Few non-dinosaurian animals are as invocative of the Mesozoic as the pterosaurs, the ancient flying reptiles and first flying vertebrates to have ever existed. Pop-cultural "pterodactyls" may look nothing like the ancient flying animals, creatures as sophisticated as the dinosaurs and mammals, but these inaccurate depictions still capture an omnipresent feel of these animals: no primeval scenery is complete without pterosaurs flapping around.
In Spec, the history of pterosaur research has probably been one of the most convoluted and bizarre scientific affairs in history. When the first specexplorers ventured into, well, Spec, they weren't treated to ancient landscapes with skies filled with "pterodactyls". Few were shocked: for the longest time, it had been thought that pterosaurs were declining in the latest Mesozoic, and even as new research showed a higher diversity of terminal Mesozoic forms than previously thought, to many it was simply the confirmation of an inevitable reality. A skull dating from the Palaeocene - one of the very first Spec fossils found - found in a random Pacific Northwest beach was revealed soon after; crowned *Gigantala cranitus*, it was for a while considered the last of Spec's pterosaurs.
However, after research started being conducted in more landmasses, and as closer inspections of Spec's habitats began, pterosaurs were in fact confirmed to be in Spec. First, the expected azhdarchids showed up, fairly conservative after 66 million years of evolution, followed by the tremendously derived australian carnocursorids (for the longest time assumed to be azhdarchids). This was followed by unexpected discoveries: two clades of previously "thought to be long gone" pterosaurs were discovered (though, since one of said clades was previously known to have survived as recently as the Turonian and both were fairly cryptic and poorly understood in HE's fossil reccord to begin with, in retrospect such amazement wouldn't have been warranted), clades that not only survived, but surprisingly diversified considerably. Finally, Spec's researchers had the confirmation that nyctosaurs are indeed still around, in washed up carcasses.
In total, 60 pterosaur species have been discovered, though the number is still increasing, and might indeed do so very significantly the more we research the pelagic nyctosaurs. The exact flux of pterosaurian diversity after the Late Cretaceous is not clear, as the fossil reccord follows similar trends, but in the laggerstate rich fossil reccord of the Eocene we do observe an immense variety of forms, including groups such as ctenochasmatoids and chaoyangopterids, displaying a morphological diversity not seen since the Lower Cretaceous. The Oligocene is poor outside of ornithocheirid and carnocursorid fossils - the latter mostly from Riversleigh -, but the Miocene depicts a fairly diverse variety, with eastern Europe in particular showcasing a wide variety of genera. Of the Miocene pterosaur forms, only ornithocheirids are absent in the present, with the last remains being mid-Plestocene japanese and New Zealand subfossils.
Pterosaurs are some of the most derived sauropsids - and amniotes, for that matter - ever known. About the only thing certain about their anatomy is an identity as archosauromorph diapsids, sharing the dual temporal fenestrae, perforate jaws, antorbital fenestrae and several minute traits in the neck, vertebrae, pelvis and hindlimbs with other such animals, including dnosaurs and crocodiles. Genetic studies in Spec's living pterosaurs confirm that they are true archosaurs, nested alongside dinosaurs and crocodiles, ad slightly closer to dinosaurs than to crocodiles at that, which can possibly infer several shared traits between both dinosaurs and pterosaurs as characteristics shared by their last common ancestor. Both groups composed the clade Ornithodira, the "bird like archosaurs".
The most notable feature pterosaurs have are their wings. Once believed to have been simple leathery structures akin to [spec]bat wings, pterosaur wings are ostensibly the most sophisticated wings of all known animals, something that goes without saying after over 230 million years of evolution. The wing is composed of a membrane that stretches across the limbs, down from the ankle to the tip of the animal's single wing finger - pterosaurs have four fingers, three remaining as claws, the fourth converted into a long, clawless, curved structure that supports the dystal part of the wing membrane, forming a "blade" of sorts. This membrane is thin, but inside it several layers exist. The first layer is composed of the aktinofibrils, collagen fibers that striffen the membrane and prevent it from fluttering around when the animal flies or glides; they radiate from the forelimb, mostly from the hand and wing finger, giving a vague resemblance to the wing feathers of birds, and in modern species are generally bifurcated. The second layer is composed of muscle fibers, that reduce the surface area of the membrane as they contract, allowing the animal to change the shape of it's wing in flight - offering a huge advantage over birds and flying mammals with their fixed wing shapes - as well as retracting the membrane away when the animal is on the ground, preventing it from being a problem when running. The third layer is composed of blood vessels, some having unique looping forms. The number of additional layers of aktinofibrils, muscle fibers and blood vessels varies from group to group.
