The Flabbelops

Metamorph birds, widespread and more diverse than any vertebrate clade before them, have conquered land, air, and sea. Ranging from relatively normal-looking birds such as archangels to diminutive, insect-like ostepulmas which breathe through their spines, and the intriguing butterbirds with only a single jaw, some of the weirdest yet to be seen live underwater.

Aquatic metamorph birds have origins as far back as the early Pangeacene, when the small and underdeveloped young of the early changelings, which breathed through their thin skin, moved into increasingly damp environments in search of food and began to grow up in freshwater ponds. The larvae of later forms developed increasingly streamlined body shapes well-suited to swim in water. Shaped by the same selective pressures, they became fish-like, tail-propelled swimmers. Filling a completely different niche in the ecosystem from the adult, such larvae would eventually pupate and develop their adult traits, growing feathered wings, well-developed beaks, and taking flight. Modern examples of this grade of evolution include the shadowskimmer.

Some of these birds, through mutations that let their gametes mature without developing other adult condition, stopped maturing into a winged adult and stayed aquatic throughout life. An example of neoteny, changelings of this grade include sharkbirds - which still develop an adult-like cranial anatomy at adulthood, including a beak, and so still have some avian resemblance yet never leave the water and exhibit a fish-like body shape throughout life.

Virtually all fully-aquatic metamorph birds alive today, sharkbirds included, are eargills, a group which have evolved a gill chamber in their skulls in which water is passed through the mouth or the nostrils and through and out the ear openings. This is more efficient than absorbing oxygen through the mouth tissues alone, as occurs in the larvae of the shadowskimmer and other more primitive species, and allowed eargills to grow much larger. But there has been a trade-off - the ear drum is now gone and so these birds are deaf in air, though sensitive to water vibrations. Only a very small number of eargills retained adult flying conditions, such as those exhibited by efts, a group abundant in the early Ultimocene, as the lack of hearing would be a major handicap for any species with a lifespan longer than a few days.

Many eargills closely resemble lobe-finned fishes, with the forearms reduced to small fins and movement propelled by a muscular tail which is cartilage-supported and devoid of ossified elements. So close can the resemblance be, particularly with small baitfish-niche eargilled birds, that even sophont species such as the daydreamer and gravedigger do not distinguish them from ray-finned fishes. But some eargills are very distinctive, having adapted themselves to shapes and behaviors without piscine counterparts. Such is the case for the flabbelops, one of Serina’s weirdest ever birds.

The flabbelops begins its life typically - by eargill standards. A small egg, released into the current, hatches into a tiny, transparent larvae and feeds on zooplankton. Its forelimbs support each a long bristle-like feeler, which helps it locate small food items. It grows for several months until it is about six inches long and eel-like, but then begins to undergo a change of behavior. As it becomes too large to hide easily in surface vegetation it descends to the sea floor and there begins to create for itself a burrow in the sand. For a time, it emerges from its tunnel daily to hunt for small prey in the water, but as it matures - digging out its home around itself all the while - it spends more time within it until as an adult it is almost sessile, reluctant to ever leave it. Its jaws change over from a pincer-like structure good for snapping up active prey to a widely-gaped set of brushes, lined with hair-like cillia. As an adult, the flabbelops is a filter-feeder, spending the night weaving in the current with only its tail in its tunnel as it strains the current for plankton with slow flicks of its jaws. Huge, wide eyes stare in all directions around it - up, down, and around - scanning for potential danger, and if it spots a potential threat it slides quickly downward into its tunnel, covers itself with sand, and vanishes in seconds. By day as well it retreats - all 25+ feet of its body length - under the sand and there hides and rests.

Effectively solitary, but widely dispersed, flabbelops must gather at a common meeting place all at one time to spawn and do so by cues of the tides. When Serina is at the point in its orbit where tidal pulls are strongest on certain nights, the flabbelops leave their burrows and gather in fast-flowing open water to mate - the only time, as adults, that they will do so. Eel-like and sinous they swim and swarm together, twisting their serpentine forms together and releasing their sperm and eggs freely into the current; with luck, a few will eventually live long enough to mate in some ten years.

Within an hour spawning is complete, and the adults go back their own ways. They return to their holes, safe and secure… until the next time nature calls.