ANCHORAGE (AP) -- Scientists have discovered fossilized footprints left 55 million years ago by primitive mammals and cranelike birds in an ancient forest bordering what is now the Talkeetna Mountains.
The animal tracks -- including several sets found in sequence -- offer the first evidence that land mammals lived in Alaska during the period right after the extinction of the dinosaurs, according to Kevin May, University of Alaska Museum fossil expert.
He documented the finds this past summer in a project coordinated by the University of Alaska Anchorage.
''These animals are extremely rare,'' said Anne Pasch, UAA paleontologist and professor emeritus. ''There aren't many of this age anywhere in the world.''
The tracks appear to have come from five different species -- two mammals and three birds -- and range in width from 1-inch to almost 10 inches. The largest, with three to five blunt toes, could have been made by a mammal the size of a grizzly bear. Others contained footpads and claws that suggest a doglike carnivore.
The location of the animal tracks will not be publicized to protect their scientific value, Pasch said.
''We don't want people trying to look for them and remove them,'' she said. ''The main reason is that these things need to be documented (in place), and we don't want people destroying information.''
The tracks are subtle and difficult to identify, often little more than a vague depression or cast, according to May and Pasch. Others overlapped each other.
''One rock has about 11 prints on it,'' May said. ''I'm thinking about four steps with both fore and hind feet.''
''There's a lot of work ahead to prove that's what they are,'' Pasch said. ''I think there might be some people who might question this. ... It's not nearly as easy as finding a skeleton.''
The tracks first came to light on Memorial Day 1999. May and his stepdaughter Lizzie were looking for fossils in the Talkeetna foothills when, ''She said, 'You'd better come look at this,' and sure enough, they were impressions in a good surface.''
Until now, the nearest fossil record of these primitive mammals had been found in North Dakota and Texas, according to May, a researcher and fossil preparer at the University of Alaska Museum at Fairbanks.
''It extends the range of early mammals quite a distance across North America,'' May said. ''It was an ecosystem that supported animals, and probably in great abundance.''
In what may be the most intriguing aspect of the find, the tracks represent the only evidence that mammals lived in the lush, subtropical forests that rimmed the Pacific Ocean from California through Alaska to Japan during the early Eocene when mammals first arose, Pasch said.
''This is another piece of this whole ecosystem,'' she said.
Over the past three seasons, Pasch and her students have been documenting an extraordinary collection of plant fossils in the same general area. In and around old coal digs north of Sutton, Pasch and her students have collected hundreds of fossilized leaves from 43 ancient species and outlined an entire natural community.
In what may be one of the most extensive petrified forests in the world, they've recorded fossilized trees and stumps -- some possibly buried in place during a late fall flood, Pasch said. Several of the trees are now on display on the UAA campus in a geological ''rock garden.''
''It's a world-class fossil site,'' Pasch said. ''It's one of the most unique places in the world.''
As one of Pasch's undergraduate students, May unearthed a partial skeleton of a dinosaur in 1994 that lived in what is now the Talkeetna's 90 million years ago. May has studied footprints and fossils of dinosaurs during subsequent expeditions to the Colville River on Alaska's North Slope, and in Alberta and the Yukon Territory.
Like the prince in a fossil Cinderella, May plans to take rubber casts of the prints this winter to Outside museums, where he'll try to match them to the feet of prehistoric animals in their collections.
''We absolutely do not know what made these tracks,'' May said. ''There's no way to tell at this point.''
Still, the tracks already suggest a few likely candidates.
An extinct mammal that might fill the largest tracks was the bear-sized coryphodon -- a small-brained omnivore that probably shares ancestry with modern ungulates.
''It was not anywhere as specialized as a black bear, and not anywhere near as smart,'' Pasch said.
Two others had one to three well-defined toes of cranelike birds. One impression nearly 10-inches long resembled the footprint of an extinct flightless bird as large as an emu.
''We're reasonably certain we know which groups of animals made some of the tracks,'' May said. ''It's in the ball park. The feet are the right size.''
(Distributed by The Associated Press)
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