Two enormous heads arrayed with horns are the first striking images of a pair of newly-discovered dinosaur species announced today.

The ornate heads belong to kosmoceratops richardsoni and the utahceratops gettyi, two species of dinosaur found in southern Utah's Grand-Staircase-Escalante National Monument.

The research team describe them in the online journal PLoS ONE.

Dr Eric Roberts is one of the scientists involved in the discovery and is now based at James Cook University in Townsville in north Queensland.

He says both kosmoceratops and utahceratops were plant-eating inhabitants of the long lost continent of Laramidia about 76 million years ago.

"The two dinosaurs are relatives of the famous triceratops but they are about 10 million years older," he said.

Dr Roberts says it is particularly exciting because they are among the first of many dinosaur discoveries being made in the region.

"The area we're working in is yielding a whole slew of other dinosaurs as well," he said.

"This pair is from a whole amazing range of discoveries, from other dinosaurs to other mammals."

Elaborate horns

The two new dinosaurs have a much more elaborate array of horns than the more familiar triceratops, with the smaller of the two, kosmoceratops, bearing 15 of different shapes and sizes.

It is the most ornate dinosaur head yet discovered - 'kosmos' is Latin for ornate.

The discoverers speculate that rather than being used for fighting, the horns may have been for decoration and advantage in courtship displays, as well as to deter mating rivals.

The utahceratops does not have as many horns, but is distinguished with a massive head - its skull measuring 2.3 metres long.

It is said to resemble a giant rhino with a supersized head.

Lost world

The lost continent of Laramidia was a land mass approximately the size of Australia that existed during the Late Cretaceous Period - 99.6 to 65.5 million years ago.

It formed when a large inland sea divided what is now North America into Laramidia (western half) and Appalachia (eastern half).

The northern part of Laramidia - present day Montana and Alberta - is a rich source of dinosaur discoveries - including the triceratops and the infamous tyrannosaurus rex.

Dinosaur fossils have been found as far south as Texas and New Mexico.

Palaeontologists have only been studying the fossils of the 1.9 million-acre Grand Staircase-Escalante National Monument of the southern region for a decade, but believe it still holds a rich source of new discoveries.

"The surprising find is that what we're finding is that it turns out that a lot of the different dinosaurs are very closely related in age," Dr Roberts said.

"This was a relatively large land mass, but to have all these different dinosaurs living in relatively the same age is amazing."

Dr Roberts says the next step is to work out how so many different dinosaurs co-existed at the same time in a relatively restricted region.

"It's really quite incredible that we're seeing this large number of different taxa living apparently at the same time," he said.

"It is something that starts to prompt some interesting ecological and environmental questions."