Slinker

The Slinkers (Mus sapiens) are six-inch long semi-sapient creatures native to Jupiter's satellite Io. Creatures that might be the same species as them have also been spotted on Mars, but how they got there is unknown.

Biology
Slinkers have tiny red eyes and are known to produce squealing sounds. Their overall appearance is similar to a black rat wearing a membranous cape - which actually consists of a cowl of loose skin. They also have a mildly venomous bite.

Culture and society
On Io, Slinkers live in stone-made villages which resemble miniature models of medieval towns, some of which are known to war with each other occasionally.

Members of this species, or a very similar one, have also been found scurrying over semi-abandoned Thoth cities on Mars and reading ancient books there. Assuming these are indeed Slinkers, the most likely explanation for this would be that the old spacefaring Thoths have visited Io at some point and Slinkers were brought back to Mars in their ships, intentionally or otherwise. Modern Thoths seem to actively hate the Slinkers, suggesting some kind of conflict took place between the two species.

Appearances

 * "Valley of Dreams", by Stanley G. Weinbaum (1934)
 * "The Mad Moon", by Stanley G. Weinbaum (1935)