Ornimorphs

The evolution of a multi-staged life cycle in the changeling birds was a groundbreaking step in the evolutionary history of birds on Serina, allowing the group to radiate wildly into strange and wonderful forms unlike anything before them - and surely one of the most positively fantastical are a subset of them known as ornimorphs, which exhibit some of the most extreme developmental change of any animal ever to live.

above: though this image may appear to show the evolution of a bird-like creature from fish, amphibian, and reptile ancestors, it in fact represents the growth of an individual ornimorph bird over no more than four years of development through aquatic larval, terrestrial juvenile, and flying adult life stages.

~~~

Ornimorphs, in their larval life stage, are fundamentally similar to the ancestor of their neotenized, fully aquatic kin. They diverged early from the first changelings whose young were fully aquatic and like them still begin life as a tiny gelatinous egg deposited in a clump on water vegetation in a flowing stream by a flying adult and soon hatch into a creature that for all intents and purposes resembles a tadpole, which propels itself with a webbed tail and a pair of stumpy limb buds on either side of its head, which will eventually becomes its forearms. It lacks a beak, or a movable jaw at all, and feeds by scraping algae with a rasping set of downward-projected lips, and is entirely boneless, with only a cartilaginous rod where its backbone will one day be. They lack gills or lungs and use their entire skin to absorb oxygen from the water. About the only adult attribute it exhibits at this stage are its well-formed eyes, allowing it to find food and avoid predators even when newly-born.

Whereas some of the ornimorphs went down the evolutionary path of furthering their adaptation to life in the underwater realm and became the efts and, further derived, the fish changelings that no longer metamorphosize at all, for most representatives this is only a small part of their life cycle, and the ornimorphs are no exception. After a few months, rarely up to a year, the avian tadpole begins to change. More primitive changeling birds, including the basalmost aquatic species, transform from their larval state directly to their adult flying form in a matter of weeks while secluded in a cocoon of mucous. Like the ancestor of the ornkeys and archangels, however, ornimorphs have instead adapted to mature more gradually due to the extreme disparity between the biology of their larval an adult life stages, and remain active and alert while doing so over a longer time period. As a result, they can grow larger than their primitive kin and in doing so exploit a greater variety of niches and food sources.

Restricted by its lack of gills to a size of just a few inches, if a young tadpole-like ornimorph larvae wants to grow any larger to take advantage of other food sources or less oxygenated environments, it needs a more efficient respiratory system. It does not develop a gill from its ear canal, as the efts and changeling-fishes do, for it will need its hearing later in life. Instead, its lungs mature, allowing the tadpole to gulp air directly from the surface and thus expand its habitat out of the flowing streams and into slower-moving or stagnant ponds and pools... as well as onto land, to move between water sources. Once its lungs are developed and the larvae is able to obtain plentiful oxygen, it is able to grow larger. Its stumpy little arms become more prominent and small buds appear on the wrist, which soon extend into little frog-like fingers that let the tadpole crawl on its belly onto the shore. Here it finds additional food in the form of small invertebrates, and its jaws ossify and pull the mouth forward so that it no longer feeds on the bottom but can actively lunge forward and take small prey in the mouth, which it swallows whole. It becomes a small-scale predator, ambushing insects along the water's edge and chasing after the less alert ones, its forelimbs becoming longer and projecting to the sides of its body while small hind-limbs also emerge so that soon it has become a sprawling quadruped - superficially, an avian salamander. As its skin is no longer needed to absorb oxygen, it becomes thicker and drier, less permeable and more protective, and the "salamander" can soon extend its forays further inland, spending less and less time near the water it once depended on until it gradually abandons the shore altogether and moves into the damp undergrowth of the surrounding woodlands. The webbing on its tail recedes and shortly after the tail itself begins to be reabsorbed into the body so that it is only about half of its former length. The legs, front and back, are now long and semi-erect, each foot showing fully-developed toes tipped in small curved claws, and a horny sheath has emerged at the tip of the jaw which will expand over the coming months into a horny beak. Now between six and eighteen months of age, however, its transformation slows.

