Dogbeasts of the Ultimocene

Canitheres: Dogbeasts of the Ultimocene

We begin our overview of Ultimocene tribbetheres with the most morphologically underived clade: the canitheres, which are sometimes also known - by the literal translation of their scientific name - as dogbeasts. While canitheres as a clade also encompasses the mertribs and their own descendant forms, the merwals, for purposes of conciseness we will exclude them to their own chapter and treat the canitheres from this point forward as paraphyletic, referring only to the terrestrial representatives unless otherwise stated.

Canitheres have changed relatively little in 67 million years, when the first cursorial predator tribbetheres evolved in the immediate aftermath of the Thermocene-Pangeacene boundary. This first form, ancestral to all other tribbetheres, were adapted with strong legs for pursuit hunting and jaws lined with sharp teeth to kill prey animals - traits still present in the modern canitheres, whose clade proper diverged from other tribbetheres about 60 million years ago. Modern canitheres however are distinct in a few respects from their earlier ancestors. Only two clades of terrestrial canithere has survived to the Ultimocene; the repandors, a group that has extremely specialized toward endurance running, and the barognatheres, now reduced to a single aberrant species.

Barognatheres

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Barognatheres, clade Barognatheria (heavy jawed beasts), once ruled this land. Dog-like canitheres of a primitive form, they were the first canitheres and diverged as a clade more than 60 million years ago. They spread across the face of the supercontinent in the Pangeacene, hunted serezelles and the first circuagodonts with strong crushing jaws and were, for a time, virtually cosmopolitan across Serina save for its islands. Yet their reign was short-lived, and their downfall demonstrates the principle of the competitive forces between clades that drives evolution. Predatory circuagodonts which evolved tens of millions of years later, from a more derived branch of tribbetheres with higher cognitive abilities, more developed social structures and jaws even better adapted for hunting megafauna, were a nail in their coffin. They began to move over the landmass within the past 20 million years, generally driving off and displacing the solitary canitheres wherever they met. Form and function that suited the barognatheres for tens of millions of years proved inadequate to compete with new, stronger and smarter rivals, and over twenty million years virtually this entire group of once seemingly indomitable predators dwindled, their lines of descent terminated anticlimactically, not from disaster but simple inefficiency. They were all, one by one, beat at their own game.

Except for one.

Today a single species of barognothere holds out in the deepest depths of Serinarcta's central tropical rainforests, an environment no other canithere has ever infiltrated. To survive for so long, it has had to substantially change away from its ancestral form and behavior - something few other canitheres managed. Once adapted to hunt on the open grasslands this once lanky hunter has grown squat and small of stature, only about twenty inches at the shoulder and three feet long, with short and stubby legs - a form of naturally inherited dwarfism that has proven beneficial at letting it run below the dense tangles of forest vegetation in pursuit of its prey. Its ears have shrunk as well, likely so that they do not snag, while its head is proportionally massive, supporting a huge jaw filled with sharp teeth. Known as the brushbounder, it is today the only canithere capable of - indeed, well adapted to - hunting and killing animals of its own size or larger: sometimes several times larger, as it is also the only species that has ever evolved to hunt in cohesive, cooperative packs.

Like their ancestors, brushbounders are endurance hunters, and one of the only such predators that is able to operate in dense vegetation, thereby circumventing its preys' natural desire to seek out cover and hide. Packs are usually formed of young relatives - only very rarely unrelated young adults that meet after leaving their mothers' packs at maturity - and consist of up to ten adults though usually just four or five. They hunt with highly efficient cooperation to bring down a wide variety of prey species, birds and tribbetheres alike. Smaller prey is driven by several individuals to a waiting ambush by the others, while larger prey are simply overwhelmed and brought to ground by the powerful clamping jaws, which have traded ancestral flexibility for brute strength. Blade-like teeth in the rear of the mouth slice together when feeding, allowing the animal to chew its food before swallowing.

The dark, spotted coat of the brushbounder blends effortlessly into the shaded forest floor where sunlight only hits the ground in small dappled patches, which allows these predators to stalk close to their prey before launching their pursuit, often catching it with little chase. When necessary, however, they may pursue their prey for as far as a mile through seemingly impenetrable undergrowth until it either is caught up in the branches, tires, or finds safety in a clearing where most creatures can then outrun the short-legged pursuer.

Short-legged and stocky, the brushbounder is the most basal living canithere, the last aberrant branch of a once worldwide, widely successful clade of strong-jawed megafaunal hunters since outcompeted by predator circuagodonts. Small herbivorous circuagodonts, meanwhile, are common prey (lower left.)

