Planet of Origin: Jupiter
The Jovians are a sentient species that built several advanced arrogant civilisations on their planet which, given the size of the planet, have not all made contact with one another. Although their technical science is on pair with that of Humanity, their knowledge of astronomy is lcose to nil, as they know about the existence of the sun and the four Galilean moons of Jupiter, but are ignorant over all other celestial bodies.
They are built around radial symmetry with tentacles and sensory organs allowing them to detect mass. Substances of low specific mass are transparent to them, allowing to see through the dense Jovian atmosphere as well as Humans see through Earth air. Oxygen is lethal to them, and they may drown if submerged in ammonia, which is known to form lakes in the vast islands where they built their cities.
For 25 years they had radio contact with Human settlers on Ganymede, but immediately cut contact when they realized they were dealing with non-Jovians, feeling sudden repulsion and xenophobia. Robots were later sent down to the planet in hopes of restoring contact.
Source: Isaac Asimov, Not Final! (1941), Victory Unintentional (1942)