This is a thing about dragons in my setting that I wrote a while ago. For some reason it is written from a modern, scientific viewpoint, which makes no sense since the story is a medieval fantasy.
‘Dragon’ is not used to refer to a specific species, instead it is a colloquial term for any large, carnivorous, fire ‘breathing’, or otherwise fire producing animal. There are three genera of acknowledged, but largely unrelated, ‘dragons’.
Perhaps the best known are the wyverns, the large flying monotremes, mostly native to the isolated southern continent of Sunda. The somewhat inaccurately named Common Wyvern, so called because its cosmopolitan range meant it was known to science long before its relatives, is the classic example of this form of dragon. They are capable of producing flame, which they use primarily to defend themselves and their young when they are vulnerable on the ground. They are magnificent creatures, with wingspans of up to fifty feet (16m), and weighing up to 500 lbs (225kg). Mature males rely more on their venomous heel spurs, both for defense and battles for dominance with other wyverns. This venom is famed for its extreme pain inducing capabilities. They are highly intelligent and can easily kill humans, though in recent times examples of attacks are rare.
A wide variety of related species are found on Sunda, most of them much smaller, only a few of which have the fire 'breathing' adaptation. Diversity is especially high along the Bornfjord coast, home to some of the richest marine environments on the planet and is thought to be the location where the large, predatory wyverns evolved from smaller, bat-like forms, commonly found on elsewhere on Sunda. The group originally evolved from cat sized arboreal ambush predator that used skin flaps to control its trajectory while pouncing, on a continental fragment island that would eventually become part of modern day Sunda.
Their bodies are covered in a dense coat of soft fur, providing warmth at high altitudes and in winter, usually dark brown or black in color, except the throat. Their membranous wings are quite sensitive and can be minutely adjusted to enhance soaring efficiency or maneuverability, this ability makes wyverns the most efficient gliding machines in history, but it does come at a serious cost. Such a wide expanse of thin skin rich in blood vessels has formidable potential as a radiator, one might expect wyverns to freeze quickly if they attempted to fly in cold climates, but this is not the case. A fine coat of down on the wing membrane helps to insulate them, in addition they can restrict blood flow to the wings to reduce the heat loss. The wings can also serve as solar heat absorbers, this can help offset the cooling affect. In warmer climates, wyverns are careful to regulate their heat exchange to maintain optimal body temperature, the wings again function both as heat absorbers and radiators, modifying blood flow to different sections of the wing is used to keep temperatures stable.
Analogous to birds, though clearly a case of convergent evolution rather than homology, as clearly demonstrated by both phylogenetic and anatomical evidence, wyverns have air sacs that create one way air flow, increasing respiratory efficiency, an essential adaptation for such a large flying creature.
Some of these air sacs have been commandeered to function as fire breathing mechanism. Air sacs in the throat have been separated from the respiratory system, and merged with modified salivary glands that originally to produce a noxious spit that nestlings used to defend themselves. This organ houses the flammable phosphorus compounds. When needed, violent contractions expel the inflammable mixture with enough force to push the cloud of burning gas and particles out and away from the mouth of the wyvern. This cloud will spread out and extend up to 15 meters, though most of the gas will have burned off by that point, only the white, smoking, phosphorus particles are likely to hit at that distance. But being hit with white phosphorus particles alone is still a horrific experience, they burn hot, easily penetrate skin, and are difficult to extinguish. In addition to the terrible burns that can be inflicted, the smoke produced by burning phosphorus is an irritating desiccant, and the overdose of phosphorus in the blood stream of a victim can lead to liver and kidney failure even if they survive the burns. This proved to be a more effective defense mechanism and came to be retained into adulthood. Wyverns absorb extra phosphates from their food, especially bones as the mineral component of bone is hydroxyapatite, a calcium phosphate compound, as well as sometimes eating phosphorus rich minerals, or bird guano. The excess phosphates, those not required for cellular metabolism or bone growth, are channeled to the throat sacs where a complex series of reactions, partially performed by symbiotic bacteria, where elemental phosphorus (aka white phosphorus) and phosphine are generated, and stored in a anaerobic, sealed chamber. The two flame ducts are clearly visible on the neck of the wyvern, as ridges extending about halfway down. The neck of wyvern has red and black warning coloration, typically the vertical red stripes follow the path of the flame ducts. The ducts merge under the jaw and the opening, which is typically closed and unobtrusive, is beneath the tongue, at the very tip of the jaw, allowing the gas and particles to be expelled without striking the mouth. The ducts are well reinforced, lined with a protective coating, and kept free of oxygen that could ignite the deadly fumes.