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Brushbounder packs are stable for life and are always segregated by sex, with males grouping together and females likewise. Males are larger, and as a rule their packs smaller, sometimes just consisting of bonded pairs. Females weigh about one third less than males but their packs are large, tending toward more than five animals, and as a result females are more aggressive at establishing and maintaining a dominance hierarchy which is formed initially on size and strength but is often stable for years even as lower ranking individuals may grow larger than the more dominant ones. Male and female packs do not share territories and are hostile toward one another outside of breeding, when the females reproductive cycles sync and they become restless and seek out a group of males to mate. All females in a pack will pair and may become pregnant at once, and in bountiful times the pack will cooperatively rear the entire litter, all of whom are usually related to some degree as their mothers are either siblings or cousins. If food is limited, though, the dominant female will kill and cannibalize pups down the line of dominance as they are born, beginning with those of the lowest ranking female and ending with the mother just below her, demonstrating an impressive cognitive ability to remember a very large number of individuals inherited social ranking. If conditions are unsuited to even a single litter, she will terminate even her own offspring if providing for them will threaten the health of the pack's adults, though this is very rare.

Generally, once pups are one to two weeks old and their eyes begin to open and they become more mobile around the den site, they are safe from infanticide. Open eyes in the young triggers stronger parental reflexes and appear to inhibit any culling behaviors. If all litters survive, the pack may raise upwards of fifteen pups at a time which remain fully dependent on their mothers for at least six months and rarely leave the natal group before ten. Eventually though all young do leave - brushbounder clans are almost never multi-generational, and young must leave to make room for the next year's broods. Sisters or cousins born and raised in a pack typically stay together for life while males split into smaller sub-groups; occasionally single young adults will be accepted into an unrelated group, and likewise old adults whose packs have died off may be accepted into groups of young, providing a sort of mentor role as experienced hunters.

The complex social structure which has gradually evolved in the brushbounder has gone hand and hand with increased intelligence, requiring selection for abilities like cooperation, problem solving and memory, and this species is very likely the smartest of all canitheres. Whether this, or their unusual form and habitat - or both - is the primary factor in their success versus the rest of their clade is uncertain. What is apparent is that this species has defied all the odds and remains a success story even in this rapidly changing world.

Repandors

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The repandors, clade Repandorsatheria, are the more derived and currently more specious canithere group on Serina, which comprise four genera. Their clade name (literally "upward-curving-backed beast") accounts for their extraordinarily flexible backs which curve dramatically during locomotion, serving as a spring to store and release energy and allow for rapid movement over land in pursuit of prey.

The painted repandor is the widest-spread canithere on land in the early Ultimocene. It is a grassland predator found across central Serinarcta. and preys primarily on the smallest of circuagodonts, known as smeerps.

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While repandors have specialized further toward high speed and so have considerably longer legs and leaner bodies than the first tribbetheres, they are the nonetheless fairly primitive. Indeed, the wider canithere clade [including its aquatic derivatives] is the only one among tribbetheria which has remained almost entirely carnivorous and the extant terrestrial representatives, despite their specializations, still retain the least divergent ancestral traits of all their clade. The extensible jaw typical of basal tribbetheres is present in all canitheres, but while the first species of the Pangeacene and their single modern representative had powerfully built crushing jaws and were capable of preying on relatively large animals, the modern repandors have moved away from this toward a precise snapping jaw well-suited to snatch up smaller vertebrate prey. This is a direct example of ecological niche partitioning which began to occur as a younger tribbethere clade - the circuagodonts - displaced both the stronger carnivorous canitheres which formerly hunted the flocks of serezelles and other placental birds, and much of these former prey species themselves, toward the end of the Pangeacene.

In addition to their more flexible spines, thinner build, and elongated limbs, the repandors are distinct from their predecessors in having evolved lengthier, narrower snapping jaws adapted to grasp, hold, and render into small portions whole vertebrate prey in a manner unique among land predators. When the jaw is closed and retracted this gives them an even more canine profile, with a long face like a collie, an impression furthered by the large, mobile ears which express emotion. As the jaws open up though the impression breaks down rapidly as the jaws expand first outward, then forward like a shark's, with the lower jaw in particular projecting down and ahead to grasp small fleeing prey and snap it against the needle-like fang teeth on the upper jaw. The bite force at the front of the jaws is not powerful, and though it holds the prey securely it rarely kills it outright. Instead, the final blow is delivered by the more powerful back of the mouth as the jaws retract back into place. While more basal canitheres could chew by shearing their rear molars together, the repandor uses this to kill. As the jaw retracts, the prey is pulled back into the mouth and between six razor-like slicing teeth in the rear of both jaws which then occlude together in a shearing motion, cutting the victim apart into several smaller portions that are then easily swallowed.

As a repandor bites, its jaws extend first outward, then forward in a grasping motion. As the jaws retract, blade teeth in the back of the mouth clip together to chew the prey into manageable morsels. This jaw extension is a hallmark of tribbetheres, which inherited it from their ancient fish ancestors.

