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Fossil of Dog-Size Horned Dinosaur Unearthed in China

John Roach
for National Geographic News
Updated March 22, 2002
 
Researchers have announced their discovery of a very distant cousin to
Triceratops, the well-known three-horned dinosaur with a massive
bony protrusion behind its skull.

The discovery is an important
piece in the evolutionary puzzle of the horned dinosaurs. Although they
are considered one of the most diverse groups of dinosaurs, little is
known about their early evolution.

Named Liaoceratops yanzigouensis, the newest find hails from the fossil-rich Yixian Formation in northeast China. Its discoverers say the dog-size creature is the oldest, smallest, and most primitive of the neoceratopsians, one of the two main lineages of horned dinosaurs.

"Liaoceratops gives us a great window on the early evolution of the group and tells us that Triceratops and its relatives evolved from very small Asian ceratopsians," said Peter Makovicky, a dinosaur curator at the Field Museum in Chicago and the co-discoverer of Liaoceratops.



The paleontologists, who reported the Liaoceratops discovery in the March 21 issue of Nature, date the fossils to about 130 million years ago. This indicates that ceratopsians branched into the two main lineages of neoceratopsians and psittacosaurids (parrot-beaked dinosaurs) much earlier than previously believed.

Of Horns and Frills

Triceratops was the largest of the ceratopsians—some 30 feet (nine meters) long and weighing an estimated 14,000 pounds (6,350 kilograms). Three prominent horns and a large frill at the back of the skull are the distinguishing characteristics of Triceratops.

Scientists do not know why ceratopsians of the Late Cretaceous (75 to 65 million years ago) evolved large horns and frills. Various people have suggested that these prominent features were used to attract mates, much like the horns of antelope; for defense; or to support large jaw muscles.

The discovery of Liaoceratops doesn't explain the reason for these distinguishing characteristics, but does indicate that all of the various evolutionary theories could be correct.

Liaoceratops has two small horns—one below each eye that appear to be for display, said Makovicky. A small frill at the back of its skull, however, is marked by clear scars for the attachment of chewing muscles, he added.

"It appears that the expanded and ornate frills and many of the horns of large, advanced ceratopsians evolved later in the history of this group as the animals became larger, although Liaoceratops shows the beginnings of these features," he said.

The paleontologists do not believe that Liaoceratops used its horns and frill as a defense mechanism. "It was probably preyed on by theropod [meat-eating] dinosaurs and perhaps crocodiles," said Mark Norell, a paleontologist at the American Museum of Natural History in New York and co-author of the study.

Stubby horns and a small frill would have been of little use warding off such creatures. Rather, Liaoceratops likely relied on concealment and flight in the lush forests of the Yixian region for protection.

Complex Evolution

The discovery of Liaoceratops adds a few more pieces to the already complex puzzle of ceratopsian evolution.

"On one hand, the discovery of Liaoceratops fills the morphological [form and structure of the animal] gap between the primitive psittacosaurid and advanced neoceratops," said Xing Xu of the Institute of Vertebrate Paleontology & Paleoanthropology at the Chinese Academy of Sciences in Beijing and lead author of the study.

"On the other hand, it introduced more homoplasies [body features acquired as a result of parallel evolution or convergence of species] and thus makes the early evolution of ceratopsian dinosaurs more complicated."

Examination of the Liaoceratopsian fossils (one adult, one juvenile) indicates that while Liaoceratops shared many characteristics with the neoceratopsians, it also retains a number of characters of the more primitive psittacosaurids.

Xu said this suggests that the characteristics of horned dinosaurs evolved independently of each other and, in some cases, more gradually than was previously believed.

"Basically, dinosaurian evolution is a complicated process and our knowledge about dinosaurs appears to be far from enough to completely understand this unusual group of animals," he said.

Xu's research was supported by the National Geographic Society's Committee for Research and Exploration.

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Additional dinosaur resources from National Geographic:
Paul Sereno: National Geographic Explorer-in-Residence and Dinosaur Hunter
Dinorama
Wanted: Albertosaurus
Dinosaur Eggs
Destinations: Dinosaur National Monument
 

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