This is not a complete write-up.
Quadrupeds, built for speed and nothing else. Their heads are long-muzzled and streamlined, with internal ears and an extra eyelid for going at high speeds. They have no whiskers and their nostrils are set on the sides of their muzzles, also for aerodynamics. Their tail is long, sinuous, and used purely for balancing. Even their fur is sleek and short, to better cut through the wind. Their chest is deep and their waist narrow, their spine is flexible beyond all reason and their ribs are narrow and also flexible, able to move with each stride. Their lungs are huge, as is their heart (hence the deep chest) to provide ample oxygen and blood when running. Their legs are incredibly long. Their forelegs are much like a cheetah's, with the shin bone and ankle elongated, and the toes on the dog-like paw much elongated and tipped with strong, curving claws for traction. Their hind legs are very powerful, yet lean, and can propel them over 30 ft into the air. Their hind legs have the same paws, yet instead of three long toes they have four, with the same claws. Their sense of smell and hearing are about wolf or lion standard, but their sight is fantastic (when not covered by the protective second eyelid) and they can see farther than an earth bird of prey. They're aren't very good fighters, relying on small fangs and narrow but razor-sharp teeth and their rather dull claws. They just run away from anything trying to kill them or, this one is more common, they'll run circles around their enemy until it either slinks off in confusion or gets dizzy and they can strike quickly. In hunting, it's easy - a band of hresahrs will form, and then they'll run the prey to death. Their fur is earth-toned, usually marked with darker or lighter small concentric circles.