Two fossils of a puny, horny-faced, seven-pound, four-legged creature found recently in China are turning out to be early ancestors of Triceratops, the 10-ton, tanklike vegetarian with three mighty horns.
Approximately 130 million years old, the new, two-foot-long dinosaur, Liaoceratops (pronounced lee-ow-SAIR-a-tops) was barely evolved from the days its own ancestors ran on two hind legs. It is described for the first time in an article co-authored by Field Museum paleontologist Peter Makovicky in the British science journal Nature published Thursday.
Chinese paleontologists found complete skulls and partial skeletons of both a juvenile and an adult Liaoceratops in a limestone formation in China’s Liaoning province that is proving to be one of the world’s great dinosaur burial grounds.
“The neat thing about this animal is that it is one of the smallest plant eating dinosaurs that we know of,” said Makovicky. An adult Liaoceratops was perhaps a foot tall and two-to-three-feet long, he said..
Makovicky, a world authority on neoceratopsians (dinosaurs with horns on their faces), was asked by the Chinese Academy of Sciences to study the two fossils and is the lead American author of the Nature article.
From humble beginnings 130 million years ago like Liaoceratops, the neoceratopsians thrived and evolved into ever larger animals for the next 65 million years.
Triceratops was the last of the neoceratopsians and perhaps the greatest one, arising 68 million years ago. One of the most familiar dinosaurs, Triceratops had a bigger skull than any other land-based animal before or since, made all the more prominent by three facial horns and a huge, spreading, armorlike neck frill.
Liaoceratops’ facial features are barely noticeable, Makovicky said.
“Liaoceratops don’t have the typical horns of ceratopsians, which grow out above eyes and on the nose,” he said. “Instead, they have subtle beginnings of cranial ornamentation protruding on each cheek, and a somewhat expanded frill, though a small one, nothing as prestigious as those on Triceratops.
“We know a lot about late members of this group. Now with Liaoceratops, we’ll get to know something of the early members.”
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Their mouths, he said, are designed so that they could nip off plants they fed on–conifers, gingko trees and horsetails–with their beaks.
Rows of teeth farther back in their mouths “met edge-to-edge, pulping their food for easier digestion by cutting through it like scissors.”
Just a few weeks ago, Makovicky was co-author of a paper in Nature describing a different new dinosaur, a small, feathered carnivore, found in the same limestone bed as Liaoceratops. Called Sinovenator, it was not much bigger than a chicken. It not only lived at the same time as Liaoceratops, but it also probably hunted and ate the plant eater, he said.
“Sinovenator might have had trouble one-on-one with an adult Liaoceratops,” he said, “but it could have gone after the juveniles easily and ganged up on adults, too. It isn’t the clash of the titans, of T. rex and Triceratops battling it out. This is more like a rooster and a turtle going at it.”
In fact, he said, there is some speculation on whether the horns and frill on Triceratops, Liaoceratops and other ceratopsians were there for armor and as defensive weaponry, or if it was more ornamental, to attract mates.
For a long time, scientists thought the horns and frill supported large jaw muscles for the big-headed animals. That appears to be true for Liaoceratops, Makovicky said, but there’s not much evidence that those anatomical features served the same purpose for Triceratops.
“Current thinking with Triceratops,” he said, “is that its horns and frill were there not so much for defense against predators, but as sexual ornamentation to attract mates in courtship.
“You see the same thing with various antelope species in Africa, whose shapes and sizes of horns vary a great deal. But they are there as easily seen visual structures, used not for defense but to attract mates.”
Several other feathered dinosaur species also have been found at the Chinese site, where the limestone is so fine-grained that it picked up and preserved feather impressions. Almost all of the species found there have been small, primitive versions of dinosaur lines that evolved into much larger animals.
“It is very rare to come across small dinosaurs,” said Makovicky, “because small bones don’t survive fossilization nearly as well as large bones do. That’s what makes this fossil bed so unusual and valuable.”
Since the original discovery of the two Liaoceratops skulls and partial skeletons, scientists have found more complete skeletal remains of Liaoceratop torsos and legs. Those fossils will be prepared at the Field Museum so that they can be combined with casts of the skulls.
“By the end of the year,” said Makovicky, “we hope to know what the whole critter looks like.”