Nautiloid

Nautiloids are a sapient aquatic species from a large oceanic world in the central area of the Milky Way Galaxy. They evolved long after mankind.

Biology
Nautiloids evolved in the shallow seas along the coastlines of their world's numerous archipelagos. Their ancestors were small mollusk-like herbivores whose boat-like shells and sail-like membranes allowed them to drift over the sea surface while foraging. From this ancestor sprouted several species, some of which became increasingly larger and more adept at navigation, until one of them developed sapience.

The Nautiloids can be best described as living organic sailing ships, which dwarf in size even the largest of Earth's whales. Their shells are shaped like the hull of a 19th century clipper, with a pair of long manipulatory tentacles at the fore end, which are folded when not in use. A mobile fin-like organ at the rear end can be employed as a rudder or propeller, while a complex system of bony masts and membranous sails allows them to navigate with the wind. The sails can be yellow or russet in coloration.

Nautiloids have a pair of downward-looking eyes on each side of the prow and additional eyes on top of the principal mast. A specialized organ inside their brains is sensitive to the planet's magnetic fields and gives them an innate sense of orientation. Hearing and gustatory organs are placed beneath the water line and used to detect potential prey, as well as deduce the configuration of the sea bottom by echolocation. Their diet is omnivorous. They produce underwater sounds for short-range communication and use a mobile tentacle on their masts to send semaphore signals for long-range communication.

In spite of their mollusk-like nature, reproduction in this species is typically mammalian. Males pursue females and grapple them in order to copulate with them. They are viviparous and always give birth to a pair of children, one of which is born from the port side and the other from the starboard. Mothers take care of the children, which are suckled at her flanks.

Culture and society
Like most sapient species, Nautiloids live in communities and often collaborate with each other in fishing and practicing agriculture. Their technology includes fishing nets and traps, stone harbors and workshops, windmills, canals to penetrate land, the use of volcanic heat for metallurgy, cannons, concrete, and even solar panels.

Appearances

 * Star Maker, by Olaf Stapledon (1937)