Caitans

The Caitians are a humanoid species hailing from the planet Cait. The feline appearance of Caitians includes long manes and a tail. Caitians tend to vary in color from brown to black, and talk in a soft purring voice. (Star Trek: The Animated Series)

As Cait is a Federation member, Caitians are known to serve in Starfleet and on the Federation Council, and were present as members in 2286. (Star Trek IV: The Voyage Home)

The name of the species comes from a biography of Lt. M'ress published by Lincoln Enterprises in 1974, which claims that the Caitians are related to the Kzinti.

The Caitians are expanded upon in FASA's Star Trek IV Sourcebook Update, which indicates that the feline humanoids seen in The Voyage Home were intended to be the same species.