by: a thin, rostrally forked, median spur of the fused parietals on the dorsal skull roof that overlaps and separates the frontals within the sagittal crest, frontals with a long, rostrally pointed process separating the prefrontal and lacrimal facets and that the first two dentary teeth are much smaller than the dentary teeth behind them. Classification Phylogenetic analysis of the Tyrannosauridae finds Nanuqsaurus to be a close relative of Daspletosaurus and Tyrannosaurus within Tyrannosaurinae. Below is a cladogram illustrating the relationships of the Tyrannosauridae: Paleobiology According to paleontologists, about 70 million years ago northern Alaska was a part of an ancient subcontinent called Laramidia and experienced cold weather and extreme changes in the amount of daylight during the year, with seasons in which food was not readily available. Prey availability likely would have increased substantially during the summer, but then declined in the dark winter, leaving predators with little to eat. Fiorillo and Tykoski stated that this lack of food might explain Nanuqsaurus'''s unusually small size for an advanced tyrannosaur, as a large animal cannot survive on scarce resources. Nanuqsaurus may have evolved a smaller size because of the decrease in year-round food supply, caused by the colder temperatures. In contrast, it was also found that the normal length of Troodon was 50% larger in Alaska compared to more southerly areas, possibly because a larger eye size allowed it to hunt more effectively in low-light conditions. However, Druckenmiller et al. state that the holotype of Nanuqsaurus represents a younger individual, based on the physical evidence of undescribed teeth and postcranial remains or larger individuals closer in size to other North American tyrannosaurids like Albertosaurus sarcophagus which is in length. This contradicts the original interpretation of Nanuqsaurus being a dwarf tyrannosaurid being 5-6 meters in length. Paleoecology The holotype specimen assigned to Nanuqsaurus comes from the Maastrichtian age Prince Creek Formation. At an age of 71–68 million years ago, the Kikak-Tegoseak Quarry region Prince Creek Formation dates to the early Late Maastrichtian. An average age found in dating rocks from the formation is 69.1 ± 0.3 million years ago, so it is likely that Nanuqsaurus is from around that age. The formation is along the Colville River on the North Slope Borough, and is made up of alluvial sediments. It is one of a few dinosaurs to live at very high-latitude areas.Nanuqsaurus lived alongside many other dinosaurs in the Prince Creek