On the Refugial Peninsula, Serina’s last lingering herds of land animals continue to cling on to a precarious existence on the very edge of Serinarcta, a continent quickly approaching total glaciation. Gone are serezelles and boomsingers, antlears and most other circuagodonts except the unusual scorplear. A few trunkos persist here - smart and hardy descendants of the snow snoot, the mammoth and the wump, the snifflers and two species of carnackles - but the dominant herbivores and the keystone species are the thorngrazers. Though these molodonts are some of the least intelligent land animals extant, with very small brains not only by Serinan standards but even when compared to Earth mammals - and lack many of the complex behaviors that their competitors use to survive, they find success through sheer size, belligerent temperament, strong physical defenses, and the ability to eat virtually everything. For what they lack in intellect or social graces they are certain to make up for in sheer bizarreness. The biggest of all the living tripods on land, thorngrazers of the ice age have skin embedded with additional misplaced teeth, three separate stomachs, and hollow resonating chambers in their snouts that amplify almost musical calls. There are no other tribbetheres like them, and the roles they fill have no direct counterpart on Earth - for though they are primarily specialized plant-eaters of the most rough and non-nutritious foods imaginable, they can in fact subsist on nearly any diet, including one of all meat, and for short periods can subsist even upon the organic matter in literal dirt.
Thorngrazers evolved in the early Ultimocene, from small terrestrial molodonts most closely related to seedsnatchers. They evolved from seed-eaters into foliovores as they left the trees, and the first forms were large, generalized grazers with heavyset builds known as omniphages. Unlike circuagodonts which went down the same evolutionary route to the grasslands but became fast and nimble and evolved a narrow clipping tooth arrangement, the omniphages stayed robust and kept the wide crushing teeth of their ancestors and evolved huge smashing jaws. With their two giant teeth - which, like all molodonts, are each structurally many smaller teeth fused together like the jaws of a stingray - these creatures pulverized each bite of plant matter thoroughly before ingesting, able to break down leaves, wood, sticks, and anything else they incidentally consumed in the process. Their gigantic mashing jaws were well-suited to feed on armored desert sunflower tree species, which sufficiently protected themselves from the feeding of birds with large thorns, and the common ancestor of modern thorngrazers was a desert-dweller. To protect sensitive tissues from damage while feeding the thorngrazers evolved spiny keratinous structures along their inner jaws and throats, but also rows of additional teeth independent of the fused grinding teeth, which radiated out their lips and gradually up and over their faces and even along their eyelids. Most of these supernumerary teeth were embedded loosely in their thick skin, rather than into their skulls, as they served a purely defensive function and no use in actually processing food.
As the climate cooled in the mid-Ultimocene, thorngrazers found themselves ingrained as a major component of a new ecosystem, the cactaiga. The descendents of the hardy desert plants they fed on thrived in a cooler, drier climate and spread out in sprawling bramble thickets, choking out other plant life in all but the dampest regions. Thorngrazers were the only herbivores suited to control them, and in their browsing opened them up and allowed other plants and animals to find room to grow. Colder temperatures resulted in thicker fur coats, and some of the small skin-embedded teeth on their faces grew deeper and rooted to the underlying bone, becoming large and intimidating horns (though on account of their origin, they would technically be classified as tusks.) Beneath their hairy exteriors thorngrazers continued to multiply their bizarre external teeth, which spread down the lengths of their bodies as small osteoderm-like balls of dentine firmly embedded in their hides that provided additional defense against the bites of predators.
Though cactaiga plants form the bulk of thorngrazer diets, they also feed on anything else they could including fruit, other animals’ waste, dead animals including old dry bones, and even live animals that don’t get out of their way fast enough. Thorngrazers, despite lacking specific predatory adaptations, will readily hunt young, sick or infirm prey, simply crushing them in their blunt jaws until they are turned to a pulp, and are in fact the most common predator of sealump chicks on the Serinarctan coast.
To digest such a wide variety of completely different food sources efficiently, the stomachs of modern thorngrazers are multi-chambered and incredibly complex, and have evolved their own bypass so that food which requires less digestion does not linger with food that takes a long time to break down and potentially rot. Their stomach has split, somewhat like a ruminant's, and now become three independent stomachs, with the first being the original one - small and generalized but very acidic - and the latter two descended from it becoming pinched off in two points and specialized for different needs. Smooth muscle valves separate both the hind-stomachs from stomach #1, and after initial digestion of all food the animal has taken in, the partially-processed food is then filtered into whichever of the other two stomachs is necessary. Meat and bone shards digests quickly in the first stomach and so is nearly liquified by the time the stomach dumps, so it filters through the narrower valve into a long and narrow stomach, less acidic, which is called the bypass or stomach #3, as food going down this route skips the stomach #2 entirely. Here additional enzymatic digestion occurs.
Wood and plant material is left almost totally undigested in the first stomach, and so clumps into fibrous masses. Too large to be filtered down the bypass and needing much more time to break down, they are taken up into stomach #2, which is effectively a huge fermenting bag that has evolved as a pouch off the side of the first stomach. This chunky mixture is pulled in here through muscular contractions after most of the fluids drain away through the bypass. Here they digest via fermentation for a much longer time, as much as forty hours. Unique among all vertebrates, this stomach also produces the enzyme cellulase, the genetic code to produce this having been acquired several million years ago through horizontal gene transfer from a now-extinct symbiotic stomach bacteria. This novel gene allows thorngrazers to digest cellulose from woody plants directly, get rid of the symbiont, and so hold on to the maximum amount of calories from their diet as possible. When at last all usable nutrition is obtained from even the most scarcely edible plant materials, this stomach empties through another valve directly into the intestine where all resulting nutriment is absorbed. Because stomachs #2 and #3 function independently, thorngrazers are unique among any animals in being well-suited to both strictly herbivorous and entirely carnivorous diets, but excel for being able to alternate and make use of the extremes of both that even specialized herbivores and strict carnivores often avoid.
Despite their wide array of adaptations that leave them nearly perfectly adapted to survive the ice age’s rigors, thorngrazers are notable for never being a very specious clade. Because they are so adaptable of diet and very wide-ranging as nomadic herd animals, they don’t readily split into separate populations focused on any one food source or habitat preference but instead form widespread populations of single species. There are thus only two living species now, and yet between them, they both live over the entirety of Serinarcta’s unfrozen land, in every sort of habitat from dry steppe to bog to the sea coast.