Paleontologists have discovered in Niger bones of two massive meat-eating dinosaurs that may have picked over the same prey, much as modern-day lions and hyenas do.
University of Chicago paleontologists Paul Sereno and Stephen Brusatte named one of the dinosaurs Kryptops palaios, or "old hidden face," because of a horny covering over its face, they wrote in the scientific journal Acta Palaeontologica Polonia.
The other, they named Eocarcharia dinops, or "fierce-eyed dawn shark," for its razor-sharp teeth and bony brow.
Both were about 25 feet (7.62 meters) long and stood 7 feet (2.13 meters) high at the hip. Kryptops had a short snout with teeth better for gnawing, leading the scientists to believe he was more of a scavenger.
Eocarcharia's brow was so pronounced that Sereno believes it was used for head-butting rivals to win over potential mates.
"The only thing I can think of is they were smacking each other with it," Sereno said.
The creatures lived at a time when land bridges connected Africa to India and even Antarctica, which was then a temperate home to dinosaurs. But Africa later became isolated and its dinosaurs followed unique evolutionary paths scientists have just begun to uncover.
"This is an important slice in geological time, and we don't yet fully comprehend how dinosaurs on the southern continents were evolving then," said Peter Makovicky, curator of dinosaurs at the Field Museum, who was not part of the Chicago team.
Makovicky called the new discoveries "an important data point toward a deeper understanding of what happened."
Sereno's group found both new species during a 2000 expedition to the Niger desert. They found bones from about a dozen new species, and stumbled across one of the richest archaeological sites that has been found in the region.
"We have not released even half of all that we found there," Sereno said.