Twi'lek

The Twi'leks, also called Rylothians, were a humanoid, sentient species of mammals native to the planet Ryloth. They were easily recognized by their lekku, which hung from the back of their heads, occasionally curling around their shoulders. Female Twi'leks were commonly sold as slaves throughout the galaxy.

Biology and appearance
Twi'leks, like other members of genus Homo, were biologically very similar to humans. They featured five digit limbs, a humanoid form, and an almost identical internal anatomy. Anatomical differences included their sub-stomach, unique nervous system, generally higher body temperature, and higher metabolism. Physical differences included their colorful complexions and smooth skin, but most notably their lekku. These external organs, which were fully developed after puberty, had many purposes, both biologically and in everyday life. The Ryl language partly used subtle movements in the lekku to communicate. As lekku also stored fat, Twi'leks with corpulent lifestyles often inadvertently grew extras. The lekku also stored part of their complex central nervous system, housing several sensitive touch receptors and repressed subconscious memories. Although male Twi'lek's had identical auditory systems to humans, females featured two conical aural organs, in similar appearance to horns, which were weaker in hearing.

Twi'leks were viviparous, and mated all year round. They were capable of interbreeding with other members of their genus. Due to their high metabolism, and two stomachs, female Twi'lek generally developed larger breasts, storing more milk than the average human.