This will be a longer stage in the life cycle of many species, lasting up to two years, during which the ornimorph lives an active life as a small lizard-like predator. At first it cannot maintain its own body temperature, and relies on the environmental conditions around it to stay warm or cool down, but its highly efficient dual-flow respiratory system - which it inherits from its varied and diverse avian ancestors - still allow it a considerable endurance when the environment is warm and give it an advantage over cold-blooded insect prey. As the weeks go on, however, subtle changes are still modifying the juvenile's body. Its metabolism is slowly increasing, and it becomes less reliant on external conditions to maintain a steady body temperature, able to generate and maintain a level of body heat internally, and it extends its activity patterns accordingly, now hunting even on cool rainy days and after sunset when its prey are caught unawares. Its legs become longer still, its toes slender and grasping, and as it becomes more agile and approaches the end of its second year, it begins to expand its horizons upward into the forest trees. Clambering and leaping up the branches, a thin patagium of loose skin develops between its body and the joints of its fore and hind legs that allow it to glide between branches in pursuit of new prey - small birds and large flying insects - which it captures with a grasping motion of the powerful, weight-bearing arms that will soon become its flight stroke. As its leaps become longer and better controlled, small, sparse quills begin to emerge in tracts from the skin on its head and torso, while its limbs remain bare. It enters into a second growth spurt and over several weeks they open into a dense coat of insulating downy plumage which traps their owner's body heat, keeping its body not simply a few degrees warmer than its surroundings but maintaining a steady temperature around one hundred degrees, comparable now with the adults of other small birds. The "lizard" has transitioned into a Scleromochlus-like animal (and now also somewhat resembles an ornkey, though the to groups have reached such a form through independent though convergent means). Though it does not yet closely resemble a bird, per say - at least a typical one - it does have an acute resemblance to the distant ancestor which may have given rise to one, and has in any case completed its transition to a full-fledged endotherm by this time. Its development slows again, but only briefly.

In another few months its downy coat is broken through by a second, less dense layer of quills which emerge into an overlaying layer of barbed feathers. Especially long quills also begin to sprout in a tract along the outer edge of the arms and on the trailing edge of the fingers, unfurling collectively into a long, narrow wing formed from the elbow down by flight feathers and from the elbow up by a membrane of feathered skin. It is now that the creature rapidly develops its avian appearance, albeit one also intermixed with a distinctly pterosaurian influence as a result of the quadrupedal gait and partially membrane-based wing structure. As the quills along the arm elongate and begin to unfurl, their owner's leaps, glides, and grasps transform suddenly into powered flight, which is weak and fluttering at first but soon becomes strong and enduring as the plumage matures. When the animal is between 2.5 and 4 years old, depending on species, the process is normally complete and the nearly mature ornimorph leaves the canopy. From here on, its life will never be the same. Some transition entirely to a diet of airborne prey, ranging from small insects to birds, that it swoops after in the open air and catches in a wide gaping jaw edged in bristles that serve to extend its gape even further; others, longer of bill, fly instinctively toward the coast and from then on find their food by skimming over the waves like an albatross. Whatever they prey upon, however, all will be tied together by the fact that as adults none of them will ever intentionally touch the ground again in life.

Though a fleging ornimorph may land to roost for several weeks, eventually these rests become fewer and further between until eventually they will stop altogether. An adult, once it has found its grace in the skies, may never land again. Within a few weeks of its maiden flight, the claws on all but the third finger on the wings drop off, no longer of any use, while those on the hind legs are retained but may never again be used - some species, particularly pelagic ones, will now continue growing for several years more before sexual maturity and during this time greatly increase their proportions everywhere except the hind legs, which become stunted, tiny, and uselessly hidden in the plumage (if the adult ever did make a crash landing, the forearms alone would now be much more effective to carry it on the ground and more than sufficient to push it back into the air.) On Earth even the most airborne of all birds - swifts, swallows, and other highly specialized insect-eaters along with some seabirds - must return to the ground at least to rear their young, though they may spend the rest of their time (months, even) in the air. Ornimorphs, lacking either a hard-shelled egg to incubate or offspring that require their attention, are free of such constraints. They eat, sleep, and mate in the sky, with the females coming down only for a matter of seconds to skim the surface of a freshwater stream and deposit a mass of eggs, which will in turn repeat the cycle. This is the final stage of the ornimorph's life, the flying reproductive stage, and it is the longest by far - some species fly the skies without ever touching ground for more than one hundred years. Once fledged, it will not be until they are brought forcefully downwards in death that many will ever touch ground again.

Ornimorphs are not the only organism in existence which re-orchestrate their evolutionary history in their individual growth and development. Many creatures do so to a less extreme extent, including other birds as well as mammals, which exhibit piscine traits such as the beginnings of gills in their early embryonic development. Frogs and other amphibians do so to a more dramatic extent, demonstrating the transition from fish to tetrapod over the course of a few weeks to months. But it is only in the ornimorphs that a life cycle has been stretched out and exaggerated so spectacularly over so many stages, from an extremely primitive beginning as jawless, spineless fish-like creatures rasping at algae in the water to an ending as a majestic, warm-blooded bird that soars the heavens.

Few other creatures on Serina, avian or otherwise, are as splendidly strange as the ornimorphs.