Thorngrazers and Sawjaws

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.

The larger of the two extant thorngrazers is a bison-like animal known as the nimicorn, which is the direct descendant of the crab-headed thorngrazer. Though it is not the biggest ever land tribbethere (the armox and some of the earliest omniphages are contenders for this title), at around 800 lbs and up to five feet at the shoulder, this animal is no small fry itself. Nimicorns have dozens of horn-like tusks, with an average of six to ten being more than 12 inches long, though the number of tusks and their size varies widely. In some individuals the largest pairs may exceed 25 inches in length and are formidable weapons, shared by both sexes and used against predators. Like all thorngrazers the nimicorn is a social herd-dweller and protects its offspring in the middle of the group so that all predators that threaten them must contend with a wall of horns and hide, yet the social bonds between any two individuals are extremely weak, and individuals may move between groups freely and regularly. Thorngrazers communicate with loud bugle-like calls amplified by a hollow pocket of bone in their upper jaws, and within a given group the females are always socially dominant, with males guarding the perimeter and fighting over mating rights with one another. Due to their position on the margins males are disproportionately the ones killed by predators, but this benefits the population as a whole by preserving the females and young which are more important reproductively.

Nimicorns are best-suited as mid-level browsers of cactaiga and are the more primitive living species. But they are also the more predatory of the two, better able to run down live prey due to their longer legs. The nimicorn’s toes are splayed and its nails very large and becoming hoof-like, adaptations to simultaneously spread out their weight on wet soggy land or on snow and to gain traction on ice.

The other thorngrazer of the late ocean age is more derived than its relative and diverged a few million years earlier from the sextacorn thorngrazer. A smaller animal averaging 600-700 lbs, the razorback is now a short-legged and comical looking animal which feeds low to the ground, most often on grass, moss and refuse that they scoop up from the ground, roots and all, with a longer lower jaw and then chew up with the upper tooth plate. The razorback is so named for its especially dramatic osteoderms, literal teeth that have extended far down from its face to the heel of its hind leg and which form sharp blades jutting out along the sides of its gut. The entire hide of this species is beaded with small dentine nodules or toothy spines that make it almost impossible to bite into and kill unless it is flipped onto its back - and this is made difficult by its very short limbs. When danger lurks the razorback clumps up in its herd and lays down on the ground, tightly together, forming an armed fortress. Striking black and white banded coloration blurs together, forming a visually confusing mass that makes it hard to identify an individual and also gives the impression of having even more white spikes on their bodies than they actually do.

The calls of razorbacks are simple grunts, as the amplifying chamber is small in this species, and they are sexually-dimorphic, with males producing deeper belows. The appearance of this species is also so, with the six forward-facing tusks always longer in males as they are used to joust with one another. Both sexes have equally long jaw tusks, used to swing sideways and impale predators.

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Razorbacks and nimicorns often live in the same places, with their different stature meaning most of the time they feed at different levels, though both will compete over access to carrion. Occasionally nimicorns will hunt the young of razorbacks, which take several weeks to begin developing their body armor, but likewise razorbacks can kill young nimicorns simply by bullying their way into the herd and biting them to death, with their low height and heavy armor making them difficult to stop. Interactions between thorngrazers even within a single species are often rough and hostile, and along with such animals as the scorplear suggest a new evolutionary trend of survival not of the smartest, but of the toughest.

Despite living in large groups, thorngrazers are not altruistic. Females only care for their own offspring, and adults do not groom each other or look out for one another, rather all interactions are ultimately-self-serving - they are social only because it reduces the risk of any one individual being killed. Because they cannot clean themselves very well due to their inflexible necks, they are often rife with parasites ranging from small insects, squicks, and even nightbiters. Such pests, individually small but collectively deadly, are their most pressing enemies, for it is heavy parasite loads that are most likely to eventually weaken the sick and the old and cause them to fall behind where they will be finished off by their only large predators, the sawjaws.

Sawjaws are a new group of predatory molodonts descended from the hugger, a small cutthroat. Cutthroats in general descended from chiselers, a group of small arboreal animals that used their sharp teeth to cut into bark to find insect larvae, and when their ancestors returned to the ground when forests became rare they inherited a unique anatomy from their climbing ancestors. While other terrestrial tribbetheres have a running gait powered by pushes from the hind leg and a flexible spine that stores energy when bounding, cutthroats’ time in the trees hypertrophied their forearm muscles while greatly reducing those in their hind leg. Effectively they switched from rear-wheel to front-wheel drive, and from pushing to pulling. With the hind leg not playing a major part in running any longer, sawjaws have stopped using it. Running on their arms alone, they have become bipedal, balancing their center of gravity at the shoulders with a longer neck and a shortened abdomen. The hind leg, small and weak, is now used only for grooming.

Sawjaws, now much larger than huggers, are still twitchy, fast-moving animals that behave as if they were much smaller than they are. Their ears flex and rotate nervously, sensing noises, as if still fearful of predators they no longer have. They have become large carnivores from small ones on a rapid timescale, and it sometimes seems as if they have not yet fully adapted their behavior to their new circumstances. But now they are some of the most formidable hunters left on land, and have become specialist thorngrazer hunters.

Though their newly bipedal gait is less fast than circuagodogs’ they are much more powerful and far better suited to hunt such dangerous quarry. While circuagodogs evolved as pursuit hunters of fast and lightweight circuagodonts, and have suffered population declines in their absence as now they can only hunt trunkos (whose intelligence they struggle to outmatch), sawjaws use their strength to bring down their prey, which cannot run nearly as quickly as smaller tribbetheres due to their weight approaching the maximum possible to support with their leg arrangement. Jumping upon a thorngrazer's back using two hooked thumb claws on each wrist to hold onto prey, the sawjaws then reach down to slice under the throat with their bladed jaws which move in a forward-and-back sawing motion, rather than the stabbing one of the sabertooth circuagodog, and so resist breaking against the osteoderms in the thorngrazer’s skin. Though they are much smaller than the thorngrazer - about as big as a wolf - the sawjaws are much smarter, and also rely on cooperation to succeed and live in packs that work together to hunt, helping to take down food which is then shared by all. Thorngrazers are so numerous and so heavily afflicted with parasites, as well as injured males which have fought and lost for mating rights, that most of the time the packs need only to linger along the edges of the herds and wait for one to lag behind. Once they descend on it, its fellows - sensing its weakness - simply abandon it. For them, life is all about survival of the fittest. The weak get no consideration.

Sawjaws are ecologically wolf-like, and hunt like lions, yet their social behavior is unique to them. Rather than a single mating pair or a harem system, sawjaw packs are formed from several adults, usually multiple brothers that pair up with unrelated females, and all adults can reproduce and share parental duties with only a loose dominance hierarchy. This works for them as they produce only one or two offspring at a time rather than larger litters, and each offspring requires a prolonged childhood before they are independent. More like primates than wolves or big cats, sawjaw infants remain in total bodily contact with their mothers for the first two months by clinging to her belly or her back - a holdover from arboreal climbing ancestors - and so during this time mothers cannot hunt and rely on food shared by the rest of the pack. In stark contrast to many group-living species that rely on aggression and dominance to establish a pecking order, sawjaws - despite their threatening appearance - are remarkably peaceful. By sharing food with someone unable to hunt today, one is guaranteed a return of the favor in the future if they are injured or otherwise unable to hunt, so everyone gets to eat. In this way, they are very altruistic, and will even support injured or very old pack members that will never be able to hunt again. In doing so they still carry the torch as an example of the success of cooperative survival, even in the face of a rising, more aggressive ecology where fewer animals live this way.