Paleontologists have discovered in the formation Prince Creek in Alaska, a fragment of mandible dromaeosaurid, a close relative saurornitholestes, reported in PLoS ONE. Previously, there were only separate the teeth of the members of this group. Given the size of the jaw, the owner at the time of death was very young and likely hatched from eggs near the place where he died. Perhaps the theropods were reproducing in the Arctic circle and lived there year-round.
At the end of the Cretaceous period, about 70 million years ago, Alaska was located further North than now. The climate there was not as severe as it is now (average temperature of the coldest months was about 2-4 degrees Celsius), however warm it is difficult to call (the average temperature of the warmest months is estimated at 10-12 degrees Celsius). However, in the region continue to find many types of dinosaurs and even mammals — the most Northern discovery of metatherian, Unnuakomys hutchisoni, it from there.
It is unclear whether living the Alaskan dinosaurs year-round in one place or migrated like a reindeer. More interestingly, the vast majority of there reptiles were herbivores, but carnivorous theropod almost did not find. They are only a few teeth attributed to troodon and nanaksar (the latter is still considered the most Northern tyrannosaurids). This is true for some of the most famous theropod of dromaeosaurid — feathered relatives of birds. Thus, the discussion of the ecology of the Arctic predatory dinosaurs almost never carried out for lack of material.
Many findings of fossil remains in Alaska were made in formation Prince Creek (Campanian and Maastrichtian tiers, upper Cretaceous). Now it is located at 70 degrees North latitude, and in the time of dinosaurs was still at 13 degrees North. There the Texas and Alaskan paleontologists headed by Alfio Alessandro Chiarenza (Alfio Alessandro Chiarenza) from Imperial College London in the years 2005-2014 were excavated in which was found a small fragment of jaw with two teeth and several dental alveoli on it. Only one tooth grew fully, and he edges were serrated, which showed light and fluorescence microscopy.