New Dinosaur Species Which is close relative with triceratops (1)

New Dinosaur Species Which is close relative with triceratops, the regaliceratops, discovered in Canada

New Dinosaur Species Which is close relative with triceratops (1)

An artist’s reconstruction of the new horned dinosaur Regaliceratops peterhewsi. Illustration: Julius T. Csotonyi/Royal Tyrrell Museum, Drumheller, Alberta.

When fossil experts first clapped eyes on the skull, it was clearly from a strange, horned dinosaur. When they noticed how stunted the bony horns were, its nickname, Hellboy, was assured.

The near-complete skull of the 70 million-year-old beast was spotted by chance 10 years ago, protruding from a cliff that runs along the Oldman river south of Calgary in Alberta, Canada.

Painstakingly excavated, cleaned up and measured since then, the fossilised remains have now been identified as a relative of the three-horned triceratops, and the first example of a horned dinosaur to be found in that region of North America.

New Dinosaur Species Which is close relative with triceratops (2)

The near-complete regaliceratops skull, first spotted protruding from a cliff in Alberta, Canada. Photograph: Sue Sabrowski/Royal Tyrrell Museum, Drumheller, Alberta

Like triceratops, the new species was a herbivore. But it sported a more impressive shield, or frill, at the back of its skull, decorated with large triangular and pentagonal plates. The extraordinary features led researchers to name the new species Regaliceratops peterhewsi, a reference to the impressive crown-like frill, and to Peter Hews, a Calgary-based geologist who first spotted part of the skull jutting from the rockface in 2005.

Researchers came up with the Hellboy nickname long before they had liberated the full skull from the cliff face. The main reason was that the rock the fossil was embedded in was incredibly hard, making excavation a hellish, and years-long, task. That job was made even tougher because the Oldman river is a protected fish-breeding ground, meaning the scientists had to erect a dam at the site to prevent debris from the excavation falling into the river.

“It was a coincidence, but when we noticed that the skull had these short horns over the eyes, that really solidified the nickname,” Caleb Brown at the Royal Tyrrell Museum of Paleontology in Alberta told the Guardian. In the Hellboy comics and movies, the eponmymous demon grinds his horns to stumps with an electric sander to help him fit in with mere mortals.

But the horns of the dinosaur tell a more interesting story. Triceratops belonged to a group of horned dinosaurs called chasmosaurines. These had a small horn over the nose and two larger horns over the eyes. And while regaliceratops is definitely a chasmosaurine, it has a long nose horn and puny horns over its eyes. These features, opposite to those characteristic of triceratops, are seen in a different group of horned dinosaurs, called centrosaurines, which were extinct by the time regaliceratops came along.

The bizarre mix of features is an example of convergent evolution, where one species evolves bodily characteristics that arose separately in other species through the course of prehistory. Brown and his colleague, Donald Henderson, describe the creature’s remains in Current Biology.

“This is a really interesting new dinosaur,” said Steve Brusatte, a vertebrate paleontologist at Edinburgh University. “It’s a close relative of triceratops, but it’s horns and skull frill are very different. They look a lot more like other types of horned dinosaurs that lived earlier in time, which went extinct before triceratops thrived.

“What it’s indicating is that there was massive convergence between the horns and frills of those horned dinosaurs that were thriving during the final few million years before the asteroid hit and killed off the dinosaurs. Because this new dinosaur is one of the latest surviving horned dinosaurs, living at a similar time as triceratops, it is also telling us that horned dinosaurs remained quite diverse right until the end. To me, this is a strong hint that these dinosaurs were at or near the top of their game when that asteroid fell out of the sky,” he said.

Illustrations of Stegosaurus with wide plates and tall plates are seen in a handout image from Evan Saitta, a student at Britain's University of Bristol.  REUTERS/Evan Saitta/Handout via Reuters

How do you tell a boy dinosaur from a girl dinosaur?

Illustrations of Stegosaurus with wide plates and tall plates are seen in a handout image from Evan Saitta, a student at Britain's University of Bristol.  REUTERS/Evan Saitta/Handout via Reuters

Illustrations of Stegosaurus with wide plates and tall plates are seen in a handout image from Evan Saitta, a student at Britain’s University of Bristol. REUTERS/Evan Saitta/Handout via Reuters

(Reuters) – For extinct creatures like dinosaurs known only from fossils, it is notoriously difficult to differentiate the males from the females of a species because sex distinctions are rarely obvious from the skeletons.

But in the case of the well-known Jurassic dinosaur Stegosaurus, a study published on Wednesday may provide a handy how-to guide on telling the boys from the girls based on the shape of the big bony plates protruding from its back.

Stegosaurus, which roamed the western United States about 150 million years ago, was a large, four-legged plant-eater with two rows of plates along its back, as well as two pairs of spikes at the end of its tail to clobber predators.

The largest Stegosaurus species reached about 30 feet (9 meters). The species in this study, Stegosaurus mjosi, measured roughly 21 feet (6.5 meters).

A Montana Stegosaurus “graveyard” contained fossils of several individuals, with plates coming in two distinct varieties: some wide, others tall. The wide ones reached sizes 45 percent larger in surface area than the taller ones, which were nearly 3 feet (90 cm) high.

“Males typically invest more into their ornamentation than do females, so the larger wide plates were likely from males,” said Evan Saitta, a 23-year-old paleontology graduate student at Britain’s University of Bristol whose study appears in the journal PLOS ONE.

“The broad, thin structure of the plates and their positioning on the back of the animal suggests that they were used in sexual display, analogous to the tail of a peacock. The broad, wide plates likely made a continuous display surface along the animal’s back to attract mates, like a billboard.”

To test whether the plate differences were instead because some individuals were young and others old, CT scans and microscopic analyses were performed that showed the bone tissue had ceased growing, meaning both varieties came from full-grown adults.

Anatomical and other differences between the sexes of a single species, like a male lion’s mane or a male deer’s antlers, are called sexual dimorphism.

Sexual dimorphism examples have been proposed in other dinosaurs, but many scientists find those inconclusive. Saitta said the Stegosaurus plates may be “the most convincing evidence for sexual dimorphism in dinosaurs to date.”

University of Bristol paleontologist Michael Benton added, “It suggests that many dinosaurs used sexual display, as birds and mammals do today, usually the males displaying or mock fighting to attract attention of females.”

(Reporting by Will Dunham; Editing by Sandra Maler)