Nanuqsaurus hoglundi
March 13, 2014

Petite Cousin Of The Tyrannosaurs Rex Detailed In New Report

Brett Smith for - Your Universe Online

The reexamination of a dinosaur skull found in Alaska has revealed that it may have belonged to a “smaller cousin” of Tyrannosaurs Rex – not a completely distinct species as originally believed.

According to a report on the examination published on Wednesday in the journal PLoS ONE, the skull belonged to a lineage of theropods, or “beast feet,” dinosaurs that includes T. Rex.

With most T. Rex fossils coming from temperate and sub-tropical parts of North America, this smaller carnivorous dinosaur could represent the lineage’s adaptation to more Arctic climes. The dinosaur was dubbed Nanuqsaurus hoglundi, derived from the native Inupiaq language, which means “polar bear lizard.”

"The 'pygmy tyrannosaur' alone is really cool because it tells us something about what the environment was like in the ancient Arctic," said study author Anthony Fiorillo, from the Perot Museum of Nature and Science in Dallas. "But what makes this discovery even more exciting is that Nanuqsaurus hoglundi also tells us about the biological richness of the ancient polar world during a time when the Earth was very warm compared to today."

While the North Slope region of Alaska where the fossil was found was much warmer during the Cretaceous period than it is now – similar to the climate of Oregon or Washington State – it was still much colder than the tropical environments we typically associate with dinosaurs. Also during the Cretaceous, this part of Alaska was even further north than it is now, meaning seasonal daylight patterns were even more dramatic than they are today.

In their study, the scientists learned that N. hoglundi is closely linked to two other tyrannosaurides, Tarbosaurus and Tyrannosaurus. Thought to have an adult skull length of about 25 inches, compared to 60 inches for T. rex, the authors said the relatively smaller body size of N. hoglundi may reflect an adjustment to variability in resources that occurred in this region of Alaska at the time. The dinosaurs' further diversification may have resulted from partial isolation in the north due to topographical barriers.

“The North Slope was, effectively, an isolated area,” Fiorillo told the Alaska Dispatch.

He added that fossil fragments recovered by the team were from a type of jaw configuration only seen in mature tyrannosaurs.

“That’s what told us we had a fully mature animal,” Fiorillo said.

The new revelation supports the notion that dinosaurs could exist at higher latitudes and were not completely cold-blooded. Some have even speculated that carnivorous dinosaurs had feathers for keeping warm.

“That would suggest the animals would have a metabolism rate that was more like a warm-blooded metabolism than a cold-blooded,” Fiorillo noted.

With limited food available during the winter months, scientists still aren’t sure how these animals would have survived during the leanest times of the year.

“We would love to know,” Fiorillo said, but added that the “best we can do” for now is to make comparisons with what animals do today – which is accumulate fat stores during the warmer months and slow down their metabolism in winter.