Two new horned dinosaurs, one from Utah and the other from Montana, each sported distinctive facial horns and spiked neck shields, according to two separate papers published in the journal PLOS ONE.
The discoveries increase the known diversity of ceratopsians, which were plant-eating horned dinos that roamed North America and Asia during the final stages of the age of dinosaurs.
One of the new dinosaurs, Machairoceratops cronusi, lived 77 million years ago at what is now called the Grand Staircase-Escalante National Monument of southern Utah. This was during a time when North America was subdivided by a sea into western (Laramidia) and eastern (Appalachia) landmasses.
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Machairoceratops measured about 26 feet long and weighed as much as 4409 pounds. Lead author and Ohio University graduate student Eric Lund told Discovery News that the dinosaur possessed "two large, forward curving spikes off of the back of the neck shield, each of which is marked by a peculiar groove extending from the base of the spike to the tip."
The neck shield, also called a "frill" since the bony mass has a decorative nature, was "probably utilized during within species interactions including sexual display and mate competition," Lund said. He added, "The spikes probably also functioned in a between species aspect for species recognition allowing (dinosaurs of the same species) to recognize one another. The function and purpose of the unique groove marking the posterior margin of the spikes is totally unknown as this is a character not observed in any other horned dinosaur."
The discovery of Machairoceratops strengthens the idea that ceratopsians occupied two distinct regions that were separated within Laramidia, and suggests that different evolutionary pressures acted upon the groups during the late Cretaceous. Although many fossils of this dino group have been discovered in what were once northern regions of Laramidia (Alaska, Alberta, Montana, and Saskatchewan), relatively few have been recovered from the southern portion (Utah, Colorado, New Mexico, Texas, and Mexico) of the ancient continent.
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"An effort like this underscores both the necessity and excitement of basic, exploratory science in order to better understand the history of the world around us," noted study co-author Patrick O'Connor, who is a professor of anatomical sciences at the Heritage College of Osteopathic Medicine. "Even in a place like western North America, where intense work has been conducted over the past 150 years, we are still finding species new to science," he added.
The other new horned dinosaur with neck spikes was found in Montana a decade ago, but was only recently studied and identified. It has been named Spiclypeus shipporum, meaning "spiked shield." The name "shipporum" honors the Shipp family on whose land the fossil was found near Winifred, Montana, by retired nuclear physicist Bill Shipp, who is now a fossil enthusiast.
The dino has a nickname too - Judith - after the Judith River geological formation where it was found.
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What sets Judith apart from other horned dinosaurs is the orientation of the horns over its eyes, which stuck out sideways from the skull, and a unique arrangement of bony "spikes" that emanated from the margin of its neck shield. Some of these spikes curled forward, while others projected outward, giving the shield a true frilly look.
"This is a spectacular new addition to the family of horned dinosaurs that roamed western North America between 85 and 66 million years ago," explained co-author Jordan Mallon of the Canadian Museum of Nature. "It provides new evidence of dinosaur diversity during the Late Cretaceous period from an area that is likely to yield even more discoveries."