Coahuilaceratops magnacuerna – The First Horned Dinosaur from Mexico

No sooner do we write an article about the discovery of a new genus of Ceratopsian (horned dinosaur) from the western United States (Medusaceratops lokii), then the University of Utah, publishes a press release about a new genus of horned dinosaur, the first to be discovered in Mexico.

To read more about Medusaceratops lokii: Mystery Horned Dinosaur from Montana

Unlike M. lokii, there is no doubting from the fossil remains that this particular Ceratopsian is a Chasmosaurine, the huge brow horns are a dead give away, and although the scientists admit they have yet to find an entire horn they estimate that the brow horns on C. magnacuerna are some of the biggest known in the fossil record.

This discovery has given scientists fresh insights into the ancient history of western North America, according to a research team led by palaeontologists from the Utah Museum of Natural History at the University of Utah.

“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.”

Commented Mark Loewen, a palaeontologist with the museum and lead author of the study.

The 72-million-year-old rhino-sized creature – Coahuilaceratops magnacuerna – would have weighed perhaps as much as 4 tonnes.  The fossils date from the (Maastrichtian faunal stage of the Late Cretaceous).   The name Coahuilaceratops magnacuerna (pronounced Koh-WHE-lah-SARA-tops mag-NAH-KWER-na), refers to the Mexican state of Coahuila where it was found, and to the Greek word “ceratops” meaning “horned face.”  The second part of the name, or the specific name, magnacuerna, is a combination of Latin and Spanish meaning “great horn,” in reference to the huge horns above the eyes of this dinosaur (the brow horns).

An Illustration of Coahuilaceratops magnacuerna

Picture Credit: Lukas Panzarin

The illustration above shows an artist’s interpretation of the Ceratopsian skull material.  The huge and strongly re-curved brow horns are depicted.

The study, partially funded by the National Geographic Society, was conducted by Mark Loewen, Scott Sampson, Eric Lund and Mike Getty, palaeontologists at the Utah Museum of Natural History.  Also involved were Andrew Farke of the Raymond M. Alf Museum in Claremont, California.; Martha Aguillón-Martínez, Claudio de Leon and Rubén Rodríguez-de la Rosa from the Museum of the Desert in Saltillo, Mexico; and David Eberth of the Royal Tyrrell Museum of Palaeontology in Alberta, Canada.

The new species is to be announced in the book “New Perspectives on Horned Dinosaurs” to be released next week by Indiana University Press.  The lead author for this publication is Dr. Michael J. Ryan and the book will contain more information on the new Montana Ceratopsian M. lokii.

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.  This sea is known as the Western Interior Seaway.

The Fossil skull of this Dinosaur

Coahuilaceratops Illustration

Picture Credit: Utah Museum of Natural History, the University of Utah

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.

Scott Sampson commented:

“As the southernmost dinosaurs on Laramidia, Mexican dinosaurs will be a critical element in unravelling 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 (ruptured oil pipelines not permitting).  Many dinosaur bones in the area are covered with fossilised snails and marine clams, indicating that the dinosaurs inhabited environments adjacent to the seashore.

The Fossil Material Superimposed on a Line Drawing of the Skull

Fearsome Ceratopsian

Picture Credit: Utah Museum of Natural History, the University of Utah

The neck crest is assumed to be fenestrated (exhibiting holes in the bone, that in life would have been covered by skin).  A pair of fenestra are believed to be present, these would have helped lighten the neck crest and the skin patches could have been flushed with blood to make vivid display patterns, perhaps a part of Chasmosaurine courtship.

The rocks in which Coahuilaceratops was found also contain large fossil deposits of jumbled duck-bill dinosaur skeletons.  These sites appear to represent mass death events, perhaps associated with storms such as hurricanes that occur in the region today.

Scott Sampson went on to add:

“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.”

Until recent years, there have been few large-scale palaeontological projects in Mexico focused on the Mesozoic Era.  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, which de Leon 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 by skilled volunteer preparator Jerry Golden.

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 7 metres long as an adult, more than 2 metres high at the shoulder and hips, with a 1.8 metre long skull, it would have weighed more than an adult male Indian elephant.

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 more than one metre in length.

Although such horns are common features of Ceratopsian dinosaurs, those of Coahuilaceratops appear to be the largest known for the group, exceeding the size of eye horns even in Triceratops horridus.  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, although they would have acted as a substantial deterrent against hungry Tyrannosaurs.

Mark Loewen explained that Coahuilaceratops represents the first occurrence of an identifiable species of horned dinosaur in southern Mexico.

He added:

“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 researchers are hoping to find more fossil material so that they can gain more information on these two other types of Ceratopsian.

The latest expedition also recovered remains of two duck-bill 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 (Dromaeosaurs).

Together with an abundance of fossilised bones, researchers discovered the largest assemblage of dinosaur trackways known from Mexico, an extensive area crisscrossed 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.

Commenting on the rich and diverse fossil material Mark Loewen stated:

“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. David Eberth explained that researchers now have two points of comparison to examine not only different dinosaurs, but also different environments and ecologies.

As might be suspected, paleontologists are excited about the future palaeontological potential of this area, they are confident that more dinosaur discoveries will be made.

Don Brinkman, a researcher at the Royal Tyrrell Museum (Drumheller, Alberta) added:

“Dinosaurs from this particular period are important because this is a time that is relatively poorly understood.”

Don is studying non-dinosaur vertebrates found at the site, including turtles, fish, and lizards.

He went onto state:

“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.”

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