A Pygmy tyrannosaur was one of the top predators of the late Cretaceous North America's high latitudes. It is speculated that the diminutive size was an adaptation to the harsh polar climate. There is almost no doubt, although no physical evidence was recovered, that the theropod had been covered with proto-feathers, or so called "dino-fuzz".
A free paper:
Anthony R. Fiorillo & Ronald S. Tykoski (2014)A Diminutive New Tyrannosaur from the Top of the World.
PLoS ONE 9(3): e91287.
"Tyrannosaurid theropods were dominant terrestrial predators in Asia and western North America during the last of the Cretaceous. The known diversity of the group has dramatically increased in recent years with new finds, but overall understanding of tyrannosaurid ecology and evolution is based almost entirely on fossils from latitudes at or below southern Canada and central Asia. Remains of a new, relatively small tyrannosaurine were recovered from the earliest Late Maastrichtian (70-69Ma) of the Prince Creek Formation on Alaska's North Slope. Cladistic analyses show the material represents a new tyrannosaurine species closely related to the highly derived Tarbosaurus+Tyrannosaurus clade. The new taxon inhabited a seasonally extreme high-latitude continental environment on the northernmost edge of Cretaceous North America. The discovery of the new form provides new insights into tyrannosaurid adaptability, and evolution in an ancient greenhouse Arctic."
By the way, one of my favourite old movies:
Emperor of the North Pole (the title was later shortened to Emperor of the North) from 1973. It is an American film directed by Robert Aldrich and starring Lee Marvin, Ernest Borgnine, and Keith Carradine. The poster for Italian distribution: