BEIJING (AFP) - One of the world's top fossil hunters unveiled a previously unknown gigantic, chicken-like dinosaur Wednesday that may change evolutionary theory on prehistoric animals. The remains of the animal, thought to have weighed 1,400 kilogrammes (3,100 pounds), was discovered in a freak find by Xing Xu in the Erlian basin in Inner Mongolia, an area rich with fossils, the scientist told AFP. The new species, named the Gigantoraptor erlianensis, is the biggest bird-like dinosaur ever found and at a height of five metres (17 feet) is comparable in size to the famous Tyrannosaurus, Xing said. The 85 million-year-old creature was 35 times heavier than other known similar species, and is thought to have had a beak and sporadic patches of feathers, according to a paper to be released in UK science journal Nature on Thursday. "If you saw a mouse as big as a pig you would be very surprised, it is the same when we found the Gigantoraptor," Xing, from the Chinese Academy of Sciences in Beijing, told reporters on Wednesday. "The new dinosaur is much larger than its relatives of the similar species. We have spent a year to confirm its features and characteristics." The find may contradict an evolutionary theory that as carnivorous dinosaurs got smaller they became more birdlike, the Nature paper said. Xing discovered the first femur of the Gigantoraptor in 2005 during the shooting of a documentary about one of his previous finds. The crew asked him to demonstrate how he finds fossils and during the shot, he chanced upon a section of the femur, or thigh bone. "We randomly picked up a bone on the surface," Xing said in an interview with AFP. "We initially thought it was from the same species as we had discovered before, but minutes later we realised it was from a meat-eating dinosaur. "This big size is very unusual for a meat-eater and only a Tyrannosaur is of similar size." Xing's team then embarked on further digs which uncovered an extensive collection of bones, followed by a lengthy verification process, leading to the release of the latest paper, which suggests the huge 11-year-old was only partly grown. Sections of the film where Xing discovered the first bone were shown during a press conference Wednesday here in Beijing, where several parts of the species, including its skull were on display. "We found it was a very bird-like, feathered dinosaur -- like an enormous chicken," Xing told AFP earlier. "It is the largest beaked dinosaur, and would have had no teeth in its mouth." Xing is one of the world's leading fossil hunters and has discovered more than 20 new species at various sites across China. In 2001 he was embroiled in controversy over the discovery of a fossil believed to be the "missing link" between dinosaurs and birds, which tests revealed to be a clever fraud. Xing authenticated the find in 1999, but was also part of the team that began expressing doubts a few months later after he found that the tail on fossils were suspiciously similar to those of a different species. Forensic scanning found that the fossil -- which had been sold to unwitting US collectors by Chinese traffickers -- was simply a thin stone slab coated with grout and glued to a jigsaw of 88 fragments of rocks and fossilised bones. China is rich with archaeological sites, but suffers from an illegal trade in real and fabricated dinosaur bones, previous reports have said.