Long before the Napoleon Complex became a common way to refer to those of us who are small but strong, the Nanuqsaurus hoglundi sauntered Alaska’s North Slope, unaware history would identify her as the smallest of the great tyrannosaurids. During the Late Maastrichtian, Nanuqsaurus, closely related to the infamous T. rex, hunted in an environment with drastic seasonal shifts and only six months of light. Scientists believe its body size may have been adaptive for resource limitations in a high latitude continent.

In a study recently published in PLOS ONE, three separate pieces of a skull were found in close proximity to one another, including part of the right maxilla, a section of skull roof and braincase, and the rostral part of the left dentary. These fragments, from the Prince Creek Formation on Alaska’s North Slope, provided a new perspective into the adaptability of tyrannosaurids, along with their diversity and distribution.

In 2006, researchers initially uncovered the rocks in which the Nanuqsaurus fossils were imbedded in the Kikak-Tegoseak Quarry in Alaska. At first, they were unclear whether they had found a dinosaur specific to the Arctic or just a northern example of a species from other parts of the world. “Only in the last year or so, after some other tyrannosaur papers came out, we were able to plug these fragments into those analyses — and a little light bulb went on over our heads,” said Ronald Tykoski, paleontologist at the Perot Museum of Nature and Science in Texas. “We said, holy smokes, this thing really is different.”


Fiorillo et. al
This image from the study shows a number of theropods and their relative body sizes. ‘A’ represents Nanuqsaurus hoglundi, while ‘B’ and ‘C’ are both representations of Tyrannosaurus rex.

Nanuqsaurus “sets the standard for what a small adult tyrannosaur looks like,” said Thomas Carr, a paleontologist involved in the research from Carthage College in Wisconsin. The research team determined the Nanuqsaurus fossils came from a fully grown dinosaur because one jaw section shows a distinctive peg-and-socket pattern that is found only in adults.

“I never thought I’d see a dwarf tyrannosaur come to light,” said Carr. From nose tip to tail tip, if they would stand still (and not bite), T. rex would measure twelve meters, while Nanuqsaurus, only seven.

Today the Nanuqsaurus, named after the Inuit word for polar bear (“nanuq”), can stand tall knowing she provides new insights into adaptability and evolution in a prehistoric Arctic.

Source:
Fiorillo A., Tykoski R., (2014) A Diminutive New Tyrannosaur from the Top of the World. PLOS ONE 9(3): e91287. doi:10.1371/journal.pone.0091287

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Published On: April 17, 2014

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