March 4, 2009—Nearly 200 million years ago, a meat-eating dinosaur plopped down on the edge of a lake and rested its arms, palms slightly facing inward, in an almost yoga-like pose (seen above right in an artist's conception).
The fossil handprints of this "crouching dinosaur" (above left, shown with white arrows) were discovered in 2004 in St. George, Utah. They are the first known prints made by a meat-eating dinosaur's front limbs.
"We got lucky with this one [sitting] on a slope," which brought its hands closer to the ground, said study author Andrew Milner of the St. George Dinosaur Discovery Site at Johnson Farm.
The find has shaken up paleontologists' understanding of how dinosaurs evolved into modern birds.
The imprints suggest all two-legged meat-eaters, or theropods, carried their arms in an inward-facing, birdlike posture during the early Jurassic period, much earlier than this trait was thought to have developed.
The find also boosts some paleontologists' beliefs that theropods didn't ever carry their short arms palms-down—as Tyrannosaurus rex is often depicted doing in movies and books.
In fact, the newfound dinosaur would have dislocated its shoulders if it kept its palms down, said Milner, whose research appeared today in the journal PloS One.