Takaran

From Memory Alpha, the free Star Trek reference

You may also be looking for a group of primitive humanoids who referred to themselves as the Takarians.

The Takarans are a humanoid species native to the planet Takara.

Takarans are characterized by a very unusual anatomy and physiology where their internal organs are not as distinct as those of most humanoids – their organ systems are much more evenly distributed around their bodies, resulting in Takarans having a very high resistance to injury. Takarans also have voluntary control over their own physiology down to a cellular level and can place themselves in a form of stasis resembling death.

To Starfleet medical equipment, only the rate of cellular decay could verify whether a Takaran was dead or alive – a slow rate of cellular decay was indicative of a Takaran in voluntary stasis; the rate of cellular decay would be much faster if the Takaran were truly dead – this was unknown to Doctor Beverly Crusher until 2369.

Takarans are also able to put only a part of their body in stasis at a time, enabling them to slow injury in specific areas and thereby reduce the overall effects of the injury. (TNG: "Suspicions")

Since Dr. Crusher knew little of Takaran physiology and also stated Jo'Bril was the first Takaran she'd ever met, it is unlikely that Takarans were Federation members as of 2369.