Hydrurga leptonyx

The Leopard Seal.  A large, phocid native to Antarctica and the surrounding waters, and it has been known to inhabit the coasts of Australia, New Zealand, and Southern South America.  It is also known as the Sea Leopard. 
Leopard Seals are notorious for their predatory behavior, eating fish, krill, penguins, and even other seals.  They have an aggressive temper, and have even been known to attack humans.  Their only consistent predator is the Killer Whale (Orcinus orca).
Female Leopard Seals are known to grow larger, up to 3.6 meters (12 ft) and with a weight that is from 200 to 600 kilograms (440 to 1,320 lb).  They are often solitary, only getting together to mate.