Giant fossa

Fossas (pronounced foo-suh) are a cat-like ambush predator native to Madagascar that are actually related to mongooses. They grow to be two to four feet long and are the largest mammalian predator on Madagascar. 

Although they are generally thought to only grow to an average of three feet long, sightings of an unknown species or variant of much larger fossas have been reported. Besides their size of 9 ft, these giant fossas appear identical to normal fossas, although they are said to hunt much larger prey, like cattle and even humans. 

The first mention of giant fossas was by Admiral De Flacourt in 1658, who described an animal called an antamba (the Malagasy word for fossas), that were round-headed leopard-like animals the size of large dogs. He claimed that they were powerful enough to take down cattle. 

In 1999 a large number of sightings of giant fossas occurred, and an expedition was sent out to find them. They were unsuccessful at capturing one but did find fossa tracks three times the normal size. Giant fossas may be Cryptoprocta spelea, a species of fossa that reached 10 ft long that died out as recently as the 14th or 15th centuries.