Wide ranging, effectively cosmopolitan, all the world's Common Wyvern populations form a single, interbreeding gene pool. Wyverns hunt essentially anything, but due to their size they prefer medium to large prey items, above 10 kg. They avoid dense forests, for the obvious reason of their enormous wings are unwieldy in such cramped quarters. Wyverns prefer plains or sea coasts, where they can soar and locate prey easily. They are also fond of mountains, which provide inaccessible roosting and nesting areas, as well as open meadows where hunting is possible.
The hunting strategy of wyverns is fairly straightforward, they soar at high altitude, scanning the ground for prey, then they stoop on it, striking with their three major talons, the impact of nine inch long claws at fifty to sixty miles per hour is suitably devastating to kill even large animals. If the prey is small enough it will simply be snatched from the ground and carried to a roost, or even eaten on the wing. If it is too large to carry, which a large proportion of the typical Common Wyvern's diet is, they will eat their fill at the kill site, if possible tearing off chunks to carry back. Male wyverns are able to take even the those few creatures that are too large to be incapacitated by a high speed strike, with their venomous spurs. Wyvern venom will incapacitate many tonned creatures like elephants or even whales, and the impaired animals killed by talon or fang. Right or bowhead whales are sometimes taken as their bodies float and can be easily consumed, though killing a creature a hundred times its size is an enormous challenge. Other large whales, rorquals or gray whales for example, would sink and the hungry wyvern lose a hard fought meal.
When on the ground they are vulnerable to attack, wyverns are quite large and strong, but lightly built, and could be badly injured or killed by a number of potential attackers. This is where they pyrotechnic capabilities shine,a burst of flame, mixed with burning flecks of phosphorus wards off even the fiercest assault. Fire is rarely used for hunting because the flames can consume delicious flesh and it may become tainted with reactive phosphorus compounds. While wyverns are more resistant to forms of phosphorus poisoning, and can absorb large amounts of phosphates and transport it to the fire glands, it is still possible for them to suffer ill effects.
Wyvern legs and feet are well adapted to the needs of the animal, they are very powerful, and make wyverns both rather adept on the ground and able to rapidly get into the air with a leap. They have five toes, the largest two point forward and have only small, blunt claws. These two toes are very robust and bear the animal's weight when on the ground. The other three oppose each other, two connected together pointing backwards, held above ground when walking and used as main striking weapon when diving. The third is next to the two walking toes but held upwards, opposing the main two talons. All three bear large sharp claws, for gripping and tearing. Unlike some of its smaller relatives, the wyverns wing membranes do not extend over its legs, instead the legs are positioned beneath the body, with the wing membranes extending over the hips to the end of the, rather short (less than a third the body length, or roughly 1.5 meters long) tail.
The neck is long, and flexible enough to allow to reach prey held in its claws and slightly longer than the tail, but to its length most be added the large, though airy, and fearsome head of the beast, the anterior section of its muzzle consists of sharp, serrated, keratinous 'teeth' in parallel rows, culminating in the two large fangs at the tip. Behind the 'teeth' are similarly keratinous pads, used for crushing bone. This is an extensive modification of the ancestral bill structure, found in a different forms in the other extant monotremes, the duck bill of the platypuses, the long snout of the echidnas and the broad grazing beak of the hekgris(a group of large, spiny herbivorous relatives of the echidna). Fossil evidence suggests that the common ancestor of modern monotremes had replaced its canines and incisors with a horny beak. In the platypuses and echidnas all other teeth were eventually lost, but wyverns retain shearing carnassial teeth in the back to slice up their meals.
Wyvern social groups are very both highly variable and quite complex. As all wyverns belong to a single interbreeding population, it seems that individuals are able to adapt to different circumstances and alter their behavior when dispersing to areas with quite different group dynamics. The core unit of wyvern interaction is the family group. Wyverns do not always mate for life, but pair bonds are generally very strong. There are many instances of a wyvern who's mate or young have been killed launching apparent revenge attacks, usually resulting in many casualties and the death of the wyvern. Some advocates have gone so far as to state the wyverns never attack humans except in these revenge attacks, though this viewpoint is quite clearly contradicted by a number of reputable sources. Less well recorded in official documents, but attested to in the folklore of completely unrelated cultures on separate continents, is the tale of a widowed wyvern pining away to death over its lost mate. No instances of this behavior have been observed by reliable witnesses. These wyvern family groups can either consist of parents, the most recently hatched young and adolescents that have not yet dispersed, or larger collections, that, although they spread out over their large territories to hunt most of the time, nonetheless collect together again at night, and usually nest nearby. These larger groups, called clans, often, but not always consist of related individuals, with their mates generally coming from other populations. Unlike many other social species, both sexes disperse after adolescence, sometimes only to the neighboring clan, sometimes to the other side of the world. Radio tracking has shown that some wyverns return to their natal clans after bonding with a mate, sometimes after a journey spanning the globe multiple times.
