A “remarkable” meat-eating dinosaur that roamed North American 155 million years ago has been officially recognised - 30 years after first being discovered.
Palaeontologists described the carnivore Allosaurus jimmadseni in the journal PeerJ after seven years of painstakingly preparing its bones for study.
The two-tonne beast - a large type of Allosaurus - had three razor sharp claws at the end of each arm - and 80 serrated teeth for cutting flesh.
Named Allosaurus jimmadseni, it was up to 29 feet long and like T Rex, it ran on two legs but its longer arms may have made it a better hunter.
Believed to have lived between 157-152 million years ago, A. jimmadseni is the geologically-oldest species belonging to the allosauridae family from the Jurassic and Cretaceous periods.
The species was named after Utah’s state palaeontologist James H Madsen Jr, who died in 2009.
The species evolved at least five million years before its cousin Allosaurus fragilis – which was first described in 1877.
Dr Mark Loewen, a research associate at the Natural History Museum of Utah in the US, who also led the study, said: “The skull of Allosaurus jimmadseni is more lightly built than its later relative Allosaurus fragilis, suggesting a different feeding behaviour between the two.”
While it is believed there are anywhere between one and 12 species of Allosaurus, the researchers said their study officially recognises only two species – A. Fragilis and A. jimmadseni.
Dr Brent Breithaupt, a regional palaeontologist for the Bureau of Land Management in Wyoming, US, said: “This exciting new study illustrates the importance of continued palaeontological investigations on public lands in the west.
“Discovery of this new taxon of dinosaur will provide important information about the life and times of Jurassic dinosaurs and represents another unique component of America’s heritage.”