Nanuqsaurus

Back in the Cretaceous North America was divided into two land masses due to the presence of the Western Interior Seaway,‭ ‬a shallow sea that submerged the central portions of North America all the way from Canada to Mexico.‭ ‬These two land masses were Appalachia in the‭ ‬east,‭ ‬and Laramidia in the‭ ‬west,‭ ‬and with the *Nanuqsaurus* holotype fossils coming from Alaska,‭ ‬we know that this tyrannosaur lived in northern Laramidia.‭ ‬This is considerably further north than many of the more famous and larger North American tyrannosaurs,‭ ‬which has led to a lot of sudden interest about *Nanuqsaurus*.

      Because *Nanuqsaurus* seem to have lived so far north,‭ ‬they would have lived in a much colder environment than that experienced by the Southern tyrannosaurs.‭ ‬This in turn has led to the suggestion that *Nanuqsaurus* may have had at least a covering of insulatory feathers over its body in order to better survive this environment.‭ ‬There is no direct fossil evidence that proves that *Nanuqsaurus* had feathers,‭ ‬but the discovery of *Yutyrannus* in China,‭ ‬and‭ ‬ also interpreted as living in a cool environment,‭ ‬proves that at least some of the larger tyrannosaurs were feathered all over.

      If *Nanuqsaurus* spent most of its time living in the region were the holotype was found and was not merely passing through,‭ ‬then these tyrannosaurs would have experienced a greater seasonal variation that other tyrannosaur genera living further south.‭ ‬This variation could include extended periods of daylight in summer months,‭ ‬and extended periods of darkness in winter months.‭ ‬This may have also brought about a seasonal availability of prey with dinosaurs such as ceratopsians and hadrosaurs moving further‭ ‬north to feed upon fresh plant growth in summer,‭ ‬then migrating further South in winter.

      Because of the incomplete state of preservation for the holotype remains,‭ ‬only a best guess is available for the size estimate of *Nanuqsaurus*.‭ ‬This however does show that if the‭ ‬adult size was about six meters long,‭ ‬then *Nanuqsaurus* would have been relatively small for a tyrannosaur,‭ ‬especially a genera alive in the late Cretaceous.‭ ‬It is possible that the small size of *Nanuqsaurus* may have been a result of living in its environment,‭ ‬especially if prey resources were scarce.‭ ‬Also of interest is that other predatory dinosaurs of the region such as *Troodon* are known to have grown half as big again as their southern relatives.‭ ‬Gigantism is a surprisingly common method that animals adopt to cope with colder climates because the greater mass of their bodies offers more insulation for the internal organs,‭ ‬so the reduction in size for *Nanuqsaurus* again seems to be driven by the availability of food.

      Although the skull of *Nanuqsaurus* is incomplete,‭ ‬is does show that *Nanuqsaurus* would have had a‭ ‬heightened sense of smell,‭ ‬perhaps proportionately even greater than that of *Tyrannosaurus*.‭ ‬This would suggest that smell was an integral part of the *Nanuqsaurus* survival method,‭ ‬but how is likely to further the scavenger debate about tyrannosaurs.‭ ‬A sense of smell could be used to track living animals that otherwise might not have been easy to spot in the polar gloom.‭ ‬In addition this sense of smell may have been used to sniff out carrion,‭ ‬or perhaps even the kills of *Troodon* which had exceptionally good eyesight and so were probably still able to hunt in the dark.‭ ‬Even though small at six meters,‭ *‬Nanuqsaurus* was still much bigger than‭ *‬Troodon* and so may have still been capable of driving them away from their kills.‭ ‬This is pure conjecture however,‭ ‬as a good sense of smell can serve both a predator and a scavenger.‭ ‬There is also a world of difference between opportunistic scavenging,‭ ‬something that most meat eaters do,‭ ‬and obligate scavenging which is when an animal only scavenges.

      The partial remains of *Nanuqsaurus* were first thought to represent remains of either *Gorgosauurs* or *Albertosaurus* until they were finally realised to actually represent a whole new genus of tyrannosaur.‭ ‬Even though‭ *‬Nanuqsaurus* was once thought to represent an albertosaurine tyrannosaur,‭ ‬it is now thought to be a tyrannosaurine,‭ ‬and phylogenetically be close to *Tyrannosaurus*,‭ *‬Tarbosaurus* and *Zhuchengtyrannus*.