Steller's Sea Cow: the defenseless beast (extinct since 1768)Steller's sea cow was a large herbivorous marine mammal. In historical times, it was the largest member of the order Sirenia, which includes its closest living relative, the dugong (Dugong dugon), and the manatees (Trichechus spp.). Formerly abundant throughout the North Pacific, its range was limited to a single, isolated population on the uninhabited Commander Islands by 1741 when it was first described by Georg Wilhelm Steller, chief naturalist on an expedition led by explorer Vitus Bering. Within 27 years of discovery by Europeans, the slow moving and easily captured Steller's sea cow was hunted to extinction.
Irish Deer: the largest deer that ever lived (extinct about 7,700 years ago)The Irish Elk or Giant Deer (Megaloceros giganteus), was a species of Megaloceros and one of the largest deer that ever lived. Its range extended across Eurasia, from Ireland to east of Lake Baikal, during the Late Pleistocene. The latest known remains of the species have beencarbon dated to about 7,700 years ago.Although most skeletons have been found in Irish bogs, the animal was not exclusively Irish and was not closely related to either of the living species currently called elk - Alces alces (the European elk) or Cervus canadensis (the North American elk); for this reason, the name "Giant Deer" is used in some publications.
Caspian Tiger: the third largest (extinct since 1970)The Caspian tiger, also known as the Persian tiger, Turanian tiger, Mazandaran tiger,or Hyrcanian tiger was found in Iran,Armenia, Azerbaijan, Iraq, Afghanistan, Turkey, Mongolia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan until it apparently became extinct in the late 1950s, though there have been several alleged sightings of the tiger in the more recent years.First thought to have been its own distinct subspecies, genetic research in 2009 proved that the animal was closely related to the Siberian tiger (P. t. altaica). Separated by only one letter of genetic code,[dubious – discuss] it is believed that the two split off from each other only in the past century. Some researchers[who?] suggest that it may be possible to reintroduce the closely related Siberian Tiger to the Caspian tiger's historical range in hopes of recreating this now-extinct big cat.
Great Auk: largest of all auks (extinct since 1844)The Great Auk, Pinguinus impennis, formerly of the genus Alca, was a large, flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus Pinguinus, a group of birds that formerly included one other species of flightless giant aukfrom the Atlantic Ocean region. It bred on rocky, isolated islands with easy access to both the ocean and a plentiful food supply, a rarity in nature that provided only a few breeding sites for the auks. When not breeding, the auks spent their time foraging in the waters of theNorth Atlantic, ranging as far south as the New England region and northern Spain through Canada, Greenland, Iceland, Faroe Islands, Norway, Ireland, and Great Britain.
Cave Lion: one of the largest lions ever (extinct 2,000 years ago)The cave lion, also known as the European or Eurasian cave lion, is an extinct subspecies of lion known from fossils and a wide variety of prehistoric art. This subspecies was one of the largest lions. An adult male, which was found in 1985 near Siegsdorf (Germany), had a shoulder height of around 1.2 m and a length of 2.1 m without a tail, which is about the same size as a very big modern lion. This male was even exceeded by other specimens of this subspecies. Therefore this cat may have been around 5-10% bigger than modern lions. It apparently went extinct about 10,000 years ago, during the Würm glaciation, though there are some indications it may have existed as recently as 2,000 years ago, in the Balkans.