Nov 7, 2009 6:11 pm US/Mountain
Paleontologist: Too Many Dinosaurs Called Unique
BILLINGS, Mont. (AP) ―
A noted Montana paleontologist's theory could wipe scores of dinosaur species from the Earth's history and modern text books.
Jack Horner, director of the Museum of the Rockies in Bozeman, says up to a third of dinosaur species identified by humans never existed. Some dinosaurs were incorrectly classified as unique species when they represent juveniles or subadults of already known species, he said.
"There are skeptics out there, as usual, which is good," said Horner. "But we're in the business where skeptics have to have evidence. We have a lot of evidence for our hypothesis."
Horner recently published research, co-authored with Mark Goodwin of the University of California, Berkeley, in the peer-reviewed online science journal PLoS ONE.
Horner said he and Goodwin focused on dome-headed dinosaurs and theorize that those dinosaurs went through vastly different forms of head hardware as they aged. Horner said the changes occurred so dinosaurs could signal species difference to other dinosaurs as well as their sexual maturity.
"I have to admit it seems pretty weird that they go through such a drastic change," Horner said. "But we're seeing it across a wide range."
He said the dinosaur skulls appear so different at various ages that they were incorrectly classified as unique species rather than young dinosaurs. CAT scans of dinosaur skulls backs up the theory, he said.
The researchers studied the skulls of three dinosaurs classified as three different species: Pachycephalosaurus wyomingensis, Stygimoloch spinifer and Dracorex hogwartsia.
The examination included CAT scans that offered microscopic analysis of slices of bone, which Horner said led he and Goodwin to conclude all three skulls were from the same species at different stages of life.
"We had pretty good ideas this was going on but the CAT scan really nailed it," Horner said. "Before the CAT scan we could only guess at it, or you could drop it on the floor."
Changes in bone configuration in the dinosaurs' heads is from bone redistribution, not bone loss, the researchers said.
"The strength of it is there are multiple lines of evidence," said Goodwin.
Horner said scientists need to re-evaluate the catalog of dinosaurs while considering growth.
"People have the tendency to look at the difference between things rather than the similarities," he said.
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Information from: Billings Gazette, http://www.billingsgazette.com
(© 2009 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)
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