Caitian
Caitians are a predator-evolved sentient species that humans consider :"cat-like" and are one of the earlier members of the Federation.
Species Physiology

Caitians are usually in the same range as humans for height with the female Caitians being slender and willowy of build. Caitians are covered with light fur and their fur color is usually in the brown-orange range but can vary considerable especially among Caitians born off of Cait, the exact reason for this is unknown. Some Caitians can grow their hair longer on their head, some have what might be termed manes, and other wear their longer hair in styles reminiscent of the other races.
Evolving from predators, the Caitians retain all of the tools of that heritage, claws at the end of their hands and feet and teeth optimized for the tearing of flesh. The Caitian eye gather more light than the human eye allowing for better night vision but as the expense of some fine color definition in their perception. Their senses of hearing and smell remain above the human norm and some Caitians have exceptional perception with these senses.
Caitian have expressive, but non-prehensile, tails which can make adapting Starfleet uniforms (and even chairs) necessary for their comfort. Many Caitians prefer not to wear footwear unless required by hostile environments.
Caitians and Kzinti seem to have some common ancestry but the exact nature of the ancestry and how the two races came to deveolp separately remains highly disputed.
Culture
Arising from cooperative hunting prides, Caitians built from smaller to larger groups selecting a representative to the next larger group and so on. This proved remarkably adaptable and, by the time they contacted the Federation, Cait was ruled by a functioning democracy.
Since joining the Federation, Caitian culture has begun to fragment along traditionalist against cosmopolitan lines.
The Traditionalist cultural faction extols traditional Caitian virtues of such thing as living close to nature, hunting for one's own food, and other such tradition that date to the pre-spaceflight Caitian lifestyle. A small radical faction of the Traditionalists advocate complete withdraw from the Federation but they are very much a fringe minority.
While the Cosmopolitan cultural faction has embraced Federation culture in all of its variety. They are as happy, if not happier, with replicated food and modern technology. Most cosmopolitans do not disparage the Traditionalist way of life but it is something they wish to experience only in small doses (if at all).
Among all Caitians, physical fitness is highly prized and almost all Caitians find some sort of athletics that they enjoy to channel this cultural expectation.
Language
The Caitian language is terse, originally designed to convey information when hunting. It has become more expansive as the Caitians become a technological species but basic concepts can be communicated very quickly when needed.
When speaking Federation Standard there is a often a "purr" in Caitian voices that some people find pleasing.
Food
Caitians are carnivorous by evolution and many provide their meat fresh and raw which can make dining with them in a traditional setting uncomfortable for some people. Some Caitians even have "larders" of live prey animals for personal use.
Food replicated for Caitians on Starfleet duty tend to retain the texture but not the appearance of fresh meat so as not to disturb their crew mates.
Family units
The extended family, sometime referred to as a Pride, is the core organizational unit in Caitian society. Individual Prides were originally organized by geographical area but now can also be built around a profession or even a starship.
History
Lost in the mists of historical debate are the origins of the Caitians and the Kzinti which share common ancestry even if are not longer inter-fertile.
The Caitians has achieved warp capable starships by the 22nd Century which brought them into contact with the Betazoids. Before meeting with the Federation, the Caitians had already had contact with both the Ferengi and the Orions which may explain their choice to join the Federation as soon as possible. By 2249, the Caitian government was in negotiation to join the Federation and they were speedily admitted.
References: