Raklu (RAK-loo)
It is uncertain what species may have combined to create the desert animal known as the Raklu. Scaled like a desert lizard, but large, and warm-blooded as well, it resembles no particular four-footed animal of that region, and may be a spontaneous creation of magic instead.
Originally a wild species in the canyons of Kubara, the locals were able to domesticate them for their own needs, as Raklu are highly intelligent and quick to train. The shorter, more agile ones were bred for herding goats and sheep, while the larger, bulkier Raklu were used to pull goods on travois sleds or carry packs strapped to their backs. Eventually, there developed two distinct breeds of Raklu, distinguishable by their coloration and conformation. Pack Raklu have much more distinct orange coloration to their scales, while herding Raklu are pale orange, or almost white in daylight.
At night, only size distinguishes the two breeds. Their light colored scales, useful for reflecting the heat of the sun away from themselves, darken as night comes on, to a near-black, conserving heat through the cold desert nights. These scales are not connected to each other directly, either. During the day, Raklu expand their sides, causing small gaps between the scales, allowing the blood vessels that flow through to create an evaporative cooling system that releases stored heat to the outside. At night, the scales are tightly closed, once again conserving heat.
The Raklu is an herbivore and can scavenge on even the toughest scrub brush, not unlike the goats and sheep that they herd. They require little water, able to go all day without a drink, and are very efficient at recycling their own bodies' water, urinating only once every few days.
Today, domesticated Raklu are an important staple in the Kubarin way of life. Without their aid in corraling and driving the tribes' herds, and in transporting the nomads' goods from oasis to oasis, the desert wanderers' lifestyle would not exist.
That's a really cool thermoregulation method! Awesome little guys.