Superficially resembling a cross between a large rabbit and a turkey, Avali stand bipedally, with digitigrade poise. They are covered from head to toe in feathers of varying length, possess two large wings with rudimentary digits at the wrist/hand enabling them to manipulate objects dexterously, while also possessing 4 long, rabbit-like ears.
Avali are not mammals, but instead more similar to prehistoric Earth dromaeosauridae. Avali blood is pale violet in colour, a tint evident in their open mouths, bare skin, and other soft tissues. Male and females are most easily told apart by their feathers, as there are no other external differences. Females tend to have muted, two-tone feathers, often with speckled patterns, while males have brightly coloured, iridescent bands across much of their body.
The avali are superficially similar to dromaeosauridae of ancient Terra. A typical adult avali stands around 1-1.2 meters tall, and laid out, 1.5 to 1.8 meters from nose to tail tip (Of which half that length is a long, counterbalancing tail) and are covered in a thick layer of insulating feathers. Their wing feathers allow full flight on Avalon, with it's low gravity and thick atmosphere, but are far less useful on higher gravity worlds. Avali on other planets are often only able to make controlled glides and break falls on their own, and cannot truly fly unaided.
Unlike humans, the Avali rely on liquid ammonia as the primary solvent in their biology, which makes them extremely well adapted for cold environments, but renders what humans consider Goldilocks worlds similar to Earth intolerably hot. It is important to note that the Avali are still carbon-based organisms; their systems merely use liquid ammonia instead of water.
The boiling point of ammonia under standard pressure is -27 Fahrenheit/-33 Celsius. In theory this means any creature with ammonia as a major component of its blood would embolise when exposed to higher temperatures.
However, this is only true under "standard conditions". Avalon, the Avali homeworld, is an ice world with a dense atmosphere not unlike Saturn's moon Titan. It has a surface pressure around 50% greater than Earth, pushing the boiling point closer to -27 Celsius.
Secondly, Avali feature a range of biological adaptations, including improved arterial pressure, thick insulation, and trace amounts of water in solution, that further raise the boiling point.
Their pressure adaptations are so extreme, however, that they struggle to survive in the polar regions of their own world without proper protective clothing. Their body fluids will freeze quicker than expected in extreme cold, which is why they typically thrive in the proportionally 'warmer', arid, icy tundras of their own world.
Like terrestrial birds, they possess a range of specialized feathers: their upper body feathers are slicker and oilier to protect from snowfall, while their lower body has lighter, fluffier down feathers that helps insulate the core body. They also possess pulviplumes, specialized down feathers that regenerate continuously. The outer barbules break off and help to oil and powder the other feathers, keeping them in pristine condition. This same "powdering" mechanism has the interesting effect of also treating fur, making fur hide a popular clothing lining.
Their crest feathers (those on the back of the head), respond well to the application of heat, causing them to curl towards the heat and become permanently deformed. In this way it is possible to "style" their crest feathers in a way analogous to hair styling.
The long feathers, such as those on the arms and crest, have a healthy blood supply at their roots and can bleed profusely if they are broken off or pulled out, though this does not pose a significant health risk. Feathers lost in that way will regrow after several weeks.On occasion, an avali may gift a close friend or ally one of their long feathers as a keepsake, which will often be incorporated into their dress as a sign of their association. For example, an instructor may gift a feather to a recently graduated pilot, showing the instructor's recognition and approval.
While the Avali possess large eyes, this is purely to provide some measure of eyesight in the very low light levels of their homeworld; their primary sense is hearing. Their four long, independently mobile ears can pick up sounds from multiple directions at once. Avali auditory processing is capable of tracking multiple sound sources simultaneously. This uncanny hearing gives the impression of blind sight, being able to "spot" and track creatures outside of line of sight. It also enables them to converse in parallel with their pack-mates, each member serving as a separate processor to find a resolution to the topic at hand.
Reproduction, Sexuality & Growth
Physiologically, both sexes of Avali are extremely similar; both possess a cloacal vent, and males lack the genitalia seen in terrestrial mammals. Instead, genetic material is passed the same way as seen in terrestrial birds.
After fertilization and a short gestation period, the female will lay a single large, soft, leathery egg. The amount of nutrients required for the production of an egg and eventually a baby makes large clutches impossible. Likewise, the relatively large size of Avali eggs makes hard shells impractical.
Eggs are left in the care of a communal hatchery, where the young kits are then raised and educated by the tribe rather than their natural parents. Avali eggs typically take 4-5 months to hatch.
Virtually all Avali possess some degree of cybernetic augmentation; at a bare minimum they possess a neural interface that provides augmented reality support and allows them to interface with the Nexus and compatible hardware and medical nanites that can help monitor and isolate life threatening conditions or trauma.
More advanced cybernetics include life support regulators that help with surviving on more exotic worlds, limb replacements, or even total body replacement; popular among career soldiers and explorers since a cyborg body can withstand far more extreme environments and/or survive massive trauma without permanent injury to the operator.