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A New Pygmy Tyrannosaur Is Discovered to Be T. Rex’s Cousin from North

Scientists found a 70 million-year-old fossil in the Late Cretaceous sediments of Alaska and it was identified to be a new small tyrannosaur, according to a paper published in the journal PLOS ONE on March 12, 2014.

Tyrannosaurs is the lineage of carnivorous theropod (“beast feet”) dinosaurs including the famous T. rex, however, most of our knowledge about this group is from fossils from low- to mid-latitudes of North America and Asia. The partial skull roof, maxilla and jaw recovered from Prince Creek Formation in Northern Alaska was originally believed to belong to another species.

Animated model of Nanuqsaurus hoglundi. *Image source: Nature.


After comparing the fossil to known tyrannosaurine species, the researchers confirmed that the cranial bones belonged to a new tyrannosaurine species, Nanuqsaurus hoglundi, which was closely related to two other tyrannosaurides, Tyrannosaurus and Tarbosaurus. The scientists estimated that the new dinosaur was relatively small and its adult skull length was estimated to be 25 inches, while T. rex had a 60-inch-long skull. The new tyrannosaur inhabited in a seasonally extreme, high-latitude continental environment on the northernmost edge of Cretaceous North America.


An image showing the relative size of Nanuqsaurus hoglundi (A); Tyrannosaurus rex (B,C); Daspletosaurus torosus (D); Albertosaurus sarcophagus (E); Troodon formosus (F), lower latitude individual based on multiple sources and size estimates; Troodon sp. (G), North Slope individual based on extrapolation from measurements of multiple dental samples. The scale bar in this image is 1 m.  *Image source: ScienceDaily.


The researchers note that the smaller body size of the new tyrannosaur, compared to most tyrannosaurids from lower latitudes, might reflect an adaptation process to variability in resources in the arctic seasons. The further diversification of the species can be based on the tyrannosaurs’ partial isolation in the north by land barriers like the east-west running Brooks Range. By far, only fragments of N. hoglundi are discovered, but the researchers are confident to provide support for its place among derived tyrannosaurines according to the morphological data. The new findings may offer new insights into the adaptability and evolution of tyrannosaurs in the Arctic, a different environment.

  “This ‘pygmy tyrannosaur’ is so cool because it gives us cues about what the environment was like in ancient Arctic,” said Fiorillo, co-author of the research. “More excitingly, the discovery also telss us about the biological richness of the ancient Arctic during a time when the Earth was warmer than today.”

Source: ScienceDaily