Mighty Big Cretaceous Bird Tracks

["M. J. Murphy" <mjm@pathcom.com>]

This story came from the Nando Times, URL given below:



Father-daughter team find important fossil in
  Alaska

  Copyright © 1999 Nando Media
  Copyright © 1999 Scripps McClatchy Western Service

  By NATALIE PHILLIPS

  ANCHORAGE, Alaska (September 22, 1999 12:01 a.m. EDT
  http://www.nandotimes.com) - Some 70 million years ago, when the North

  Slope was crawling with dinosaurs, a flock of large, crane-sized birds

  landed on a muddy shelf of what is now the floodplain of the Colville
  River. They were there to feed.

  Over the years, warm temperatures became seasonal, the Atlantic
  and Arctic oceans began to take shape, the dinosaurs disappeared,
  and modern plants and mammals started to appear. But the muddy
  bird tracks survived, turning to faint but permanent scars on a slab
of
  sandstone.

  This summer, Kevin May and 14-year-old daughter Lizzie of Fairbanks
  set out on a three-week journey in search of traces of the
  prehistoric past. They traveled 250 miles down the Colville River in
  two motorized rafts.

  Near the end of their trip, they beached their boats near the
  confluence of Anaktuvuk River and walked along the shore. There
  they found what they coveted. With water lapping around all sides
  was a raised piece of sandstone covered with what the untrained
  eye might see as chicken tracks.

  They found what appears to be the first site of multiple prehistoric
  bird tracks ever documented in Alaska. May said they probably date
  from the late Cretaceous period, 65 million to 97 million years ago.

  "I have a feeling as soon as this comes out, we are going to have
  people from all over the world contacting us," said May, a researcher
  at the University of Alaska Museum in Fairbanks.

  A dinosaur tracks expert in Colorado agrees.

  "It's not surprising to find bird tracks, but I would have to say
these
  would be the most far-north examples of bird tracks known," said
  Martin Lockley, a paleontologist at the University of Colorado in
  Denver. "And if the tracks are really the size of a sandhill crane,
then
  this is really significant."

  Today's sandhill cranes are among the tallest birds in the world and
  have a 6-foot wingspan.

  "We just haven't found that large of bird in the Cretaceous period.
  We have lots of plovers, sandpipers and killdeers. It would be pretty
  rare to find anything so large back in the Cretaceous period," May
  said. "To some extent we are not quite sure what all existed at that
  time."

  May plans to present his preliminary findings this week at the
  American Association of Advancement of Science's Arctic Science
  Conference, being held at Denali National Park and Preserve.
  Eventually he will publish a paper on the tracks, which will be
subject
  to academic study, interpretation and debate before they find their
  place in history.

  Dinosaur ichnology, the study of fossil footprints, is a relatively
  undeveloped science but has been catching on during the past
  decade. Paleontologists have come to realize that tracks and track
  sequences can help fill in unknown blanks about what dinosaurs were
  like and how they lived.

  Sometimes a creature's speed can be estimated with measurements
  of the spaces between tracks - the stride - and a formula developed
  by one paleontologist. Tracks help determine whether the dinosaur
  was part of a herd. They also can help scientists figure out feeding
  patterns.

  "Before, geologists were not looking for tracks. Now they have their
  eyes tuned to find them," Lockley said. The new focus on tracks has
  triggered a renaissance in the search for dinosaur remnants, he
  added.

  "It's a fairly new area," added Anne Pasch, a geology professor
  emeritus at the University of Alaska-Anchorage. "Tracks used to be
  considered oddities."

  Pasch said the Mays' find is "very significant. It's wonderful."

  Their discovery indicates there was "a very complete ecosystem, not
  just a bunch of occasional visitors to the North Slope," she said.
  "There was a community that lived in that environment."

  May went on fossil expeditions along the Colville River in summer 1997

  and 1998. In 1998, the team found and documented for the first time
  dinosaur trackways on the Arctic coastal plain. The team's work
  turned up evidence of seven different meat- and plant-eating
  dinosaurs, including the oval-shaped tracks of an unknown species,
  and tracks that show the pebbly texture of skin. Skin impressions are
  a very rare find. Pasch was one of the leaders of that expedition.

  But May felt the time to look for tracks was too limited.

  "So this summer we specifically went looking for tracks, the broadest
  variety of tracks we could find," May said as he laid down a latex
  sheet the size of a throw rug that he and daughter Lizzie made of
  some of the tracks they found.

  Tracks tell a story, May said. "We've got plenty of bone material from

  dinosaurs and some bone material from birds. But you can find tracks
  in places where bones would never be preserved. Tracks give you an
  insight into behavior."

  He and his daughter spent three weeks looking for tracks. They found
  six new early Cretaceous dinosaur track sites, which date back 97
  million to 144 million years. They found at least four sizes of bird
  tracks, ranging from 5/8 inches up to 4 inches, that indicate there
  might have been a diverse bird population living in the Arctic in the
  late Cretaceous. They also found what looks like several deposits of
  coprolite - fossilized dinosaur excrement, what some just call
  paleopoop.

  They loaded their boat with more than 800 pounds of rock slab
  specimens, but then the boat would hold no more. So in many cases
  they made latex imprints. That was Lizzie's job. First she painted a
  layer of shellac over the tracks. Then she painted several thin layers

  of pale green latex, allowing two hours between coats to dry.
  Between the multiple layers of latex, she put layers of cheesecloth to

  keep the latex from shriveling.

  May said if they came across a rock slab that appeared important but
  fragile and about to be washed away, they packed it out. Otherwise
  they preferred to leave the specimens in place and make latex
  imprints, which can be rolled up and carted off. "They're bomb-proof,"

  he said.

  One of the 3-by-5-foot latex sheets they brought back shows the
  tracks and what appears to be bird-feeding traces. The tracks were
  found on rock that appeared not to have shifted from weathering or
  other forces but to be the exact place the birds touched down
  millions of years ago.

  Natalie Phillips writes for the Anchorage Daily News.