Ancient Dinosaur Used Spiked Hand to Steal Eggs in the Dark
Sixty-seven million years ago, a small dinosaur crept through the darkness. This dog-sized creature approached the nest of a larger dinosaur. Its target was a large egg. The tiny thief had a special tool for this meal. It possessed a multitooled forelimb with a giant claw, two side digits, and a set of spikes.
These features were ideal for clutching the smooth surface of an egg. Researchers described this bizarre hand and the dinosaur it belonged to in December. Their findings appeared in the Proceedings of the Zoological Institute of the Russian Academy of Sciences.
A Unique Fossil Discovery
The team named the species Manipulonyx reshetovi. The spike-covered hand of Manipulonyx, meaning "manipulating claw," surprised scientists. Stephen Brusatte, a paleontologist at the University of Edinburgh, expressed amazement. He was not involved in the study.
"I've honestly never been more flabbergasted by any dinosaur fossil," Brusatte said. At first glance, he wondered if it could be "some kind of lobster larvae or starfish."
A Russian paleontologist unearthed a fragmentary skeleton of the animal in 1979. The discovery occurred in the Gobi Desert in Mongolia. The area's rocks date back to the late Cretaceous period about 67 million years ago.
This region was once a swampy river delta. It was home to diverse dinosaurs including armored ankylosaurs and dome-headed pachycephalosaurs. The Tyrannosaurus rex cousin Tarbosaurus also lived there. Scurrying underfoot were Manipulonyx dinosaurs.
Belonging to a Peculiar Family
Manipulonyx belonged to a family of diminutive dinosaurs known as alvarezsaurids. These animals possessed tiny forearms that ended in one large digit with a hook-like claw. The other fingers were much smaller.
That led some scientists to mistake the dinosaurs for flightless birds. How alvarezsaurids used their peculiar paws has incited debate. Some scientists think the mysterious mitts dug up insects like modern anteaters.
Others have argued that the long-legged dinosaurs could not reach the ground because of their short arms. They instead ate eggs. Adding to the confusion was the absence of delicate carpal bones in the animal's wrists.
These bones connect hands and forearms. Alexander Averianov, a paleontologist at the Zoological Institute of the Russian Academy of Sciences, felt excited. He came across the Manipulonyx specimen and realized the animal's arms were intact.
Superb Preservation Reveals Details
"The Manipulonyx skeleton is unique in its superb preservation," said Averianov, lead author of the new paper. "It is the only known specimen to show articulated carpal bones, reduced side fingers and hand spikes."
Manipulonyx's hand spikes were likely encased in keratin. This is the same material found in fingernails. One spike was on the inside of the dinosaur's hand. Another wedged between its large finger and its smaller side fingers. The third spike jutted out of the reptile's palm.
According to Michael Pittman, a paleontologist at the Chinese University of Hong Kong, these spikes were "totally unexpected." Pittman was not involved in the study. His assessment was based on other alvarezsaurid fossils.
In 2011, Pittman helped describe Linhenykus, an alvarezsaurid that possessed only one finger. He said the new fossils were just as surprising. This is "quite a feat for a dinosaur group already known for its strange arms and hands."
Egg-Stealing Hypothesis Gains Support
Averianov believes that other alvarezsaurids closely related to Manipulonyx had barbed hands. This feature has yet to turn up in the fossil record. He and his colleagues posit that Manipulonyx used the spikes and the side fingers to grip slippery egg surfaces.
They then used their large claw to crack the shells. The scientists suspect that Manipulonyx raided nests at night. Alvarezsaurids most likely possessed large eyes and good hearing for such activities.
Alvarezsaurids appear to have had a penchant for pilfering eggs from oviraptorosaurs. This group of dinosaurs had parrot-like beaks. They were once thought to be egg snatchers too.
Further research suggested that oviraptorosaurs were instead doting parents. They vigilantly guarded their nests. Another alvarezsaurid skeleton in China was found alongside bits of eggshell from an oviraptorid dinosaur.
The original label attached to the Manipulonyx specimen also notes nearby fossilized eggshells. Brusatte thinks the egg-snatching hypothesis is plausible. But he wouldn't rule out the dinosaurs using their hands for something even stranger.
"All I'm confident in saying is that they weren't using these arms and hands to fly or swim," he said. "Beyond that, let your imaginations run wild."
