Thorn-bush Predator

An unnamed species of non-sapient predators inhabited the Earth's moon Luna billions of years ago, when Luna was a temperate world with a breathable atmosphere and wasn't yet tidally-locked.

Biology
They're large creatures with red plated armor which can roll themselves into a perfect sphere about five feet (~ 1.52 meters) in diameter and move around by rolling. They have six retractable black tentacles, each about 12 ft long (~ 3.65 meters), with hooked claws and mouths at the end, which are used to suck out their prey's body fluids. They have six eyes, located at the base of each tentacle.

They live in the forests of thorn-bushes and create passages where the soil is hardened by their constant rolling over it. They're described as unintelligent, but capable of resisting the Mothers' psychic abilities due to their armor.

Although they don't seem to hunt in groups, they can send out drum-like calls to attract other members of their species when they're in danger, and band together against challenging prey.

Appearances

 * "The Moon Era", by Jack Williamson (1932)