Even before the start of Star Trek: Discovery, Ambassador Saru (Doug Jones) had a fascinating life. Saru is Starfleet’s first Kelpien, a new species created for Star Trek: Discovery. Because Star Trek: Discovery is set 5 years before Star Trek: The Original Series, there had to be a good reason that Kelpiens didn’t appear elsewhere in the Star Trek timeline. As part of a companion series to Star Trek: Discovery, Star Trek: Short Treks season 1, episode 3, “The Brightest Star”, explains why Saru was Starfleet’s only Kelpien for centuries.

https://screenrant.com/star-trek-discovery-saru-fascinating-life-explainer/