A nine-ton block of sandstone that was pulled from a Utah mountain late last year holds the biggest fossil trove ever found of the giant predatory dinosaur known as Utahraptor. Covered in feathers, with a huge sickle claw on each second toe, Utahraptor looked like a pumped-up version of the Jurassic Park star Velociraptor.
The fossils might help resolve a long-standing debate about whether these predators hunted in groups. In the Jurassic Park films, velociraptors were shown cooperating to chase down prey, an idea based at the time on several predators that had been found alongside an herbivore. The new fossils may help confirm whether the silver screen got it right.
Scientists have found the remains of six Utahraptor dinosaurs in the rock so far, and more may be trapped there.
If the dinosaurs died together, they might provide some long-sought evidence of group hunting. The densely packed dinosaurs (in some places, fossils are stacked three feet thick) may have died at different times as they blundered into quicksand, or perhaps they died together in a social supper gone horribly wrong.
The remains were excavated in a massive effort that has spanned more than a decade, led by Utah state paleontologist James Kirkland.
The recent finds include never-before-seen bones that are already changing scientific views of the Utahraptor anatomy.
"We're really going to have a different view of this guy," Kirkland says. Part of the emerging picture is that while young Utahraptor dinosaurs were lightly built and turkey size, Kirkland explains, the adults were heavily muscled, "Arnold Schwarzenegger" versions.