Muridiungulates (Peragrattus) have existed for over 2 million years, originating as the descendants of Rattus migratorius that conquered the rat-grasslands by the time of the Middle Muricene. They altered their environment greatly, promoting the shift from the original prairie rat-grasses to rat-grains as the predominant group across their range. There were already a handful of species 1,000,000 Post-Abandonment, and further diversification has produced over twenty modern forms. This will be a look into a few of these and their places in Apterra's biosphere.
A notable feature of Muridiungulate evolution is that starting around 1.5 million PA, several lineages independently lost all use of their outer toes, with only two or three remaining as hooves. The most basal member, the Sappybara (P. tetradactylus) is the only surviving species without this feature. It lives in swampy environments all around the Medithalassic ocean, using its webbed, blunt-tipped toes to swim moderate distances. Its diet is generalistic; it is equally comforable browsing from pseudotrees, grazing in open areas, or collecting submerged vegetation, depending on what foods are available in its local area. When given the choice, though, it seeks out sweet woodlouse-grasses, especially the pond-grasses that grow beside the peaceful lakes where sappybaras raise their young.
Like the previous species, the Basketbuck (P. canistrequirus) is descended not from the Middle Muricene P. subabeliensis, but rather from a different basal Abelian lineage. In this habitat, where in many regions rat-grasslands aren't as dominant as they are in sub-Abeli, it pays not to be entirely dependent on Magnigranaceous food sources. The basketbuck's ancestors, therefore, broadened their horizons to include prairie-baskets and prairie-barrels that grow in low densities across rat-grasslands both then and now. With the expansion of more derived rat-grain-specialists into Panapterran ecosystems, basketbucks have now further evolved to feed almost exclusively on this alternative diet, a case of niche partitioning that has allowed them to stave off extinction but which required further adaptation on their part. A small body size was a necessity, as basket-grasses are too rare to support larger grazers. It was also advantageous to reduce their herd sizes for the same reason, but with ever-larger predators evolving, a completely solitary lifestyle would be suicide for such easy prey. As a sort of biological compromise, tight-knit groups of 3-5 are now the most common social structure seen in this species. Their three hooves are lightweight but broad to avoid making noise, though the inner and outer digits can be pulled backwards and off the ground when the animal needs to move quickly. Wide-roaming and never occurring in large numbers, basketbucks are not a keystone species, but nevertheless they've managed to carve out a place for themselves in a changing world.
All remaining species are the direct descendants of the sub-Abelian rattalopes of the previous age. Of these, none exemplifies the complete reversal of their ancestor's strategy better than the Grainzelle (P. granicarperus). This mid-sized rat now prefers the prairie rat-grasses shunned by its congenerics, taking advantage of a little-utilized resource. As prairie rat-grasses produce a smaller quantity of seeds than their rat-grain counterparts, Grainzelles also incorporate a modest quantity of grass leaves and stems in their daily food intake, a change that's only possible because prairie rat-grass foliage is slightly more nutritious than average for its family. This species was larger and more common in the past when its food source formed monocultures across Abeli, but now has become relegated to a minor component of today's herbivore communities. Like the basketbuck, it now must search far and wide for small patches of suitable food, shrinking in both average body size and overall population numbers over the millennia.
The rat-grain-eaters, on the other hand, are currently in their heyday. Specializing on a diet of juicy, nutritious rat-corn cobs is the Shuckertooth (P. decorticator). The upper incisors of this rattalope curve slightly backward and have a prominent gap between them, allowing them to simultaneously peel the husks and pop the individual kernels off the stem, quickly exposing the rich flesh of the cob below. This process is quick and efficient, and the shuckertooth can consume all the calories it needs for a whole day in under an hour. Its feeding strategy leaves the grains undamaged and scattered all around its feeding site, ensuring the next year's crop will be just as bountiful. With ample time left for leisure, shuckertooths can sleep up to 16 hours a day, guarded by sentinels that take turns vigilantly watching out for the dozens-strong herd at all hours. Being large enough to stand up to most predators if they work together, this species does not stampede; it prefers to hold its ground and form a protective circle around the young of the group.
A close cousin of the shuckertooth and making its living off smaller but more numerous rat-wheat seeds is the Millertooth (P. fortops), whose massive molars grind its tough, hard-shelled food to a pulp in a motion that passes it backward with each bite, allowing it to process a continuous flow of grains as it grazes. To increase leverage, its jaws are short, allowing powerful muscles to exert impressive pressure, a feature equally useful for fending off predators as it is when peacefully munching on a mouthful of rat-wheat. With its food being smaller, less nutritious, and more energy-intensive to consume than rat-corn, it has no choice but to devote nearly all its waking hours to the task of chewing it up. In return, though, it faces almost no competition; rat-wheat seeds have become so strong that no other rat can crack them. While this gives the appearance of a fierce arms race, it can also be understood as a sort of untrusting mutualism - millertooths drop up to 10% of the seeds they pluck from their parent plants, making them among the most effective dispersers for the rat-wheat, which has evolved its toughness to ensure only one species can access it.
Finally, the largest member of the genus is also the only one regularly found outside of rat-grassland habitats. The Rattalox (P. setosus) is, as its common name suggests, the largest rattalope - and indeed Apterra's current largest rat of all. Weighing in at just over 200 kilos, this shaggy-haired giant possesses three hooved toes to support its bulk, unlike its two-toed millertooth/shuckertooth sister clade. While it has a minor presence in Abelian and Loxodian prairies, the majority of its numbers can be found on the slopes of the two great Loxodian mountain ranges, where it thrives on the alpine tundra and even finds success in some taiga pseudoforest biomes. As the planet cools and its preferred environment spreads, rattaloxen have recently spread across the land bridge to what was once the Northern Isles, where they brave the coldest arctic temperatures the planet has to offer. A small population has even crossed through the Ailox region into northern Ailuropia, the first rattalope ever to do so. In addition to the warmth provided by its long coat of fur and increased body mass, the rattalox owes its success to its intestines. By increasing the length of its digestive tract and expanding its cecum, it ensures that food remains in its body longer, improving the efficiency of its hindgut fermentation. As a result, it eats what no other rattalope bothers with: the dry, crisp, non-flowering parts of rat-grasses that contain too few easily-accessible calories for any species besides this one to subsist on. These hardy survivors, though, squeeze every bit of energy they can get from their food, which also includes twigs, leafy greens, roots, and occasionally entire small pseudotrees that it can topple with a single, powerful shove. Unlike so many species that are in a state of decline as Apterra cools, the rattalox only grows more abundant as the ice age approaches, and it's set to be one of the best-prepared for life at the end of the Muricene.