The Slylandro are the only race known to live on a Gas Giant, which they call Source. They cannot travel through space due to their physiology, though they have bought a self replicating Probe (Catalog Item 2418-B) from the Melnorme to explore space for them and report back to them. The Slylandro have had contact with the Precursors, the original Ur-Quan and the Sentient Milieu.
They are essentially sentient bags of gas that float through their homeworld's atmosphere. Their bodies are incredibly fragile. Because their world is devoid of non-gaseous materials they have no native construction, technology or written records. Their vision is in a range that is different from most races and it is to their great dismay when they realize that they are transparent to human vision.