Leyen are sentient crepuscular bipeds native to lijin kovt, the fourth planet of Δ Pavonis. They are similar in hight and build to humans, but their skin has a mottled appearance in various shades of brown, grey and green - something like camouflage fabric. Their skin is covered with vibrissae, light but stiff bristles which are approximately two inches long and an inch apart. These make them highly sensitive to air movements. This sense is very important to them, and gives them a sense of being fully immersed in an active world. Cognitive exolinguists believe that this explains why nouns and verbs are fused in iljena. Visually, they can see a wider range of wavelengths than humans (extending into the near infra-red), but only discriminate colours over a narrower range of frequencies. Their sense of smell is better than humans.
Viviparous fish, with life-cycles similar to that of a seahorse (eggs are kept in a brood-pouch by the male until hatching) are very common in lijin kovt's oceans, and one such species was the ancestor of land-dwelling vertebrates on lijin kovt (Terran biological terms are used analogically for reasonably similar creatures). The basal clade of land vertebrates is therefore known as "patrigenes" in human terminology. As larger creatures evolved, larger eggs were necessary, and trasferring the eggs between the female and the male became difficult. The "macroovan" clade developed two different strategies to solve this problem. One group, the "neoovipares" began to lay shelled eggs. This group includes the Pavonian equivalent of birds. The other group, the "matrigenes", retained the egg within the females body, continuously secreting yolk to nourish it until birth. It is to this group that the Leyen belong.
During infancy, Leyen are fed regurgitated food from a crop by both parents. The presence of a crop in males is an adaptation to a monogamous lifestyle - in related species that are not monogamous, the male crop is vestigial.
Leyen do not have visible secondary sexual characteristics - they normally distinguish male from female Leyen by scent. This means that they do not need clothing for personal modesty. As it would interfere with their vibrissae, they will only wear clothing if absolutely necessary to protect the body.