Simplify the following text for a Grade 9 native English-speaking person.
Original: The Siberian tiger ( Panthera tigris altaica ) , also known as the Amur , Altaic , Korean , North Chinese or Ussuri tiger , is a subspecies of tiger which once ranged throughout Western Asia , Central Asia and eastern Russia , and as far east as Alaska during prehistoric times , though it is now completely confined to the Amur-Ussuri region of Primorsky Krai and Khabarovsk Krai in far eastern Siberia , where it is now protected . It is the biggest of the eight recent tiger subspecies and the largest living felid , attaining 320 k in an exceptional specimen .
Simplified: The Siberian Tiger ( Panthera tigris altaica ) , also known as the Amur Tiger , Manchurian , or North China Tiger , is a subspecies of the tiger , of the Felidae family .