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Ceratopsids, the horned dinosaurs that roamed western North America as the reign of dinosaurs approached its sudden end, had the largest heads of any land animal that ever lived, although their brains were the size of baseballs.
A new species unveiled Friday by University of Utah paleontologists grabbed another superlative: longest horns of any dinosaur. Coahuilaceratops magnacuerna , among 10 new species identified in a book published next month by Indiana University Press, sprouted four-foot horns over each eye.
Coahuilaceratops, named for the Mexican state where the specimen was recovered by Utah teams in 2002 and 2003, inhabited the southern tip of what was an island continent 72 million years ago, said Mark Loewen, of the Utah Museum of Natural History, lead author of the chapter. This plant-eating creature was 22 feet long and weighed four to five tons. Like other ceratopsids, it had a ridged skull plate, called the frill, sweeping behind its head and a parrot-beaked mouth.
The new book, New Perspectives on Horned Dinosaurs , arose from a 2007 symposium at Alberta's Royal Tyrrell Museum where about 40 scientists gathered to compare notes. The book describes two other new species co-discovered by Utah's state paleontologist James Kirkland, based on specimens recovered on the Colorado Plateau. And U. paleontologists will soon name three more new species based on specimens pulled from the 75-million-year-old Kaiparowits Formation on the Grand Staircase-Escalante National Monument.
Ceratopsids were largely confined to western North America in the Late Cretaceous era, 90 to 65 million years ago. During this period of high global temperatures, this region was isolated by an inland seaway that cut North America in two. In recent years, numerous ceratopsid fossils, representing about 30 species with many more on the way, have been recovered along what was the east coast of this island landmass -- known as Laramidia -- from present-day Alberta, through Montana, Utah, New Mexico to Coahuila.
"We have doubled the known species since 2000. That's a ridiculous rate of discovery," said Scott Sampson, a research curator at the museum and co-author on the coahuilaceratops study. With backing from the National Geographic Society and Mexican partners, Utah scientists are exploring Coahuila's untapped paleontological resources. Coahuilaceratops is only the fourth dinosaur species named from specimens recovered in Mexico.
Paleontologist Claudio de Leon discovered this specimen in 2001 west of the Coahuila capital, Saltillo, where the bones will be housed at the Museo Del Desierto.
"A reason we went to Mexico was to see if there are horned dinosaurs there," Loewen said. "Saltillo is the furthest south on Laramidia. It's the best information we have on the southern end of this continent."
Ceratopsids were generally as large as rhinos and elephants and probably congregated in large herds, foraging in coastal plains that resembled today's humid, lush Louisiana bayou. In Montana and Alberta their fossils often are found in boneyards, believed to have amassed following cataclysmic storms that killed thousands of animals.
"These guys were super successful, they were major players in the ecosystem," said Loewen at a museum event Friday where he displayed a reconstruction of coahuilaceratops' six-foot-long noggin. Scientists recovered only fragments of the frill, jaw, nose and horns, as well as legs and vertebrae, but they were able to create an accurate rendering of a complete skull based on knowledge of other ceratopsids.
"It is completely different from other dinosaurs that lived at the same time. This gives a new picture of the evolution of horned dinosaurs," Loewen said. "They are evolving really fast. Part of that is tied to the fact that they have these horns and ornamented frills. Like deer, this gives them all these signalling structures on the top of their head. Sexual selection is probably selecting them out based on changes in the appearance of the skull."
Scientists once assumed ceratopsids used their bony head gear to ward off large predators, but now they suspect the horns and frills evolved to attract mates, similar to what we see with birds' plumage and antlers on some ungulates.
"Many had horns that were curved downward like can openers and the frills tapered to a width of a millimeter," said Sampson, also known as "Dr. Scott" as host of the PBS show "Dinosaur Train." "These things would make lousy weapons against large predators. They may have been used to increase the appearance of body size."
The scientists suspect ceratopsids' size kept predators at bay. With 10,000 pounds pushing a massive skull, ceratopsids were hardly an appealing target, Loewen said.
Ceratopsids, or horned dinosaurs such as the famous triceratops, evolved in North America in the Late Cretaceous as the reign of dinosaurs was approaching its sudden end 65 million years ago. A new book unveils at least 10 new species, including three identified by Utah scientists.
Coahuilaceratops magnacuerna » described from a specimen recovered in Mexico, was unveiled at the Utah Museum of Natural History on Friday. It sported four-foot horns over each eye and weighed up to five tons.
Diabloceratops eatoni » described from another specimen discovered in Wahweap Formation in the Grand Staircase-Escalante National Monument, was named for Weber State University geosciences professor Jeff Eaton.
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