By Helen Briggs
Science reporter, BBC News
Fossils of a massive dinosaur unearthed a decade ago in the Republic of Niger, Africa, have been recognised as belonging to a new species.
Scientists say Carcharodontosaurus iguidensis was one of the largest meat-eaters that ever lived, rivalling T. rex in size and ferocity.
The 95-million-year-old fossils have been kept in a Chicago laboratory for several years, awaiting classification.
A student stumbled on the remains and realised they were important.
"It really is a fascinating animal - it was one of the largest meat eaters that lived on the planet," said Steve Brusatte, now an MSc student at the University of Bristol. "It's a new species - it is something totally different."
Strange and scary
The dinosaur had a skull about 1.75m long housing huge jaws armed with teeth the size of bananas.
It was part of a "very weird ecosystem" of huge bipedal carnivorous dinosaurs that inhabited the Saharan Cretaceous landscape.
"It was a 13m long predator that still had to watch its own back because something bigger was out there - an animal called Spinosaurus," Brusatte told BBC News.
Also known as the spine lizard because of its distinctive fin-like spines, Spinosaurus grew to 18m long, and lived alongside a third mighty carnivore - the 9m high Abelisaurid theropod.
"It was a very strange, very scary community at that time," he added.
The fossils were discovered in Niger in 1997 on an expedition led by the prominent fossil hunter Paul Sereno from the University of Chicago.
The jawbone of a closely related species has been found
Brusatte - who was 13 at the time - did not take part in the expedition but came across the remains while studying in Chicago.
While cataloguing the skull and neck fossils, he noticed that they showed a number of differences from similar Carcharodontosaurus specimens found in Morocco.
This placed them in a species of their own - named iguidensis after the region of central Niger from where they came.
Remains of similar members of the family have been described before but were lost to science in the early 20th Century.
"The first remains of Carcharodontosaurus were found in the 1920s, but they only consisted of two teeth which have since been lost," said Brusatte.
"Other bits of Carcharodontosaurus were found in Egypt and described in the 1930s, but these were destroyed when Munich was bombed in 1944.
"Since then a skull of Carcharodontosaurus saharicus turned up in the Moroccan Sahara, and was described a decade ago. So as you can see, evidence for this dinosaur is very rare."
The research, published in the Journal of Vertebrate Paleontology, sheds light on a peculiar time in history when the world was warm and wet, covered in shallow seas.
"The dinosaur seems to have evolved because these shallow seas divided up the land so it led to different groups of dinosaurs in different places - that has implications for how life reacts to high temperatures and high sea levels," explained Brusatte.
Dr Angela Milner, Deputy Keeper of Palaeontology at London's Natural History Museum, said the new find demonstrated that very large carnivorous dinosaurs were more widely distributed in Africa than previously suspected.
"It may be that these giants arose by allopatric speciation, whereby biological populations are physically isolated by a barrier, in this case a seaway, and evolve in reproductive isolation," she said.
"If the barrier breaks down later, individuals of the populations can no longer interbreed. This is a well recognised phenomenon in living animals but the same 'rules' almost certainly applied in the remote past as well. However, that hypothesis can't be tested with ancient fossils!"