"Juan Acavar's Smilodon" or "Mutant Jaguar" was a large jaguar like cat shot in South America in 1975.
After being shot and killed, it was examined by qualified zoologist Juan Acavar, who determined it to be a living species of Smilodon. However, to stop paranoia, he stuck with the jaguar identification.
More recently, there has been speculation that the animal was actually Thylacosmilus. However, Thylacosmilus looked signicantly different.