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While predatory circuagodonts have replaced canitheres as top predators in their environments worldwide, the repandors have found a new place in the ecosystem. Today about fifteen species eke out a successful living as mesopredators, most of them primarily feeding on molodonts and small circuagodonts, Serina's ecological equivalents to field mice and hares, and to a lesser extent on the remaining small ground birds that are fewer now than at any time in Serina's history. Repandors are widespread across both major landmasses in the early Ultimocene, having diverged around the time the inland sea began rising to split the super-continent, and primarily dwell in open grasslands or savannahs with sparse intermittent woodlands where they have room to run down their prey in the open before it can find cover.

The typical repandor is relatively large - 3 to 4 feet at the shoulder - but very gracile, with a very lanky build and so is quite lightweight and delicate. Unable to fight larger carnivores, they rely on their superior agility to avoid confrontations. Though physically incapable of hunting prey close to or above their own weight class by limitations of their weak jaws, they do scavenge the carcasses killed by larger predators when the opportunity is available, rushing in, shearing a mouthful of meat and bolting away before the rightful owner can drive them off. There are a few small species, more in line with foxes than dogs, one of which dwells on the fringes of the southern desert and eats a diet high in insects (the chihuahua-sized foxtrotter.). Adapted to extremes of heat, the latter has the largest proportional ears of all canitheres, which it uses to cool itself.

Weighing only six pounds and barely knee-high, the little foxtrotter is a nocturnal desert specialist that feeds mainly upon insects. Large ears help to dissipate heat, while its wide eyes provide keen night vision. Its toes are long and covered with thick bristle-like hair, which simultaneously distributes their weight widely over loose sand so that they do not sink, and protects the paw pads from scorching ground temperatures.

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Some repandors have also specialized in more novel ways. Though it descends from a more typically gracile species which hunted small vertebrates, the myrmecophagous foxtrotter has evolved into an insect-eating specialist and now feeds primarily upon ants nests in the dry temperate regions. Though very closely related to the common foxtrotter and just a few million years divergent, this species has become quite distinct as a result of its unique niche. The jaws are elongated and weak, most of the teeth extremely small and vestigial, while the tongue is extremely long. Ants are not fast-moving prey and so this species is considerably bulkier than other repandors, adapted much less to high speed locomotion. Thick hair, adapted to insulate in cold desert nights, also furthers its impression as a larger animal than it really is. Its ears are much smaller than the common foxtrotter to reduce the tissue exposed both to ant bites and cold nights, and the first claw on the forearms has enlarged significantly into a powerful hook useful to crack open ants' nests, while the middle hind claw has elongated into a sharp cutting weapon used primarily for defense. It is bolder than most repandors, taking fight over flight when confronted as its large leg claws limit its speed even when threatened, and its markings are also highly distinct; bright black and yellow bands run down its back, making it obvious at a distance. This may serve as warning coloration, advertising both the aggressive defense it will mount if threatened and also the highly unpalatable taste of its acidic flesh, rendered very unpleasant by its almost exclusive diet of ants.

The mymecophagous foxtrotter, though very distinct in coloration, body shape and diet, is still close enough related to the common foxtrotter from which it may have evolved to interbreed; however as a result of its very different lifestyle this is very rare, and hybrids with intermediate morphology are poorly adapted to survive.

While their ancestors dabbled in social hunting 30 million years ago, mobbing large prey as a group to bring it down, the smaller prey size that all of the repandor species have since evolved to capture has made such social hunting with others of their kind largely unnecessary, for each kill is now often just enough for a single individual, and so these animals would likely be expected to be largely solitary and territorial. There is one situation where cooperation can bring benefits, however, and this is child-rearing; multiple adults can more easily provide for their young than a single mother, and the repandors are actually monogamous, pair-bonding animals. Thus, unexpectedly, these solitary hunters are actually social when off the clock. Pairs often mate for life, hunting separately by day (or, for some species, by night) but sharing a territory and returning to a common den site to rest. Allogrooming, where one partner cleans the other's skin or fur with the tongue and teeth, is a common gesture of affection and also serves to remove parasites from places one cannot groom easily on itself, such as the back and neck. Both parents cooperate equally to hunt and provide regurgitated food for the young, which are born in litters of two to six and stay in a secure burrow for about a month before leaving the nest, and with their parents for another few months before independence. To demonstrate his competence as a provider young males also often provide food to prospective mates as a courtship gesture, as well as to their bonded females while the mothers are brooding the young pups which cannot maintain their own body temperatures for at least two weeks after birth. As in all tribbetheres, food is transferred from parent to offspring, or partner to mate by locking their lips, after which the receiver produces a suction to pull pre-chewed food out of the provider's mouth.