Uranian (The Planet of Doubt)

"I don't think habit or training or discipline could ever account for the way that file of creatures acted, rushing and stopping and veering and circling, all in perfect unison. The whole line must have been under the direct neutral control of the leader - hearing and smelling what he heard and smelled, even, perhaps, responding to his desires, hating with him and finally fearing with him!"

- Patricia Hammond, 2100.

The Uranians, a.k.a. "Chains", are a peculiar form of life indigenous to the planet Uranus.

Biology
They are large, cylindrical creatures, about eight feet in length and six in diameter, and move on top of three pairs of short legs. Their skin is black and so are their body fluids. The front part of their bodies contains a kind of sense organ, which looks like a stem with a suction disk at the tip. The disk's edges move constantly and are capable of detecting distant and nearby objects by some means - probably either echolocation, scent or both.

As they live in a perpetually fog-covered environment, the Uranians are blind. They also have some means of producing vocalizations, as it's been noted that they emit a "keening note of pain" when shot.

What is most extraordinary about this species, however, is that they behave in the same way as processionary caterpillars. Individual Uranians march behind each other in close proximity forming long chains, and can actually link their bodies via their disk-shaped organ. When they do so, the disk behaves like a neural terminal, linking the nervous system of the two creatures and allowing the "guiding unit" (i.e. the one up front) to transmit information directly to the ones behind it. This in turn allows the entire chain to behave as a single organism, whose movement resembles that of a giant millipede. Individuals are still capable of surviving on their own when disconnected, but when connected, they have no individual will.

Killing an individual unit causes it to disconnect itself, which can be either useless or very bad if one's intent is to kill the whole thing. If the unit killed was the guiding one, it just means that the second one will assume command. If it was at the middle, however, its death will cause the chain to be divided in two, and the result will basically amount to having two superorganisms, rather than one.

Life cycle
While nothing is known about the Uranians' reproduction, it has been theorized that, like the processionary caterpillars, they're not mature organisms, but the larvae of the unidentified flying creatures which dwell in Uranus' atmosphere. Sadly, nothing is known about said creatures, as they've never been observed up close and are usually seen as nothing but shadows and silhouettes in the fog. Even their actual appearance is unknown.

Appearances

 * "The Planet of Doubt", by Stanley G. Weinbaum (1935)