Paleontologists from Perot Museum of Nature and Science in Dallas, Texas, have discovered the fossils of a new diminutive tyrannosaur that lived in what is now Alaska during the late Cretaceous period, about 70 million years ago.
Nanuqsaurus hoglundi. Image credit: Karen Carr.
Large carnivorous dinosaurs known as tyrannosaurs were dominant land predators in Asia and western North America during Cretaceous.
The known diversity of this group has dramatically increased in recent decades with new finds, but overall understanding of their ecology and evolution is based almost entirely on fossils from southern Canada and central Asia.
The partial skull roof, maxilla, and jaw of a previously unknown tyrannosaur were unearthed from the earliest Late Maastrichtian of the Prince Creek Formation on Alaska’s North Slope.
The new dinosaur, scientifically named Nanuqsaurus hoglundi, is a close relative of two famous tyrannosaurs – Tarbosaurus and Tyrannosaurus.
The genus name, Nanuqsaurus, is combination of the Iñupiaq word ‘nanuq’ (polar bear) and the Greek ‘sauros’ (lizard). The specifc name, hoglundi, honors the Texas philanthropist Forrest Hoglund, for his career in earth sciences and his philanthropic efforts in furthering cultural institutions.
According to a study published in the open-access journal PLoS ONE, Nanuqsaurus hoglundi was relatively small with an adult skull about 64 cm long, compared to 1.5 meters for Tyrannosaurus rex.
The tyrannosaur inhabited a seasonally extreme, high-latitude continental environment on the northernmost edge of what is today North America.
Reconstruction of a generalized skull of Nanuqsaurus hoglundi, with preserved elements shown in white, and the fossilized bones. Scale bar is 10 cm. Image credit: Fiorillo AR / Tykoski RS.
The study authors, Dr Anthony Fiorillo and Dr Ronald Tykoski, said the smaller body size of Nanuqsaurus hoglundi compared to most tyrannosaurs may reflect an adaptation to variability in resources in the Arctic. Further diversification may stem from the dinosaurs’ partial isolation in the north by land barriers, such as the east-west running Brooks Range.
“The pygmy tyrannosaur alone is really cool because it tells us something about what the environment was like in the ancient Arctic,” Dr Fiorillo said.
“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.”
Although Nanuqsaurus hoglundi fossils are fragments, Dr Fiorillo and his colleague point to morphological data to provide support for its place among derived tyrannosaurines.
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Fiorillo AR, Tykoski RS. 2014. A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE 9 (3): e91287; doi: 10.1371/journal.pone.0091287
