The Kingfin (Early Cryocene:50 Million Years PE)
The kingfin is a macropredatory birdwhale, adapted to eat mainly other birdwhales and the related bloons. With viciously hooked beaks to tear flesh, and a roof of the mouth as well as a tongue lined with wickedly sharp keratin spikes, they have become the apex predator of Serina's global oceans by the early Cryocene. Kingfins occur in all oceans, though are only rare visitors in equatorial waters. Cold, temperate oceans are their primary habitat, for it is here that the seas are turbulent and mix at all levels, upwelling nutrients from the sediments below to feed blooms of plankton that form the basis of the rich oceanic food chain, a chain at which they sit at the very top. The largest kingpins can reach the weight of a killer whale - some 12,000 lbs - but this species is extremely dimorphic, with only males coming anywhere near such a size. Females are smaller, drastically so, reaching a maximum of only 1,200 lbs, with most most smaller still. There is no bird anywhere, on Earth or on Serina, with such a vast difference between the sexes. It has evolved, in this formidable sea predator, for one main reason. That reason is related to the unique way kingfins and all birdwhales reproduce, by brooding their eggs within a protective pouch in their throats, which has let them sever all ties to the land and spend their whole lives at sea.
In related species which feed on plankton or on plants, both male and female can continue to forage whilst carrying an egg, while putting it at little risk of harm. This is not true for hunters which engage in battle amongst other titans each and every time they must eat. A brooding predatory birdwhale, as it fights to overcome its formidable and very large prey with a deadly bite faces its defensive struggles all the while, is almost certain to break its egg in the process of prey capture. While it was possible for pairs to alternate caring for an egg, so one can hunt while the other stays back and watches the "nest", this was also untenable when multiple individuals needed to hunt together to have any success against big game. So kingfin ancestors found a novel solution by splitting up responsibilities between males, which tended to be slightly larger already, and more maneuverable females. During brooding, females would pass their eggs to the male, who would then brood the eggs for the entire 12 week duration of the incubation period, spending it primarily close to the surface. Females would do all hunting, feeding the male in turn, while he was better adapted to defend himself and the egg against other predators due to his larger size making him less of a target.
Millions of years of natural selection would gradually reshape the kingfin's own body and their social behavior. Males ballooned up in size, becoming so big that absolutely nothing could threaten them whilst protecting their eggs. Females stayed relatively small, but focused on cooperative hunting in large packs of other females to compensate. This worked out, for as males became larger, the carrying capacity of their pouches also increased, letting one male serve as an incubator for the eggs of up to 10 females at one time. In contrast to many species in which single males fight over and defend groups of females, the roles have become partly reversed in the kingfin, as the huge males are now highly coveted by female packs, which will fight fiercely to hold onto them. Males do not fight females, instinctively accepting new members into the clan without a fuss, even if they are rivals seeking to steal him from his previous mates and take him for themselves. So it is up to the female kingfins to defend their mate from usurpers, just as he protects their young from predators through his sheer size. Most clans only require one brooding male, and it can become a substantial burden to support any more than this, but in the most productive polar waters larger clans can form in which over 30 females may accept up to three males. The integration of a second or a third male can be difficult, as males will naturally defend themselves from rivals with powerful strikes of their front flippers - a form of combat that prevents them from biting and breaking their brooding eggs. It is most likely to occur if the additional males are much younger than the original one and highly submissive, or if they are related and come from the same bachelor clan. Intelligent animals, these birdwhales can recall old relatives even after years apart.
Because clans are structured with up to ten times as many females as males, there are always such bachelor groups that travel the seas looking for females that need a new male to join them. They can at times be aggressive, and may even try to displace a resident male by attacking him, but they rarely win as birdwhales grow throughout their life. The largest naturally tend to be favored by females, so that such roving bands of unmated males are often much younger and smaller and ineffective in one on one conflict. Combined with the aggression of resident females, it is rare that wandering males bear a resident male and take his place, and if this does occur the females may or may not accept the change of leadership. They are much faster than the males, and easily dodge them. They may simply follow him to new territories anyway, as their social bonds are strong. Because the females cannot be controlled by the males, males have much less motivation to aggressively compete for their favor than in many other animals. They are much more likely to try and draw female's interest with showy displays of their fitness involving breaching out of the water and even "singing", producing eerie, wide-reaching calls through the deep oceans that sound somewhat like distant, distorting foghorns.
When the small young begin to hatch, they may weigh just 40 lbs, among the grandest differences in size from young to adult of all birds. He holds his beak open at the surface as they hatch, so they can breathe, and then ensures they stay here and take their first breaths. Soon, they are active and can swim freely, and they form a creche around him whenever their mothers are away hunting. He becomes a babysitter, and he may "swallow" them up again if necessary to protect them from roving predators thereafter in the time period between when they leave their eggs and when they are strong enough to begin following their mothers and learning to hunt, keeping them safely sheltered in his mouth and held above water so enemies cannot steal them. But once the young are born, the male is no longer relegated to full-time parenting duty, and now he will also leave the chicks with the females periodically and do some of the hunting. Particularly as the babies grow larger, they begin to require much more food. So the male earns his keep then by hunting even bigger birdwhales than the females can, bringing down adults of the biggest of all sea animals single-handed with his astonishingly powerful bite, and then leading his family to the kill to feast. Females may have to hunt three or four times a week to feed themselves and the male during incubation. But when a male is freed to do the hunting, a single huge kill can sustain them all for up to ten days. And once no longer encumbered by carrying eggs in his throat, a male becomes a real force to be reckoned with. Nothing will dare come close to his offspring now, for he will rip any enemy to pieces with the strongest bite force of any living animal. He may not rule the family, which is matrilineal by default.
But he is still the most powerful of all the sea's mighty creatures today, the king of the deep blue.