for National Geographic News
Published January 19, 2010
Following in a giant dinosaur's footsteps could be fatal—but not for the reasons you might suspect.
Mysterious "death pits" holding the fossil skeletons of nearly two dozen small dinosaur species may actually be the 160-million-year-old footprints of an ancient behemoth, a new study suggests.
The first of three dino-filled pits was unearthed nearly a decade ago in northwestern China's remote Xinjiang region.
Inside the 3.5- to 6.5-foot-deep (1- to 2-meter-deep) depressions were the largely complete skeletons of several species of small theropods, bipedal raptors from the lineage that includes Tyrannosaurus rex.
The stacked fossils included Guanlong, or "crested dragon," a T. tex ancestor with a Mohawk-like head adornment. Limusaurus, also found in the pits, was a probable herbivore with an intriguing hand that some experts believe links dinosaur limbs to bird wings.
Even as scientists celebrated these rare fossil finds, a mystery remained: What created the death traps in which the animals were entombed?
Treacherous Tracks
Analysis of the rocks surrounding the dinosaur fossils shows that the unfortunate animals were stacked up inside in a mixture of volcanic mudstone and sandstone, say geologist David Eberth and colleagues, whose work was partially funded by the National Geographic Society.
"All of the geological data indicated to us that we're dealing with sediments that were originally very rich in fluids," said Eberth, of Alberta's Royal Tyrrell Museum. "These were never empty holes in the landscape."
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