Whether a wyvern belongs to a clan, and return to their natal family following dispersal, or a smaller family group where post adolescents rarely return to their parents, is not completely understood but appears to be, at least in part, connected to the natural resources of their territories. Rich hunting grounds, for example the Bornfjord mountains, where territories can extend over both the rich kelp forests to the north(providing large fish, like salmon, seals, sea cows, and dolphins and porpoises) and the steppes (providing herds of reindeer, mammoth, horse, saiga antelope) generally have a clan structure, while less favorable areas have a single family structure. It would seem that clans only develop where a threshold density of wyverns can be supported. Unlike other cosmopolitan fliers, like albatrosses, wyverns do not have a single, or small number, of breeding colonies that they return to again and again. Instead nesting occurs throughout their range, wherever a somewhat isolated and inaccessible location can be found, mountain caves are particularly suitable, and inadequate ones expanded by the strong claws of the wyverns, though in some circumstances even that is necessary, one clan of wyverns was known to nest communally out in the open, the twenty to forty wyvern adults and adolescents providing sufficient protection. Unfortunately, or not depending on your perspective, this group was forced to abandon its territory by human disturbance. Indeed, human disturbance has proved so antithetical to wyvern nests that in most of the Eastern continent, many wyverns nest elsewhere, in large colonies, approaching the scale of seabird colonies, on distant islands or crossing the seas, migrating temporarily to one of the other continents. This later tactic can lead to intense confrontations as they encroach on the indigenous populations, and the first to considerable stress with the vastly different social arrangements such a nesting colony requires. Those few that still nest in the Eastern Continent have moved to the most rugged and forbidding mountains to escape persecution.
As monotremes, wyverns lay eggs, large, oval, leathery eggs, generally two, roughly a meter long, that hatch after roughly two months, following two months of internal development. The mother incubates the eggs, being fed during this period by her mate and their immature young. They have mammary glands, but lack teats, instead they have two patches of skin with pores, where the nestlings can suckle. Their mother can now leave the nest to hunt, but typically one wyvern stays near the nest to protect the nestlings until their flame glands develop and they can be supplied with the required components. They nurse for up to a year, growing rapidly in size. They will stay with their parents for another four years or so, until the next set of nestlings fledge. Dispersing subadults are generally near their adult size, but will continue to grow and mature as they travel. This is one of the most dangerous periods of a wyvern's life. They must cross unknown territories, dealing with challenges from the owners of those territories, and if they travel far enough and many do, new prey animals. One popular destination for these young wyverns is the edge of the northern ice pack. This is a rich environment, in the summer at least, with abundant marine resources. It does not sustain a breeding population of wyverns because the small, icy rocks that are the only land in the north of 60 degrees north, provide no suitable nesting sites and the summer is too short for a wyvern nestling to mature before the bitter winter would freeze or starve it. It is a near perfect place for immature wyverns gorge under the midnight sun however.
The other ‘Old World’ dragons, are large pythons that produce a flammable, sticky substance that they can spit with considerable range and accuracy. This spit is ignited as it is expelled through a 'flintlock' mechanism, where a special iron coated organ strikes a mineralized section of the snakes palate and can be used to kill prey, defend against predators or battle for dominance with other members of its kind. Most prey however is taken by constriction, sometimes the methods are combined; other times the flame is used to force a large prey animal into the water, in an attempt to douse it, and thus the waiting jaws of the wyrm. The largest examples , over 10 meters, are exceedingly dangerous, heavily armored, scarred and charred from countless battles, motionless, invisible in the jungle, they can launch up to a liter of burning sputum nearly 40 meters. The mechanism behind this liquid hydrocarbons, thickened with latex.
The final, least well known, and generally least dangerous, ‘dragons’ are mekosuchine ‘land' crocodiles found on the savannas of the western continent, the fire ‘breathing ‘ actually producing a flammable gas in nasal glands, used for defensive purposes. This ‘dragon’ is relatively small by comparison to the monsters also known by the name dragon, rarely reaching 3 m in length, including tail, and 150 kg, providing the basis for their common name, the pocket dragon. The glands produce aniline and hydrogen peroxide, in separate chambers , these mix when snorted out, producing a burst of flame.