We're in the midst of the sixth great extinction right now, with the rise of humans being behind the unprecedented rise in the rate we're losing species.
ThylacineThe largest carnivorous marsupial in modern times (standing about 2' tall and 6' long including the tail), the Thylacine once lived in mainland Australia and New Guinea, by the time of European settlement it was already nearly extinct, due to human activity. In Tasmania however (hence, the more common name of Tasmanian tiger or Tasmanian wolf) it lived on, with the last one confirmed killed in the wild in 1930. The last Thylacine in captivity, pictured above, died in 1936.
That said, through the 1960s people suspected that the Thylacine may have held on in small pockets, with the final declaration of extinction not happening until the 1980s. To this day however, occasional reports of sightings surface in Tasmania and New Guinea.