Scalos

Scalos was an uninhabited planet. This was the homeworld of the Scalosians, an extinct humanoid species. This planet was located in an outer quadrant of the galaxy.

This was one of the planets where all humanoid life went extinct; four others were Cheron, Exo III, Kataan, and Zetar. 

When the USS Enterprise (NCC-1701) was charting this quadrant, the starship picked up a distress call coming from an unknown world, A landing party discovered that the world was barren. There were no apparent animal life forms and sparse vegetation. According to the distress call, there were 900,000 Scalosians who lived in a nation; 113,000 of them lived in a city. Their civilization was rated 7 on the industrial scale.

After the world was devastated by volcanic eruptions that poisoned the water with radiation, the Scalosians became sterile and their numbers began dropping. When the planet was visited by the Starfleet vessel USS Enterprise (NCC-1701), only five hyperaccelerated individuals remained.