Random concept for a species I thought of. Tree Runners are large mammals who spend much of their life in trees. Wide paws, curved claws, strong legs and spikes on their tail help them to bound vertically up trees. They are flexible and have long tails to help them balance. Wings allow them to fly from tree to tree and travel longer distances if need be, and their thick, fluffy coat insulated them from wind chill. Their peculiar manes are made of stiff (yet still soft) fur that provides extra warmth for their neck and makes them somewhat more aerodynamic. Full grown Tree Runners are a similar size to cows and horses, so domesticated individuals can be saddle trained and carry their owners with them up trees or durning flight (though special care should be taken to ensure they are strong enough to do so - you should never attempt to ride an untrained Tree Runner as it can be dangerous for the both of you).
Anyways, would anyone be interested in adopting these if they became a species?