Reptomammals

I've made a few references to reptomammals before. Obviously, in real life there's no such thing; an animal can be a reptile or a mammal but not both. But reptomammals are a legacy of a Golden Age of  Technology at the dawn of the Old Kingdoms era, or even before. In contrast, Space Opera X takes place in what is relatively speaking a Dark Age. Genetically engineered wildlife that was part of the plan for terraforming worlds, reptomammals were created by these early people to serve as domestic animals as well as to be released into the wild to create stable ecosystems that would later benefit the colonists who were to settle on these terraformed planets. The gene-splicing technology that would allow these early spacers to create all new creatures with features from reptiles and mammals, yet uniquely adapted to these newly terraformed worlds is long lost, as is the terraforming process itself, but through good old fashioned animal husbandry and breeding, as well as the genetic malleability and instability of the reptomammals in general, they have yet developed into a varied and broad set of animals seen on most Colonial worlds, or even on worlds of "natives" who were there since the times of first contact.

Because of these broad similarities, people tend to use the same word to refer to differing creatures on various worlds that serve a similar function, or who were bred from what was apparently a similar (or even the exact same) reptomammalian template. The words are traditional and very old, and few people have the foggiest idea where they came from, but the roots of the words can be traced, again, to the earliest spread of Earth-descent humanity. That said, between you and me, they do not use words like "horse" or "dog" or "buffalo" to refer to animals that play a similar role in their planetary ecosystems, because that's just too prosaic for my taste. So, I've mostly used words created by Edgar Rice Burroughs in his two great (and public domain) planetary romance series. These include the following:

• banth - any large, four-legged predatory creature, superficially similar to lions or tigers in many respects except usually larger
• basto - a cattle or buffalo like creature, used for leather, fur, milk and meat
• calot - any more modestly sized pack hunting creatures in the ecological role of a wolf or hyena. Also used for domestic "dogs"
• kazar - an unusual form, known for its powerful short somewhat parrot-like beak. They usually are about sheep-sized and omnivorous, like a woolly Protoceratops and sometimes are domesticated for their wool, but on other worlds are only wild animals. On some worlds they've even developed lean, obligate carnivorous forms.
• mistal - one of two basic forms that serve as small domesticated animals. This one tends to be furry and "cute" but will root out and eat small pests. In other words, a space cat.
• rotik - known as "sea serpents" but in reality show a remarkable diversity of form. They are all, however, very large aquatic animals, and in very few cases is there any domestication of them.
• sorak - another small domesticated animal, although this one tends to focus more on the scales than the fur, and is somewhat less "cute." Still, soraks and mistals serve similar purposes. It's not clear why the ancients developed two templates for a similar function.
• targo - a variety of creatures that are known for their many eyes as a defining feature. They can range from the size of a rat to the size of a wolf. In addition to their spider-like eyes, they do, as it happens, produce a silk-like thread, which is sometimes harvested in domesticated versions of this animal, but they are dangerous for the unwary to keep, and when gone feral, they quickly turn predatory and dangerous.
• tharban - an often striped, solitary hunter. Not as large as the banths, but usually larger than calots, and only infrequently have they been successfully domesticated. Its theorized that they were developed, like the banths, for ecosystem control and to keep grazers like baso or kazars from over-running ecosystems due to lack of predation.
• thoat - a very wide variety of beast of burden. Some are similar to the basto, but they have less of a "cattle" like vibe, and more of a "horse"like vibe. That doesn't mean that they play the role of horses exactly; they can be as large and un-horselike as a dewback on one extreme. Sometimes, even two-legged animals that are similarly used as riding beasts of burden are called two-legged thoats, but that usage is not universal
• ulsio - a creature who's original purpose is unknown, but which has become a pest across many worlds, possibly as a result of an "inevitable" mutation that drives reptomammals to produce something like this in many worlds regardless of the designs of the original terraformers. Like a rat, these omnivores get into crops, eat carrion, threaten small children, and generally make a pest of themselves. Mistals and soraks are somewhat effective at controlling the population of smaller ones, but on some worlds they have become large enough to be immune to predation by those animals. Occasionally domesticated calots will deal with them in that case.
• vere - a "land crocodile" or rauisuchid-like animal. Or perhaps comparable to Megalania. Another hunting alternative to the calots, tharbans and banths. 
• zitidar - large, elephant-sized creatures. Sometimes domesticated, sometimes wild. Because of their large size, when fully grown they are immune to predation by all but the very largest and fiercest of banths.
• zorat - another modest-sized beast of burden. A "space donkey". Not generally capable of being ridden long distances, but on worlds where beasts of burden still get used for these kinds of things, they often are parts of caravans, carrying loads across the countryside.