The Erelynians were a species from Erelyn IV whose entire population was killed by radiation from the supernova that created the Crab Nebula thousands of years ago.
Several years before the supernova, the Erelynians had mapped the Crab star system and were on the verge of creating a form of warp drive, although the politicians on the planet cancelled the project. When the supernova occurred, the radiation wiped out the Erelynian race, but the accomplishments of the Erelynians, including their cities and technologies, survived and were later studied by the Vulcans. It was believed that if the warp project had gone ahead, the Erelynians could have learned of the impending supernova and taken steps to save their race. (DS9 - Millennium novel: The War of the Prophets)
An Erelynian cryogenic capsule.
In the 24th century, it was discovered that a few Erelynian individuals did manage to create a functioning warp drive and escaped moments before the rest of their civilization was destroyed. The body of one such individual was later found preserved in a cryocapsule, together with a number of Erelynian artefacts. (ST video game: Infinite)