Palaeontologists believe they have settled a debate surrounding the largest ever carnivorous dinosaur.
The researchers at the University of Portsmouth say their discovery of 1,200 dinosaur teeth "proves beyond reasonable doubt" that Spinosaurus was an "enormous river-monster".
Its dental remains accounted for 45% of those found in a prehistoric river, they said.
The findings have been published in the Cretaceous Research journal.
Spinosaurus fossils were found in large numbers at the site of an ancient river bed in Morocco, which flowed through the Sahara Desert 100 million years ago.
The scientists said their discovery meant the 15-metre (49ft) long, six-tonne dinosaur was not a land-based predator but a largely aquatic one.
This backs up the latest findings made by researchers in April, following the analysis of a Spinosaurus tail.
David Martill, professor of palaeobiology at the university, said: "We know of no other location where such a mass of dinosaur teeth has been found in bone-bearing rock.
"The enhanced abundance of Spinosaurus teeth, relative to other dinosaurs, is a reflection of their aquatic lifestyle.
"An animal living much of its life in water is much more likely to contribute teeth to the river deposit than those dinosaurs that perhaps only visited the river for drinking and feeding along its banks."
Spinosaurus aegyptiacus remains were first discovered about 100 years ago in Egypt.
They were moved to a museum in Munich but destroyed during World War Two.
Since then only fragments of Spinosaurus bones have been found, including a giant fossil in 2014.
Spinosaurus has enjoyed wider popular notoriety since 2001, when it bested a Tyrannosaurus rex in Jurassic Park III.