A new species of carnivorous non-avian dinosaur, described in the latest issue of Cretaceous Research, could be the world’s smallest known dinosaur.
The tiny dinosaur, dubbed the "Ashdown maniraptoran," measures about a foot in length and was unearthed in the United Kingdom. It lived during the Lower Cretaceous, a period lasting from 145 million to 100 million years ago.
"It perhaps weighed as little as 200 grams (seven ounces)," co-author Darren Naish told Discovery News. "Like other maniraptoran theropods, this would have been a small, feathered, bird-like bipedal dinosaur with a fairly short tail, long neck, long slim hind legs, and feathered clawed forelimbs."
Naish is an honorary research associate in the School of Earth & Environmental Sciences at the University of Portsmouth. He and colleague Steven Sweetman analyzed the remains of the dinosaur, unearthed in the Pivensey Pit at Ashdown Brickworks, a site located northwest of Bexhill, East Sussex.
"The Isle of Wight, Surrey and East Sussex are all hotspots that frequently reveal new dinosaur species, which is not bad for a country that has probably been more thoroughly explored and studied than any other in the world," Naish said.
He and Sweetman conclude that the discovered fossil, a posterior cervical vertebra, likely belonged to a previously undocumented dinosaur species, since there are no named dinos that were maniraptoran theropods from the same-aged rocks from the same region.
Because they haven’t unearthed the dinosaur’s skull yet, the researchers cannot make firm statements about its diet.
"Based on other oviraptorosaurs and other small maniraptorans, it was perhaps an omnivore, eating small animals, including insects, as well as leaves and fruit," Naish said.
He added that, like most theropods, the Ashdown maniraptoran would have walked with its body and tail held in a horizontal position.
Its location adds to the growing body of evidence that during the Early Cretaceous, Southeast England and continental Europe were often home to similar dinosaurs and other animals.
"Land bridges that existed during part of the Early Cretaceous time also resulted in similarities between European dinosaurs and those of the U.S.A.," Naish continued.
Technically, the world’s smallest known dinosaurs are modern birds, since birds are dinosaurs. As such, the world’s smallest dinosaur is the Cuban bee hummingbird, which measures 2 inches long and weighs only about .063 ounces.
The Ashdown maniraptoran’s greatest rival for "world’s smallest non-avian dinosaur" at the moment is Anchiornis from China. It has been estimated at being 30 to 40 centimeters long. Where it exactly fell within that range remains unclear.
In recent years, quite a few tiny dinosaurs have been unearthed. One of the most memorable is Albertonykus borealis, a chicken-sized dinosaur that paleontologist Nick Longrich of the University of Calgary describes as "bizarre."
"They have long and slender legs, stumpy arms with huge claws and tweezer-like jaws," Longrich said in a press release. "They look like an animal created by Dr. Seuss."
Though small, this American dinosaur was powerfully built. It could rip open logs with its forelimbs to expose termites for consumption.
Longrich expects that researchers will discover additional new dinosaur species just by looking at "fossils we already have sitting in museum collections."
Both he and Naish, however, anticipate that more fossils from new species will continue to be unearthed. Naish and Sweetman are particularly hopeful that additional fossils will be found for the Ashdown maniraptoran. If so, the dinosaur’s nickname will be replaced with a proper scientific name.