Ornkeys of the Late Pangeacene: The Peraxils

240 million years PE, the ornkeys have given rise to a number of fascinating species, the serezelles most notable among them; even though many representatives of that branch have already died out, several particularly unique representatives, such as the spearrunner, still survive. One group of these placental birds which has not changed so drastically at a glance, but which has evolved a very novel feature used to rear their young and a complex social behavior, is the Peraxils, a group of ornkeys which care for and rear their young in pouches.

Unlike earlier ornkeys - but like serezelles to which they are closely related - Peraxils have evolved to care for their young in order to improve their survival in colder climates. Most species in this clade have moved north, out of the tropics, and now live in areas with cold winters. Chicks are still born at a featherless, undeveloped stage but unlike their ancestors, peraxils carry their young with them, protect them from the harsh climate, and even provide them with food. Pouches of skin beneath the arm, insulated by long hair, have evolved to provide a shelter for the neonates to grow.

One of the most socially advanced of the peraxils, as well as among the most beautiful, is the the whitecloak. This is a large species, up to thirty pounds and three feet tall, native to northern temperate forests on the northern continent. Long hair-like plumage insulates it from snowy winters. Males of this species are boldly marked in red, black and white; the cape of white feathers hanging down its back gives it its name. Females are grey all over. Whitecloaks are extremely skilled brachiators, with very long and flexible forearms that let them leap from tree to tree at breakneck speeds. The hind legs, though much shorter, are also still dexterous and well-adapted to perch. This species is secondarily bipedal when walking due to the length of its arms making quadrupedal locomotion cumbersome. They are omnivores, eating a wide variety of food. In summer they feed heavily on fruit and insects, while in winter they feed more on large seeds which they crack in their strong bills as well as on small vertebrates that they catch in their sharp talons - even flying birds can be swatted out of the air. Whatever they feed upon however, they find it in the trees; they only go to the ground in emergency situations, at which time they locomote with a bipedal hopping pattern.

Whitecloaks are highly social; males are territorial and will inflate a prominent white gular pouch and sing loud, booming songs which carry several miles across the woods to ward off rival groups. They lead groups of females and their young. Gripping the hair with their forearm claws, the hairless, pink young do not leave their mothers' pouch for several months, during which time they are fed regurgitated meals by their mother and so no longer forage on their own for food. When the young are fully feathered and able to maintain a warm body temperature, they begin to climb out and onto their mother's back, gradually gaining more independence but remaining with the family unit for protection and relying on what their family unit has learned about where to find food to survive, rather than relying strictly on instinct; whitecloaks demonstrate well the more primate-like evolutionary path some species of the peraxil clade have begun to go down. Moving into cooler climates has likely been the impetus for both increased sociality and parental care in the peraxils; the cold makes it harder to keep warm both as an adult and as a small, featherless juvenile. Prolonged parental care and social bonding allow the sharing of warmth and resources, making life a little easier.

In many ways, the mosset is the opposite of the whitecloak; it is solitary, it is very slow moving, and though it lives in equally temperate climates, it does not worry about keeping warm through winter - instead, it retains the ability to lower its metabolism back to a juvenile state and so hibernates in hollow trees when the mercury falls. Yet the mosset, too, is a member of the peraxil clade and raises its young in pouches beneath its arms. The parental care in the mosset is arguably even more developed, as she belongs to a clade within the peraxels that does not feed the chicks simply her regurgitated food. Instead, the female produces a nutritious crop milk from glands in the sides of her beak; this milk is uniquely derived from saliva, and likely evolved as the young would lick partly digested food from the mother's mouth, also ingesting some of her saliva. Over millions of years, the saliva produced became higher in fats and sugars and more nutritious until it was the primary source of nourishment for the young. Feeding her young on this special saliva milk the mosset's young grow much more quickly than if they were fed on leaves alone.

Mossets are not more primitive than whitecloaks; their seemingly less developed social behavior is a reversion rather than an ancestral condition, and the mosset actually evolved from a more social ancestor. Its slowed metabolism and loss of newly-evolved sociality has to do with its specialization of diet toward leaves exclusively, which take a lot of effort to digest at the expense of its brain and other body processes. Like a sloth, the mosset climbs primarily upside down, hanging by its hooked claws from branches, and feeds on foliage - mainly of sunflower trees. Interestingly, it has evolved a long hooked tongue to pull leaves into the mouth, rather than using its arm claws, which can no longer open or close from the hooked posture they are kept in to cling to branches. The mosset also has a large gular pouch like the whitecloak, but uses it as a fermenting chamber to digest its fibrous diet.

Mossets often live and feed in ant-symbiotic trees, but are not harassed by the insects as are most herbivores. Their extremely slow movements do not readily trigger defensive aggression, even as they remove and feed on the trees' leaves. If they are anyway threatened by approaching warrior ants, the mosset can fully freeze its movements for as long as two hours and blend into the scenery with their mossy green pelage, which is actually structurally brown; it takes on a green hue in summer as a result of symbiotic algal growth in the feather shafts. More remarkable however is its use of chemical crypsis, or hiding its scent, to avoid detection. The slow metabolic rate of this species has a side effect in reducing the metabolic production of odorants which give other animals their specific scents, and over millions of years of evolving to coexist in ant trees the mosset has evolved to produce almost no volatile odorants at all, making it virtually impossible to detect chemically - but it does not end there. In addition to producing no scents of its own, the mosset has evolved the ability to metabolically incorporate the chemicals that lend the trees upon which it feeds their own characteristic scents into its preen oil gland. As the mosset grooms itself, it effectively scents itself as the tree itself, to such an extent that the symbiote ants will work right over its feathers and clean it as if it were the tree itself. This trifold combination of behavioral and physiological adaptation renders the species virtually invisible both to potentially dangerous ants and also large predators which hunt either by scent or by smell.

The only time the mosset produces any odor is when it must defecate, which only occurs a few times per week. To do so, the animal flips itself right side up and shoots its waste projectile-like to the forest floor, taking great care to not soil itself or the tree it lives on.

Mossets specialize so highly to live on a single individual tree that this causes complications when mating. They are territorial and generally defend their own trees from any competitors, and so to mate must leave their tree and find a partner somewhere else. Were a mosset to leave one ant tree and climb into another, the out of place tree scent it carries in its can trigger an attack by that tree's defensive ants. It is thus safest for mossets to breed on the forest floor. Males call out to females with a shrill cry and wait for answers; when they get a response, they climb to the forest floor and crawl - slowly and in a cumbersome, splayed manner - to the source, where they will then meet the female at the base of her own tree. Mating is brief and the female then returns to her tree instantly while the male must crawl back to its own at some distance. This is the most dangerous time in a male's life, and a rather large percent of males are killed either before or shortly after mating.