"There simply are no tracks or real track-like features at this site," said Brent Breithaupt, director and curator of the University of Wyoming's Geological Museum in Laramie. Breithaupt led a group of scientists to the Vermilion Cliffs National Monument near Kanab a few weeks after U. geologists identified the site as a rich dinosaur trample surface dating to the early Jurassic. Their announcement piqued a great deal of public interest and they have no plans to retract their findings.
"The paper still stands. We had descriptions. We had comparisons. It was peer-reviewed. It's just we came up with an interpretation that not everyone agrees with," said Marjorie Chan, who co-authored the study that appeared in Palaios, an international paleontology journal.
Chan, a respected scientist who chairs the U. department of geology and geophysics, first saw the strange pockmarked surface, covering about 3/4 of an acre, in 2005.
She later directed graduate student Winston Seiler to the site in the Coyote Buttes North area to measure the rock's red colorations. Struck by the unusual nature of the holes, particularly tiny mounds around their rims, Seiler developed a detailed theory that the impressions were formed by dinosaurs frequenting what must have been an oasis in a vast desert. The study also identified possible tail drags in the rock.
"I'm not going to say I wasn't disappointed, but I'm looking forward to the next phase," said Chan, who announced the disagreement Friday. "We are open to dialogue and look forward to collaborating to resolve the controversy."
The two groups intend to study the site together and maintain there are no hard feelings between them.
"We're not trying to embarrass the U. We, as scientists, want to know the truth. Marjorie is the same way," said Alan Titus, a Bureau of Land Management paleontologist assigned to the Grand Staircase-Escalante National Monument. "It's nice that we didn't see it degenerate to name calling and program bashing."
Titus took part in the Oct. 30 site visit with Breithaupt, BLM geologist Rody Cox and Andrew Milner, of the St. George Dinosaur Discovery Site at Johnson Farm. Most of the holes appear to be too round to be animal imprints, they say.
"There was already widespread skepticism based on the shape, orientation, spacial distribution of the features that were being interpreted as dinosaur prints," Titus said. "Most were perfectly circular, rather than distinct toe-bearing prints. There were little holes nestled into big holes. There were things that didn't look like they would be related to trackways or to the behavior of animals."
Sauropods are a dinosaur species capable of leaving round footprints, but the long-necked behemoths had yet to evolve at the time the region's famous Navajo sandstone was deposited. But if it wasn't stomping animals, what formed the holes, which the geologists say are markedly different than the potholes typical of this sandstone?
"My suspicion is it's a unique rock fabric that is controlling the formation of these holes. We're seeing the solutioning of the rock rather than just effects of weathering," Titus said. "The fact that they grow into round shapes is due to the homogeneity of the rock."
The raised edges that struck Seiler could be the result of endolithic bacteria that clung to the tops of the holes and shielded the rims from the forces of erosion, Titus suggested. Meanwhile, on their hike to the "dance floor" last week, the paleontologists did observe likely dinosaur prints.
"There is no question dinosaurs were out there during the Jurassic, but there is a question about what gets preserved in the geological record," Chan said.
"Science is a dynamic process. We try to search things out. We didn't do anything wrong other than make an interpretation, but this is how science goes. It gets scrutinized."