The 72 million-year-old rhino-sized plant-eater Coahuilaceratops magnacuerna was an ancestor of the famous three-horned Triceratops.
Like other horned dinosaurs, or ceratopsids, it had a large bony plate behind its head which would have acted as a shield.
Coahuilaceratops’ most notable feature are the two enormous horns that jut out from above its eyes.
Fossil bones of an adult animal, which weighed four to five tons, measured around 22ft, and stood six to seven feet tall at the shoulder and hip, were recovered from a site in the state of Coahuila, southern Mexico, in 2003.
Remains of a juvenile were also found nearby.
Scientists believe the horns were most probably used in mating contests rather than to fight off predators.
Lead researcher Dr Mark Loewen, from the Utah Museum of Natural History in Salt Lake City, said: ‘The horned dinosaurs are an extraordinary example of vertebrate evolution.