Thursday, April 22, 2010

Continent-sized Ecosystems for Dinosaurs

Retracing the tracks of dinosaurs reveals ecosystem the size of a continent

McGill researchers uncover first evidence that warm and moderate climate allowed dinosaurs to expand into one massive homogenous community across North America.

Researchers at McGill University are unlocking the mysteries of the little-known habits of dinosaurs in discovering that the entire western interior of North America was likely once populated by a single community of dinosaurs. According to a statistical analysis of the fossil record, dinosaurs were adept at coping with all sorts of environments, and not as restricted in their geographic ranges as previously thought.

The discovery was made by McGill Professor Hans Larsson and Matthew Vavrek, a PhD student at the University. Using data from the Paleobiology Database (, they found that the difference in species between regions over North America was relatively low - low enough to consider it a single homogeneous fauna. The finding is significant as it confirms that dinosaur ecosystems may have been as large as continents. The paper is to be published in the April 19 issue of the journal Proceedings of the National Academy of Sciences.

The McGill team zeroed in on alpha diversity, the number of species in an immediate area, versus beta diversity, which are the differences in species between two different areas. Their research shows low beta biodiversity among these dinosaurs with values comparable to species living in homogeneous climates today, but on smaller geographic scales. "This is significant because we lack living analogues of a complete terrestrial megafauna living in those kinds of stable climates. The findings give us an insight into what kind of ranges these types of communities may have had," Larsson, a Canada Research Chair in Macroevolution, explained. "We also demonstrate that after more than a century of collecting dinosaurs in North America, we should expect to find about 16 types, on average, in any one region of western North America just before their mass extinction."

The long extinct dinosaurs are not just long dead fossils, but they offer a unique insight into a complex megafauna that responded to their environment. But even though they are extinct, they can tell us about the ecology of the animals we see today. "Despite their appearance, dinosaurs are ecologically very similar to mammals of today," Vavrek said. "They were able to colonize and dominate the landscape over very large distances, and were not nearly as constrained as we might have once thought."

By examining a single time slice, the Maastrichtian stage (71-65 million years ago) and all known specimens of dinosaurs from the Western Interior region of North America, the duo concluded that multiple dinosaur faunal regions did not exist. "Our results show low beta diversity and support a single dinosaur community within the entire Western Interior region. This widespread ecosystem was likely due to the homogenous climate present in this region at the time." said Larsson. "What is exciting about this result is that now we can begin to ask many more questions about how such a large homogeneous community of dinosaurs lived. Did they migrate, or have adequate amounts of gene flow between regional populations, or a mixture of both? How did this widespread dinosaur megafaunal community affect other animals and plants on the regional and continental scale? We're just beginning to scratch the surface of dinosaur ecology."


See a nice response from Utah Museum of Natural History's Scott Sampson.

Image: Dinosaur stamp, art by James Gurney

Tuesday, April 20, 2010

Another Bonehead Found

New Bony-Skulled Dinosaur Species Discovered in Texas

New Haven, Conn. — Paleontologists have discovered a new species of dinosaur with a softball-sized lump of solid bone on top of its skull, according to a paper published in the April issue of the journal Cretaceous Research.

The species was a plant-eating dinosaur about as big as a medium-sized dog that lived 70 to 80 million years ago, said Nicholas Longrich of Yale University, lead author of the paper. The team discovered two skull fragments in Big Bend National Park in southwest Texas in 2008. They compared them to dozens of fossils from related species found in Canada and Montana before confirming that the fossils represented a new genus of pachycephalosaur, a group of bipedal, thick-skulled dinosaurs.

The researchers named the new species Texacephale langstoni. (“Texacephale” means “Texas head” and “langstoni” is in honor of Wann Langston, a fellow paleontologist.) The new species is one of about a dozen known to have solid lumps of bone on top of their skulls, which Longrich speculates was probably used to ram one another head-on in a manner similar to modern-day musk oxen and cape buffalo.

The discovery of the new species lends further weight to the idea, which has gained popularity in recent years, that dinosaurs found in Canada and the northern United States were distinct from their southern neighbors.

“Instead of roaming across the North American continent, we see pockets of different dinosaurs that are pretty isolated from one another,” Longrich said. “Every time we get good fossils from Texas, they end up looking very different from those to the north.”

Because fossils from the Big Bend region are rare and tend to be poorly preserved, scientists do not have a complete picture of the different species that once inhabited the area, Longrich said.

But the team may have uncovered an important piece of the puzzle with their discovery. They found that this particular group of dinosaurs, which was previously thought to have originated in Asia, likely evolved in North America.

Longrich expects more related species to be discovered in the future as fossils from the Texas site and elsewhere continue to be examined.

“I think we underestimate how many different species there were,” he says.

Other authors of the paper include Julia Sankey (California State University, Stanislaus), who led the fieldwork, and Darren Tanke (Royal Tyrrell Museum), who discovered the more complete specimen on which the naming of the new species was based.

FOUND IN: Science & Engineering Yale Bulletin

Photo: Dracorex hogwartsia, a pachycephalosaur