Terrafelis

Terrafelis are a species that resembles a common hosue cat except with opposable thumbs and the ability to walk upright. Most have a height of no more than two feet tall.

Terrafelis became the dominant species on Earth after it was abandoned by humans millenia ago, during which time nearly all human made structures on the planet except for Mt. Rushmore had long deteriorated. They cannot breathe the same atmosphere as humans, so when exploring off-world, they must wear breath masks. This is because in the time humans had been away from Earth, the planet's atmosphere changed drastically. The Terrafelis adapted to it over time but humans did not.

Terrafelis live as hunter-gatherers although they tend to congregrate around Mt. Rushmore, which they refer to as the Old Watchers.