First Known One-Fingered Dinosaur Found in Mongolia

A tiny one-fingered bug-eating dinosaur is a first for paleontologists. The beast marks the only dinosaur known to date to sport just a single digit on each hand.

That doesn't count modern birds, which are dinosaurs that have modified the lone claws on each of their hands into part of their wings.

The evolutionary loss of fingers is often seen in the predatory dinosaurs, or theropods. For instance, while early theropods had four fingers on each arm, T. rex only had two. The newly discovered dinosaur kept only its index fingers. [Read: Fossil Solves Mystery of Dinosaur Finger Evolution]

The new raptor is named Linhenykus monodactylus — Linhenykus means "claw from Linhe," the city in Inner Mongolia near where the specimen was found in 2008, and monodactylus means "one-fingered." This mini-predator lived roughly 84 million to 75 million years ago, and would have been just 1 pound (450 grams) in weight and maybe 15 inches (40 centimeters) long from head to tail.

The researchers have not only faced sandstorms at the site, but a hailstorm, too. "Forty to 50 degrees Celsius (104 to 122 degrees Fahrenheit), no shade, and you are getting pelted with ice," researcher David Hone, a paleontologist at the University College Dublin in Ireland, told LiveScience. "Quite a bizarre situation!"

The claws of Linhenykus were likely used for digging — its arm bones had adaptations "very similar to what you see in moles," Hone said. These included attachment points on the bone for powerful muscles and bone shapes that could exert the kind of leverage needed for digging.

Linhenykus probably lost the use of its other fingers because "there is really not much that a multi-clawed hand would have done," Hone added. "That one giant finger and claw is doing all of the work and the others are just kind of there."

This new dinosaur likely once lived in open, scrubby desert, which could have been verdant around rivers. "Its diet would be termites and possibly ants and probably any small insect if it came across it," Hone said. The dinosaur's major predators would have likely included distant relatives such as Velociraptor.

The scientists detailed their findings online Jan. 24 in the Proceedings of the National Academy of Sciences.

Charles Q. Choi
Live Science Contributor
Charles Q. Choi is a contributing writer for Live Science and He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.