Heptapod

Heptapods are an intelligent, space-faring extraterrestrial species in Story of Your Life and the 2016 film Arrival. In both works, their first contact with humans and Dr. Louise Bank's struggle to communicate with them serve as the plot and are used to explore themes about determinism, language and the Sapir-Whorf hypothesis.

Biology
As the name suggests, a heptapod has seven limbs, whose arrangement makes the creature heptaradially-symmetrical.

Communication and language
Heptapods use vocal communication that is unpronouceable by humans, and writing, which humans can learn.

Technology
Heptapods are more capable than humans when it comes to spaceflight. When they first contact with humanity, they use radio to transmit their vocal recordings.

Ships
Heptapod ships are 450-meter-tall, black metallic vehicles shaped like a half-circle. They apparently lack thrusters, implying that heptapods might possess a form of anti-gravity.