Pachyderm Serestriders

The warming climate of the Thermocene has been very beneficial to the giant herbivorous canaries known as serestriders, which rely on warm environmental conditions to incubate their eggs in the soil. Formerly able to breed only in a narrow belt of tropics near Serina's equator, the warmer global climate of the last 25 million years has now allowed them to spread from pole to pole in Serina's western hemisphere. The group has diversified ecologically in this time, producing a variety of new species including horizontally-set grazers with elongated horse-like skulls, semi-aquatic species which feed on aquatic foliage, and an increasingly varied tapestry of long-necked browsers adapted to feeding on a wide variety of plant species. The mucks, small entirely featherless tree dwellers, are probably the strangest. But another of the most notable groups of the Thermocene are the pachyderm serestriders.

Pachyderm serestriders are so named because, like the mucks to which they are related, as mature adults they are effectively featherless, instead covered with a very thick hide akin to that of a rhinoceros, which is often additionally ornamented with large knobs, spikes, and scutes of keratin. Formed not from feathers or scales but from the epidermis itself, these horny structures perform a defensive function, making it difficult for large predators to get a grip. What makes members of this group stand out however is not simply the loss of their plumage, but rather the process through which it occurs. Unlike mucks, chicks of this lineage retain feathers and come out of the egg with a full coat of plumage - but no longer the typical fuzzy down of precocial birds. For the first several years of a pachyderm serestrider's life, until it grows large enough that the local gauntlet of small fast-running carnivores no longer pose a regular threat, the bird is actually covered in a dense pelt of stiff bristles and long barbed spines, which like the keratinized growth of the adult serve to make it an unsavory mouthful at best. The quills are long enough to reach past the armored beak of most avian carnivores and easily detach in the nostrils and near the eyes of potential predators, meaning that most small predators which might normally be inclined to grab an otherwise defenseless serestrider chick will typically give those of this group a wide berth.

above: three specimens of a single species of pachyderm serestrider - a large browser native to the tropical savannahs of South Anciska. From left to right: yearling chick still sporting a full coat of bristles; eight year old juvenile, beginning to develop horny armor over its body and having lost a majority of its spines except for along its back; adult male in breeding coloration (+15 years of age), almost completely without plumage save for some small bristles on its rump, neck, and face and now showing very pronounced body armor in the form of thick defensive plates and horny growths.

The adult male also demonstrates the large defensive hand claw carried by most serestriders as well as their basal kin, which can be folded out of sight into a fleshy sheathe in the wrist when not in use.

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Young pachyderm serestriders retain their plumage from anywhere from five to ten years. The process of feather loss is not instantaneous but rather occurs over several years time, as the animal is also putting on mass and gradually developing its adult armor. The switch between quills and epidermal armor also goes hand in hand with a shifts in metabolism and ecology; young individuals are active and lightly-built as well as omnivorous, consuming a wide variety of plant foods as well as invertebrates and small animals. They are long-legged and adapted to running and fleeing their predators at considerable speed, whereas adults are exclusive herbivores with long necks suited to browsing the treetops; they are also much more robust and much less inclined to move quickly to escape danger. By the time most of its spines have been shed and replaced by armor, the serestrider's metabolism will have slowed dramatically. It will no longer be able to warm its own body through endothermy but instead will make use of its own bulk to do so through the process of gigantothermy; an adult rivals an African elephant in weight at maturity and will continue to grow as much half again heavier in the years that follow - granted at a much slower rate - and in the tropical climates these animals inhabit this is sufficient to keep them active enough to fulfill their metabolic needs. An adult past the age of fifteen years is already large enough that few carnivores can bother it, and those which otherwise could will find it a very difficult meal to handle, for all the gentle giant must do is turn its back to a potential threat, revealing the armored surfaces which most of its enemies will find very difficult to get a grip on. To further guard themselves from danger, adults move in large herds which youngsters begin to associate with around the time they are five or six years old, just as their spines begin to shed; until then, they live a solitary life in the jungle undergrowth.

Adults are lethargic in comparison to juveniles but do retain the ability to actively defend themselves, even at full maturity when they prefer a more passive approach to warding off danger. All serestriders have large claws on their arms which can give any predator a nasty lashing, and even a fully-grown adult retains the ability to briefly balance on a single leg to kick out at a predator: the middle toe of both feet supports a particularly long claw which can disembowel anything that comes too close for comfort.