PHYSorg.com—A new horned dinosaur, Medusaceratops lokii, approximately 20 feet long and weighing more than 2 tons, has been discovered in Montana. The newly identified plant eating dinosaur lived nearly 78 million years ago during the Late Cretaceous period. Its identification marks the discovery of a new genus of horned dinosaur. And another new species of horned dinosaur unearthed in Mexico has larger horns that any other species—up to 4 feet long—and has given scientists fresh insights into the ancient history of western North America, according to a research team led by paleontologists from the Utah Museum of Natural History at the University of Utah.
Montana
Medusaceratops belongs to the Chasmosaurinae subfamily of the horned dinosaur family Ceratopsidae. The other subfamily is Centrosaurinae. The specimen is the first Campanian aged chasmosaurine ceratopsid found in Montana. It is also the oldest known Chasmosaurine ceratopsid.
The new dinosaur was discovered in a bonebed on private land located along the Milk River in North Central Montana. Fossilized bones from the site were acquired by Canada Fossil, Inc, of Calgary, Alberta, in the mid-1990s. The company consulted with Ryan and his colleagues to identify material from the site. At first, the scientists could not make a positive identification.
Medusaceratops had giant brow bones more than 3 feet long over each eye, and a large, shield-like frill off the back of its skull adorned with large curling hooks. Medusaceratops lokii means “Loki’s horned-faced Medusa”, referring to the thickened, fossilized, snake-like hooks on the side of the frill. It was named after Loki, the Norse god of mischief, because the new dinosaur initially caused scientists some confusion.
Ryan said:
At first we couldn’t figure out what we had. Some of the material looked as if it came from a form related to Centrosaurus, a centrosaurine noted for having short brow horns. The rest of the pieces had giant brow horns similar to Triceratops, a chasmosaurine. That’s one of the problems with bonebed seven, though you can collect a large amount of material, much of it is broken and all of it is disarticulated, so the story is rarely clear cut.
Eventually Ryan found a complete articulated skull of a centrosaur with long brow horns in southern Alberta of what appeared to be the new animal from Montana, and named it Albertaceratops in 2007. At that time, he assumed he was looking at a stray that had literally crossed the international border millions of years ago. After reexamining the Montanan material, Ryan realized that at least some of the material in the Montana bonebed was not Albertaceratops. Some of the elements were much larger than any other horned dinosaur from the same time period, including Albertaceratops. And even though Albertaceratops and Medusaceratops are superficially similar, the shape and number of the hooks and ornaments along the edge of the frill actually puts them in separate horned dinosaur groups, with Medusaceratops being a chasmosaur. Co-author, Anthony Russell, professor of biological sciences at the University of Calgary in Alberta, said:
Although the ornamentation on the frill is pretty spectacular, it probably was not used for defense against predators. Rather it was more likely prehistoric “bling” used to attract a mate.
Medusaceratops is the oldest member of the Chasmosaurinae in North America and shows that the group, like its most famous member, Triceratops, had long brow horns and were fairly large when they first evolved. But later chasmosaurs that are just a bit younger than Medusaceratops tend to have much shorter horns and have much smaller, lighter bodies. Ryan said
Here we have something almost the size of Triceratops, but 10 million years before it lived. T rex was not around yet, so what was Medusaceratops squaring off against? That’s one of the things we’re now looking for in Alberta.
Mexico
Meanwhile, in Mexico, a new horned dinosaur has given scientists fresh insights into the ancient history of western North America. Mark Loewen, a paleontologist with the Utah Museum of Natural History and lead author of the study, said:
We know very little about the dinosaurs of Mexico, and this find increases immeasurably our knowledge of the dinosaurs living in Mexico during the Late Cretaceous.
The 72-million year old rhino sized creature, Coahuilaceratops magnacuerna, was a four to five ton plant eater belonging to a group called horned dinosaurs, or ceratopsids, from the Greek word ceratops meaning “horned face”.
The study was partially funded by the National Geographic Society.
A Different World
For most of the Late Cretaceous Period, from 97 million to 65 million years ago, high global sea levels resulted in flooding of the central, low lying portion of North America. As a result, a warm, shallow sea extended from the Gulf of Mexico to the Arctic Ocean, splitting the continent into eastern and western landmasses.
Dinosaurs living on the narrow, peninsula-like western landmass—known as Laramidia—occupied only a narrow belt of plains that were sandwiched between the seaway to the east and rising mountains to the west. Central America had not formed at the time, which made Mexico the southern tip of this island continent.
