MEANING: Polar bear lizard
PERIOD: Late Cretaceous
CONTINENT: North America
Nanuqsaurus is a tyrannosaurid theropod from what is now Alaska. 70 million years ago, Alaska experienced cold weather and extreme changes in daylight during the year, implying that Nanuqsaurus may have been endothermic. Nanuqsaurus was likely similar in size to other North American tyrannosaurids - as much as 9 m in length.
Nanuqsaurus is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.
The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.
On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known goups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene (K–Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K–Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.
Nanuqsaurus is a tyrannosaurid. Tyrannosauridae is a family of theropod dinosaurs known for often being the largest predators in their ecosystems, at the top of the food chain. They lived near the end of the Cretaceous Period in North America and Asia. Tyrannosaurids were bipedal carnivores with massive skulls and large teeth. Their long legs were proportioned for fast movement, but their arms were very small, and only had two functional digits.