The Ursus maritimus tyrannus measured 1.83 meters and an average mass of more than one ton (1200 – 1500 kg), making it almost three times as heavy as an adult male brown bear.
This fossil subspecies evolved from an isolated population of Arctic brown bears in the late Pleistocene and was the largest carnivorous land mammal of all time .
Since the oldest fossil is 100,000 years old, it is estimated that they evolved between 100,000 and 250,000 years ago, from a population of Arctic brown bears, probably isolated by glaciation.
The contemporary descendant of this enormous creature is the largest bear today, the polar bear : the adult male has a mass of 400 – 600 kg and measures up to 2.6 meters in length from nose to tail.
The species lives in latitudes 65 – 85º N, making it the northernmost bear.
Also in the land mammal with the most extensive habitat : the adult polar bears of Hudson Bay, Canada, have vast territories of up to 350,000 square kilometers, about the size of Germany.
Under the coat is the skin, which is black to better attract solar radiation and thus increase body heat. Ordinary light reflects off the coat, usually creating the false sensation of whiteness. However, at certain times and places it may appear yellowish or even light brown .
By the way, the most nutritious bear milk is also that of the polar bear : it contains up to 48.4% fat and is vital for cubs, which must survive in a freezing environment.