Scientists have identified a new species of a 77-million-years-old horned dinosaurs in the US which sported iconic parrot-like beaks, distinctive facial horns and spiked neck shields.
Although many fossils of this group have been discovered in North America, particularly from the northern portion of the Cretaceous landmass Laramidia (Alaska, Alberta, Montana, and Saskatchewan), relatively few have been recovered from the southern portion (Utah, Colorado, New Mexico, Texas, and Mexico) of this ancient continent.
The new species of centrosaurine, a member of the large-bodied ceratopsians (horned dinosaurs), is named Machairoceratops cronusi.
The researchers from Ohio University and the Natural History Museum of Utah (NHMU) unearthed the characteristic horncores and other skull elements in the Grand Staircase-Escalante National Monument in Utah.
Comparisons with other horned dinosaurs unveiled unique features, indicating the animal was different from other horned dinosaurs - including those from elsewhere in Utah.
"The discovery of Machairoceratops not only increases the known diversity of ceratopsians from southern Laramidia, it also narrows an evolutionary information gap that spans nearly 4 million years between Diabloceratops eatoni from the lower middle Wahweap Formation and Nasutoceratops titusi from the overlying Kaiparowits Formation," said Eric Lund, graduate student at the Ohio University.
Machairoceratops lived about 77 million years ago during the end of the Cretaceous Period, when North America was subdivided by an epicontinental sea (one within a continent) into western (Laramidia) and eastern (Appalachia) landmasses.
Centrosaurine ceratopsids, the group that includes Machairoceratops, were herbivorous dinosaurs known for their iconic, parrot-like beaks, enlarged noses, facial horns, and ornamented frills (neck shields).
Machairoceratops is estimated to have been six to eight metres long and may have weighed as much as one to two tonnes.
The skull of the new species exhibits similarities with the only other centrosaurine (Diabloceratops) yet named from southern Laramidia.
However, the two southern dinosaurs are distinctly different from one another, and, most notably, quite distinct from centrosaurines known from northern Laramidia.
"Machairoceratops is unique in possessing 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 function of which is currently unknown," said Lund.
The discovery of Machairoceratops bolsters the idea that ceratopsians occupied two distinct regions that were latitudinally separated within Laramidia, and suggests that different evolutionary pressures acted upon the groups during the late Cretaceous.
The study was published in the journal PLOS ONE.
