Biology-

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.

Physiology-

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.

Ammonia Biology-

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.


~ Totally not ripped off from the Wiki...