The subfamily Capiodocinae (the descendants of the previous age's genus Capiodocus) is the least diverse of all swattermouse groups, containing "only" a hundred or so species. The earliest to branch off were the widely-distributed matkelp-dwellers, followed by a tribe of desert specialists who make up most of this clade's present members. The most derived tiptoe swattermice fall into the genus Panpurificator - the Great Cleaners. There are only two species in this group, but both can be found across all of Panapterra, with subspecies everywhere from deserts to rainforests to tundras. Together, they serve as the cleanup crew of the planet's burgeoning megafaunal community, suppressing a wide assortment of pests and pathogens that would otherwise overwhelm the landscape and its inhabitants.
The decaying remains of newly-evolved massive birds and mammals have become one of this age's greatest engines driving terrestrial biodiversity. Not only have thousands of small animals come out of the woodwork to take advantage of this food source (one that only becomes more abundant with each passing millennium), but one of them has been able to rapidly evolve a body size on the same order as the dead giants it feeds on. The Kleptocrat (P. cathartomys) is an 80-kilo, 1.5-meter-tall meat-eater with incisor teeth designed to process huge carcasses. The lower pair are flat and nearly vertical, allowing them to hook under the thick hide of a large animal and peel off strips of flesh. When the rat has dug deep enough to hit bone, it uses its gracile arms to slip through a gap and feel around inside. It then scoops out fistfuls of muscle, organs and connective tissue, hollowing out the body cavity without ever having to break bones to get inside. It typically eats over a quarter of its own weight in a sitting, as a period of good luck for the herd could mean the scavenger has to go weeks without eating.
Kleptocrat population density is strictly limited by the population density of large animals and the efficiency of their predators. For example, a herd containing 1,000 adult Muridiungulates with an average mass of 200 kilograms (of which 75% is flesh edible to kleptocrats) and a mature lifespan of ten years will yield at least 15 tons of meat per year. Kleptocrats have a high metabolism and spend most hours of the day searching for food, so each requires about two tons of meat per year. Thus, this herd would theoretically support seven or so individuals. In reality, two or three is more likely, as some meat is lost to decay and small animals, and an even larger portion is often taken by the predator that killed the herd-rat in the first place. Of course, kleptocrats can make up for these losses in other ways: individuals survive food shortages for a time by switching to a diet of small burrowing rodents or birds, by picking off the weakest members of the herd, or by forming temporary packs to bring down perfectly healthy animals whose death they'd normally prefer to passively await.
Ultimately, though, none of these are sustainable lifestyles for the kleptocrat. It isn't as effective at catching burrowing vertebrates as are slinksteppers, and it has a lower hunting success rate than more dedicated predators like terror kiwis, slashsteppers, and some grimbills. If any kleptocrat population relied on these strategies as anything more than supplemental or emergency measures, it would find itself outcompeted by these specialists, so the species has adapted to specialize just as strongly for its scavenging niche. The most important challenge in its day-to-day life is intimidating predators into abandoning their kills, and its solution is to fight well above its weight class in conflicts against its fellow meat-eaters. The innermost toenail on the hindfoot is extended into a strange-looking spur that does not touch the ground. It curls gently upward and just a bit inward, causing it to scrape against the claw on the other foot. This forces the spurs to self-sharpen, which, in addition to their roughly circular cross-section, makes them a deadly threat to any predator that tries to stand its ground, though pretty much useless against fleeing prey. Though a single kleptocrat can often steal a kill on its own, it knows it too will eventually be driven away without backup, so it tolerates conspecifics as long as there is enough meat to go around. This feast can last for several days, after which the group disperses and each cleaner does its best to catch back up with the herd.
The kleptocrat's closest relative differs from it in many ways. It is smaller, rarely more than 25 kilograms, and it moves on all fours unless it needs to run quickly or stand to search for danger. It has a bare, narrow snout filled with weak teeth that betray a diet containing nothing particularly difficult to physically process. At the same time, it shares its cousin's super-corrosive stomach acid and resistance to transmissible diseases. The two species share a migration pattern: they closely follow herds of megafauna and establish neither long-term territories nor long-term intraspecific bonds. Another immediately obvious difference is their numbers; while kleptocrats can only sustain a sparse existence, a Coprovore (P. coprovoris) diet can support a population many times larger. The same 1,000-strong herd generates two to three tons of feces per day, and each coprovore needs at most three kilos daily. Like carrion, dung is susceptible to being carried off by small arthropods and tetrapods, though at least there is no need to chase off larger competitors. On the other hand, if the herd defecates in, say, a river, its entourage of coprovores will simply have to go hungry that day.
Both species of great cleaners are shunned by the herds they track. In the kleptocrat's case, this is a preventative measure against opportunistic predation, but from coprovores the danger comes primarily in the form of diseases. Though immune to most pathogens excreted by its benefactors and nose-blind to its own stench, the copovore is perceived as a repugnant assault on the senses by nearly all the species around it. This, of course, does not bother the coprovore, which is more than satisfied in the company of its conspecifics and, in most cases, congenerics, since kleptocrats are equally germ-resistant and thus face no risk from hanging around their cousins. Predation and scavenging by kleptocrats on coprovores is vanishingly rare, as the two are still so closely related that the few illnesses they do face can be easily passed from one to the other. Instead, they work together to achieve their common goal of keeping close to the herd, even going as far as adopting each other's orphaned or abandoned young. This is often a temporary measure; kleptocrat mothers may leave their pups with a coprovore for up to 72 hours after locating a carcass, avoiding a situation where the young get caught up in a fight or stranded far from the herd. In exchange, the larger kleptocrats offer a share of their milk to baby coprovores during times of low food availability. To prevent freeloading on both sides, female kleptocrats and coprovores may form permanent alliances, a surprising trait given that neither engages in such behavior within its own species. Since the former is far less abundant than the latter, kleptocrats are in high demand among coprovores, some of whom go to such extremes as killing small game, which they use as gifts to win the favor of their larger cousins.
In many other species, adopted offspring tend to imprint on their surrogate parents, eventually seeking a mate among the species they were raised as. When the adoptee and surrogate species are closely related, the outcome is usually hybridization. However, hybrids in this genus tend to be at a disadvantage, being less capable of fighting for carrion and slower to arrive at dung piles. This has posed a selective pressure on both coprovores and kleptocrats to seek out mates within their own species, regardless of how they were raised. To this end, the two have distinctive markings on their arms and an instinct to breed only with individuals bearing matching ones. The bare-skinned and otherwise drab grey forearms of adult kleptocrats have a yellow stripe running from the inside of the elbow to the wrist, where it splits into individual lines running down the fingers. Coprovores, on the other hand, have alternating bands of white and black fur running the length of their arms (a bolder version of the grey-and-brown striped coloration of the neck, back, and tail), trailing off to hairless black skin from the upper wrist onward. In both species, courtship involves pairs repeatedly holding hands, lining up their arms side by side, and scrutinizing the patterns to a seemingly excessive degree to ensure they match.