In many ways, the Late Cretaceous is the best understood time during the Age of Dinosaurs, thanks in large part to more than 120 years of dinosaur hunting in Canada, Montana, New Mexico and the Dakotas. Recent work has revealed new dinosaurs living at the same time in Utah, New Mexico and Texas, yet the dinosaurs from Mexico have remained virtually unknown. One of the team who made the discovery said:
As the southernmost dinosaurs on Laramidia, we are confident that Mexican dinosaurs will be a critical element in unraveling the ancient mystery of this island continent.
Loewen described the arid, desert terrain where the dinosaur was recovered as nothing like Mexico during the Late Cretaceous. About 72 million years ago, the region was a humid estuary with lush vegetation, an area where salt water from the ocean mixed with fresh water from rivers, much like the modern Gulf Coast of the southeastern United States. Many dinosaur bones in the area are covered with fossilized snails and marine clams, indicating that the dinosaurs inhabited environments adjacent to the seashore.
The rocks in which Coahuilaceratops was found also contain large fossil deposits of jumbled duck billed dinosaur skeletons. These sites appear to represent mass death events, perhaps associated with storms such as hurricanes that occur in the region today. One of the scientists said:
Sitting near the southern tip of Laramidia, this region may have been hammered by monstrous storms. If so, such periodic cataclysms likely devastated miles of coastline, killing off large numbers of dinosaurs.
Recovering a Giant Horned Head
Until recent years, there have been few large scale paleontological projects in Mexico focused on the Mesozoic Era, from 253 million to 65 million years ago, also known as the Age of Dinosaurs. Indeed Coahuilaceratops is among the first dinosaurs from Mexico to be named.
Coahuilaceratops comes from a rock unit known as the Cerro del Pueblo Formation, which dates to between 71.5 million and 72.5 million years ago. The skeletons, discovered in 2001 near the town of Porvenir de Jalpa, approximately 40 miles west of Saltillo, were excavated in 2003. The fossils then were prepared at the Utah Museum of Natural History, requiring two years of meticulous work.
Based on the bone development of the skull and skeleton, the scientists believe that this animal was an adult at the time of death. Remains of a juvenile animal of the same species were also found at the site. Coahuilaceratops was about 22 feet long as an adult, 6 feet to 7 feet tall at the shoulder and hips, with a 6 feet long skull, and likely weighed about four to five tons. Being one of the largest herbivores in its ecosystem, adult Coahuilaceratops probably did not have to worry about large tyrannosaur predators.
By far the most obvious characteristic of Coahuilaceratops is its massive pair of horns, one above each eye. While the researchers lack a complete horn, they estimate from fossils they excavated that the horns were 3 feet to 4 feet long, Loewen said.
Although such horns are common features of ceratopsid dinosaurs, those of Coahuilaceratops appear to be the largest known for the group, exceeding the size of eye horns even in Triceratops. Scientists are uncertain of the massive eye horns’ purpose, but the most widely accepted idea is that they were related to reproductive success, functioning to attract mates and fight with rivals of the same species.
Coahuilaceratops is the first identifiable species of horned dinosaur found in southern Mexico. The horned dinosaurs are an extraordinary example of vertebrate evolution. They evolved and diversified on Laramidia along a thin strip of land that stretched from Alaska to Mexico. Finding this horned dinosaur so far south in Mexico offers us a different picture of what the ancestors of Triceratops were like.
In addition to Coahuilaceratops, the research team found remains of two other horned dinosaurs, which are less well understood. The latest expedition also recovered remains of two duck billed dinosaurs, as well as the remains of carnivores, including large tyrannosaurs (smaller, older relatives of T rex) and more diminutive Velociraptor-like predators armed with sickle claws on their feet.
Together with an abundance of fossilized bones, researchers discovered the largest assemblage of dinosaur trackways known from Mexico, an extensive area criss-crossed with the tracks of different kinds of dinosaurs. In all, the emerging picture shows a diverse group of dinosaurian herbivores and carnivores, perhaps representing a previously unknown assemblage of species. Loewen said:
Rather than focusing only on individual varieties of dinosaurs, we are attempting to reveal what life was like in Mexico 72 million years ago, and understand how the unique ecosystem of Mexico relates to ecosystems to the north at the time.
Few North American dinosaurs from this time period are known outside of the Drumheller region of Alberta. Eberth explained that researchers now have two points of comparison to examine not only different dinosaurs, but also different environments and ecologies. Don Brinkman, a researcher at the Royal Tyrrell Museum. He is studying non-dinosaur vertebrates found at the site, including turtles, fish, and lizards, added:
Dinosaurs from this particular period are important because this is a time that is relatively poorly understood. The locality in Mexico goes a long way to filling in a gap in our knowledge of the record of changes in dinosaur assemblages throughout the Late Cretaceous.
