Ursus maritimus tyrannus (meaning tyrant polar bear ) is an extinct subspecies of polar bear , known from a single fragmentary ulna found in the gravels of the Thames at Kew Bridge , London . It was named by the Finnish paleontologist Björn Kurtén in 1964 and is interpreted to represent a relatively large subadult individual: the ulna is estimated to have been 48.5 cm (19 in) long when complete,  for comparison, modern subadult polar bear ulnae are 36–43 cm (14–17 in) long. 
Roman Uchytel’s galleries constitute the first resource solely dedicated to the reconstruction of prehistoric animals beyond the dinosaurs. These are not photographs, but rather, artistic recreations from the skeletons of ancient animals that roamed the earth millions of years ago. Many of these fascinating creatures are unfamiliar to the public and remain a mystery even to science.