Hawkinsite

Hawkinsites are a sapient, spacefaring species of quadrupedal herbivores from Hawkin's Planet.

Biology
Hawkinsites are herbivorous with a somewhat bovine appearance, and evolved from plains-dwelling ungulate ancestors on a world with higher gravity than Earth. They have two arms and four legs. Their hands have four dexterous fingers and no thumb, which is compensated by the fact that the fingers have five joints each, and end in tiny vestigial hooves. Their yellowish skin is hard, dry and ridged, and feels hot to Human touch. They have large lipless mouths with no incisor teeth, and make whistling sounds when they speak, but are otherwise perfectly capable of speaking Human languages. Their jaws move from side to side when they chew, similar to Earth ruminants. Their eyes blink to express surprise or humor.

Their biology is carbon-based and they can consume Earth plants without problem. Their metabolism is also affected by alcohol. While they breathe oxygen, they also require small amounts of hydrogen cyanide in the atmosphere, which is produced naturally by microorganisms on their homeworld. The cyanide is vital to keep their blood cells functioning. Deprived from it, they would suffocate in less than an hour. Due to the absence of iron or other metals, their blood is entirely colorless.

Hawkinsites are biologically immortal and never stop growing, although growth rate does slow down considerably upon reaching adulthood, to the point that, eventually, they grow only about an inch every 15 years. Six feet two inches (~ 1.88 m) is considered an unremarkable size for an adult, even though they often live several centuries. Sleep is unknown to them, although they can voluntarily enter a similar state by disconnecting their conscious minds from their bodily functions, thus entering in a state of deep contemplative meditation and relaxation that can last for days. Despite being dormant, their mental processes remain unaltered during that period, and they do not dream.

Hawkinsites possess a mysterious sense of awareness of each other's presence, which becomes particularly strong in individuals that share a close emotional bond. They are constantly aware of their friends and relatives' location, no matter where they are on the planet. The only situation in which they cannot feel each other's presence is if they're on different planets.

Culture and society
Hawkinsites are regarded as unsociable towards other species (or at least towards Humans) and prefer to interact with their own kind. They have a social caste system and rarely associate with members of different castes. They have no concept of marriage.

Appearances

 * "Hostess", by Isaac Asimov (1951)