, two paleontologists announced Thursday.
In a letter to the British journal Nature, David Grimaldi and Ross MacPhee of the American Museum of Natural History described the first authenticated example of a small mammal trapped in amber, or hardened tree resin. Paleontologists have found spiders, insects and even tiny frogs preserved in the substance - but few experts expected that anything as large as a quarter-pound, insect-eating, shrewlike creature could be preserved.
``The mammal is a serendipitous find,'' said Raul Cano, an amber expert at California Polytechnic State University in San Luis Obispo.
The discovery suggests that mammals trapped in amber could help answer evolutionary questions about the group, which began its rise after the dinosaurs' extinction about 65 million years ago.
The animal probably didn't get stuck in amber the way that bugs do, MacPhee said. Insects usually step into a glob of sticky sap as it's oozing out of a tree and are unable to escape. As sap continues to flow out of the tree, the insects are covered and permanently encased.
The process is so effective that paleontologists have found, trapped in amber, perfectly preserved insects that are more than 100 million years old. Some of the samples have even yielded DNA that can be analyzed to answer questions about insect evolutionary history.
But the preservation of the mammal wasn't that elegant, MacPhee said. Rather than a perfectly preserved specimen, what the paleontologists have is a slightly crushed and deformed skeleton.
``What we figure is that this thing was already reduced to a skeleton, or close to it, when the tree resin dropped on it,'' said MacPhee, curator of mammalogy at the New York City museum.
In fact, it looks as if the mammal had already been eaten by an owl when it was preserved in amber. Because owls don't chew their food, the birds have to dispose of undigested bones and hair by vomiting them in small pellets.
``We think it is owl lunch barfed back up and later preserved by the resin,'' MacPhee said.
He estimates that the skeleton is between 20 million and 29 million years old. In the past few years, MacPhee has found monkey, rodent and sloth fossils of about that age in the Dominican Republic.
In his letter, MacPhee says the discovery of the amber-encased insect-eater reinforces his theory that mammals arrived on the large Caribbean islands between 30 million and 40 million years ago, probably on a land bridge created by temporarily lower sea levels.
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|Publication:||Daily News (Los Angeles, CA)|
|Date:||Apr 14, 1996|
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