Circuagodonts of the Early Ultimocene

Circuagodonts

Circuagodonts are a highly successful molodont clade that very early on switched to a grazing diet from a seed-eating one and which is still speciating today. From ancestors very much like the modern poppits has sprung a diverse assemblage of modern diversity. All circuagodonts are allied by their specialized jaw, with the upper tooth being wedge shaped, narrow and sharp at the front and blunt and grinding in the rear, along with a recumbent lower tooth that projects out of the mouth. By sliding the upper tooth forward, the jaws operate like a spring-loaded branch trimmer. When the tooth is pulled back, the grinding cusps on the back of it meet those deep in the lower jaw to chew the food. Circuagodonts are thus very efficient feeders of coarse plant material and evolved as grazers of especially silica-rich grass stems few other animals could eat. They experienced their first diversity boom with the rise of the fatally-sharp, armored razorgrass in the Pangeacene, which was itself worsened indirectly by other molodonts feeding heavily on tree seeds and reducing the extent of forests, but have since adapted to a very wide variety of diets with only fairly slight modifications to their jaw structure. Circuagodont jaws are multi-purpose cutting implements that have in different lineages specialized to cut grass, branches, and even flesh and bone. Among all molodonts, no other clade which diverged more recently shows such a wide variety of dietary variation.

A diagram of the jaws of a typical herbivore circuagodont.

All circuagodonts are also allied in being cursorial; indeed, they are the only molodonts that are adapted for prolonged, fast movement over land. Their legs are elongate and the toes reduced in number. Among all circuagodonts, it is only a few very large and armored forms that do not run well. We have already seen some circuagodonts of the early Ultimocene, notably the antlears - and so the evolutionary history of these forms will only receive brief attention here. This update will focus more highly on three unique modern species of still unseen life histories, each filling a distinct niche in the ecosystem; the smeerp, the armox, and the circuagodog.

Smeerps

Widespread across the grasslands and open woodlands of Serina in the early Ultimocene are many rather similar species of small and very primitive circuagodonts known as smeerps, which both superficially resemble, and fill the ecological roles of, rabbits. Never any bigger than a hare, they are highly important in the ecosystems they inhabit as the primary if not nearly exclusive prey of the repandors and the primary limiting factor in the growth of razorgrass which tends to dominate grassland ecologies to the exclusion of other pasture and detriment of other animal species when they are not present to graze it down. Smeerps are exclusively vegetarian and eat primarily silica-rich grasses and a small percentage of woody plants. Soft herbs, preferred by other grazers, are rarely eaten, and so smeerps help to ensure a biodiverse habitat with abundant food for many other herbivores.

Smeerps closely represent the form that the larger and more specialized circuagodonts evolved from and are morphologically intermediate between these clades and the non-circuagodont poppits, their nearest relatives. Like most circuagodonts they have seasonal fur coats that become thin in summer, revealing camouflaging greenish skin patterns, and insulating in winter with a brown or gray pelage to hide against deciduous trees. Unlike poppits, smeerps don't generally live underground but rather above it; their young are able to walk at birth and are generally hidden in thickets or tall grass, attended by their mother just a few times per day. This is in contrast to the larger circuagodonts whose young evolved to be highly precocial and run with their parent nearly from birth. The survival rate of the young is very low, with predators catching most, but compensated for with a high birth rate, up to six annual litters of up to four kits per year in mild climates. Though any circuagodont has a powerful cutting bite that they will use as a last resort against an enemy, smeerps' primary defense besides fecundity is flight. They are rapid runners that strive to confuse their pursuers by dodging and backtracking, as at a run straight out their predators can outrun them. Despite this, few if any smeerps live to old age.

Sociality in these animals is the least developed in circuagodonts. Female smeerps are social only with their offspring, and males not at all. Bucks fight fiercely for breeding rights and are even aggressive toward females, dominating them with a bite to the neck and a generally larger weight. Females do not resist, as this aggression demonstrates the strength and vigor that will be inherited to her offspring, traits that will increase their odds of survival.

Armox

The armox is the largest of all circuagodonts, and one of the largest tribbetheres on land after the omniphages; it weighs up to 1,200 lbs. A descendant of the antlears, this species - a native of the northern taiga - has traded the dexterity of its mobile spiked ears for strength. With enormously wide, heavily armored ears that both rotate at their base and fold halfway along their length, the armox's ears have evolved into defensive shields that can be swung quickly around to protect the neck of the killing bites of large predators, such as the predatory grappler birds, and swept forward over the face to protect the eyes and snout from the sharp, slicing bites of the carnivorous circuagodonts.

Today bulky and fairly slow runners, armox are most immediately descended from a much more gracile ancestor that adapted to run on only one primary toe per limb, with the other digits shrinking or being lost entirely. Though speed is no longer its defense, the armox retains a single large hoof on each foot, with a pair of smaller, mostly vestigial dewclaws on each leg behind it.

Armox are very social herd-dwellers, relying on the collective defense of many individuals to form a living wall around their more vulnerable young, who take many years to develop their antlers to their fullest extent. Few predators, even the largest, can break through such a barrier. The only negative of the enormity of their horns is that the armox has lost the original benefit they provided as grasping manipulators and must feed closer to ground level. Perhaps because of this, it is primarily a far-northern species, living where trees rarely grow past its head height anyway and so avoiding being relegated to feed only on the sparse undergrowth of the taller southern forests. Their jaws function like loppers, cutting large branches which the creature chews and consumes entirely, wood and all.

Circuagodogs

Carnivorous circuagodonts are the most divergent clade so far as dietary and tooth specialization, having become nearly obligate carnivores. Among them, the most feared are the wolf-like circuagodogs which live across Serina's more open habitats. To facilitate efficient predation, the lower tooth is now highly serrated and ends in an upward hook which is used to tear flesh from bone, while in the razortooth circuagodog, the upper tooth is razor-sharp and can be extended far forward to allow the predator a wide biting gape, then retracted to slice deep into the flesh. Prey is killed from many such small, bloody wounds to the face and extremities which are so deadly because the species is a persistent social pack hunter, which may follow large prey for days to wear it down until it can be eaten alive.

Razortooth circuagodogs are one of the few animal predators of boomsinger that can kill their prey outright, able to kill young individuals by cutting the tendons in their long legs. They also hunt terries - herbivorous softbilled birds - but primarily prey on their own relatives: the larger herbivorous circuagodonts such as the antlears. Armox evolved their defensive habits to defend themselves from circuagodog predation, to such an efficient extent that today they are largely beyond this predator's means.

A diagram of the jaws of the razortooth circuagodog. The upper and lower jaw can move independently, letting the mouth stay open while the upper tooth strikes up and down to slice the prey, then letting the hooked lower jaw tear the flesh for consumption.