Savage Earth: Cold Moon
Cargo beast is the common name for the varied species of Litopterna, a simplistic title given their popularity as pack animals and beasts of burden. They are hoofed mammals common to South America (and which have been transplated to North america) where they evolved in isolation during the time that the region was an island continent.
the jungles and mountaisn of South America make the wheel almost worthless and large cargo beats are the backbone of the Old empires trade and transport. Even in North america more cargo beast caravans are employed than are the carts and wagons of Europe. They are bred in great numbers and small fortunes are ploughed into keeping both captive and wild stock safe from the various large predators of the Americas.