memory alpha
Multiple realities
(covers information from several alternate timelines)
The skeleton of a prehistoric animal

The skeleton of a prehistoric animal

"Unfortunately, extinction is often the natural end of evolution."
Captain Kathryn Janeway, 2372 ("Prototype")

Extinction was a term for the condition of a species of which there were no currently living members. Extinctions have occurred naturally on many worlds through the course of evolution, or through extinction-level events. Some species have become extinct through unnatural means.

In 2258 of the alternate reality, Spock initially planned to resign his commission, given what he perceived as the pending extinction of the Vulcan people, and help rebuild his species. Spock Prime urged him to continue to serve in Starfleet, saying he would fulfill this while young Spock remained where he belonged. (Star Trek)

Extinctions

Distant past

The skull of a Xindi-Avian, which went extinct in the mid-21st century

The skull of a Xindi-Avian, which went extinct in the mid-21st century

The fossil of ammonite featured in Star Trek: First Contact, auctioned off in Christie's 40 Years of Star Trek: The Collection auction, was suggested in the auction information that it wasn't an ammonite after all, but rather a representative of a long-dead civilization of intelligent mollusks. [1]

Pre-Federation

Recent past

Given that some Malurians had traveled to another planet over a century earlier, it is likely that some Malurians were off-world when their civilization was destroyed by Nomad.
The destruction of Vulcan in 2258 in an alternate reality presumably decimated or rendered completely extinct most or all of the indigenous plant or animal species, such as the sehlat, the Le-matya, the Vulcan marsupial, the Vulcan sandworm, and the Vulcan orchid.

Previously believed extinct

Salt vampires, previously believed to have gone extinct in 2266

Salt vampires, previously believed to have gone extinct in 2266

The destruction of Iota Geminorum IV presumably also rendered extinct all other indigenous species, including the reptilian species that naturally preyed on tribbles.

Extinction and the Prime Directive

Background information

Not all non-extant species were explicitly referred to as "extinct".

Borg assimilation and near-extinction

Species wholly assimilated by the Borg ceased to exist as a separate species, which was essentially equivalent to their extinction. Even species not quite entirely fully assimilated were so decimated that their extinction was either practically inevitable or considered so by remaining members.

For example, two species that the Borg almost entirely assimilated were Species 10026, though Seven tried to save a handful. It is highly likely that the few survivors ended up either dying out or later assimilated. (VOY: "Dark Frontier") Another is Species 116, which was essentially wiped out by the Borg, albeit with a few tens of thousands of (now homeless) survivors. To Arturis they were in essence wiped out as a species and too weak to regain viability. (VOY: "Hope and Fear")

Endangered

Aside from Borg assimilation, at least one Alpha Hirogen believed his race was becoming so nomadic and far-spread that they would soon become extinct. Other Hirogen, along with Captain Kathryn Janeway shared this view, which led them to create "holographic hunting space stations" – notwithstanding the fact that they backfired. (VOY: "The Killing Game", "Flesh and Blood")

The Kobliad were also said to be a dying race. (DS9: "The Passenger")

Following the destruction of Vulcan in 2258 in an alternate reality, Spock noted somberly in his log that he was now a member of an endangered species. (Star Trek)

While not explicitly referred to as such, the Tarellian species, which in 2364 was reduced to a single known ship crew infected by a virus for which no cure was known to exist, can presumably also be considered endangered.

The JahSepp believed their species was going to be completely killed due to an intruder in their realm. (DIS: "Saints of Imperfection")

The Ba'ul narrowly escaped extinction at the hands of evolved Kelpiens. (DIS: "The Sound of Thunder")

In an alternate timeline, the Vau N'Akat became endangered by the mid-25th century as a result of the Vau N'Akat Civil War. Blaming the Federation, The Order sought to travel back in time and destroy the Federation in order to prevent this from happening. However, only the Diviner and Asencia survived the journey. Armed with this knowledge, the USS Voyager-A and the USS Protostar intervened to help the Uprising overthrow Asencia when civil war did break out, before making peaceful first contact with the Vau N'Akat, thus altering the future and preventing the near-extinction of the species. (PRO: "Kobayashi", "A Moral Star, Part 2", "Preludes", "Ouroboros, Part I", "Ouroboros, Part II")

The Krenim and alternate timeline extinctions

As a result of timeline tinkering, many civilizations were referred to as "extinct" by Annorax and his weapon ship, including the Zahl, the Garenor, the Ram Izad, the Malkoth, and the Alsurans, until his timeship was destroyed, presumably restoring all of history. (VOY: "Year of Hell", "Year of Hell, Part II").

All of the above were only near or quasi-"extinctions". The only ones referred to as actual extinctions were ultimately restored upon the destruction of Annorax's time-ship. The others would probably be classified as "endangered" in today's nomenclature. The implicit exceptions were cases of total assimilation of a species by the Borg, though it is unclear how often this occurred.

External link