Pterosaurs, like most other flying vertebrates, also have a propatagium and an uropatagium, which are rather simple membranes compared to the main brachiopatagium, without the complex layers. Pterosaur limbs vary drastically, even for the standards of flying animals: the hindlimbs are rather conservative, being plantigrade and lacking complex musculature in the foot - this, coupled with the rather flat and inflexible nature of the toes, prevent real pterosaurs from grasping prey or perches like birds and flying mammals do -, while the forelimb has changed drastically to suit the funtion as a wing, becoming far more robust and developing several adaptations unseen in even other flying vertebrates. The humerus is generally short, robust and stout, possessing huge dectopectoral crests to serve as an anchor for flight muscles, while the metacarpals elongated, like those of ungulate mammals, only unpronated and having a different bias, with the fourth metacarpal being massive in comparation to the others, being where the wing finger comes from. An unique bone, the pteroid, formed from the carpal bones, being a long, curved rod in the image of the wing finger, only much smaller, serving to support the propatagum. Pterosaurs frequently suffer from arthritis in old age as they wear their carpal joints due to the stress of powered flight. As the hindlimbs also support the brachiopatagium as well as the uropatagium, they function not just as extensions of the wing, but also as the main steering devices; as such, they can be risen completly horizontally, unlike the fixed hindlimbs of other archosaurs, and thus do not have the unique fixing joints of their relatives. Nonetheless, pterosaurs have an erect limb posture when walking.
As quadrupedes like most other flying vertebrates at the expense of birds, pterosaurs not only gallop around in all frous, they can also launch into the air using the forelimbs, an act particularly effective in these animals thanks to their long metacarpals. This saves energy and doesn't make the development of unecessarily heavy hindlimb musculature necessary, and as such pterosaurs waste much less energy than birds when launching. This both allows them to reach much larger sizes on average, as well as retain flight whilst exploring terrestrial niches. On the history of pterosaur evolution, only one clade is known to have lost flight, the australian carnocursorids, and even they remain partly volant in their early stages of development (keep reading).
Pterosaurs share with dinosaurs a complex airsac pulmonary system, allowing them to breathe efficiently in an uniflow air path, though in pterosaurs it's even more extensive and refined. In several species, the airsacs extending into the membrane, running along the forelimb, helping to pneumatise it and even acting a role in extending and retracting the wing membrane. Pterosaurs retain gastralia, and have bizarre "squiggly" sternal ribs, both supporting diaphragma-like muscle systems that help pump the air across the pulomnary system more easily. The sternum is keeled, but often relatively shallow; unlike Neornithes, and like most other flying vertabrates, pterosaurs rely more on muscles attached to the scapula and back to raise the wing, with only the muscles that pull the wing down attaching to the sternum. The tail, in modern species very reduced and small, lacks the musculature associated with the tails of other tetrapods, have a reduced caudofemoralis, and are more mammal-like in terms of hindlimb musculature.
The neck is also rather mammal like, being sorrounded by powerful muscles instead of the thin avian musculature; likewise, pterosaurs only have nine cervical vertebrae, three of them "dorsalised" while the others supporting the neck and head. The main seven cervicals vary in shape and size, with a tendency in modern species of being rather long and shallow, offering very giraffe-like necks, albeit somewhat more flexible. Pterosaur neck vertebrae have unique pneumatic foramina, which allow the invasion of airsacs into the bone, making them hollow. Pterosaur skeletons are pneumaic like those of dinosaurs, and have honeycomb-like internal structures that make them surprisingly strong. Even species with only milimetre thin bone walls have very hard bones, in some bases breaking theropod teeth.
The skull is by far the most diverse part of the pterosaur anatomy, with a wide variety of jaws and crests. Pterosaurs have rather simple skull bones compared to those of other archosaurs: modern species only have one opening in front of the eye socket, the nasoantorbital, which in most species enlarges the skull significantly, whilst the perforations on the lower jaw were lost early on in their evolution. In addition, the bones sutures are fused so completly in in most modern species, pterosaur skulls are basically composed by two bones, the skull and the mandible. Pterosaur jaws vary wildly like those of birds, with an impossibly high number of tooth and beak combinations and shapes. Pterosaur teeth are replaced constantly like those of other sauropsids, but the replacement is rather unusual, with new teeth appearing behind older teeth instead of underneath them, dampening the effects of tooth loss as new teeth reach up to 60% of their maximum size before the older teeth are lost, allowing a semi-constant presence of teeth. Nearly all known pterosaur groups have had headcrests, usually composed of keratin, with or without a bony support.
As endothermic animals, pterosaurs have fur-like integrument, known as pycnofibrils, very similar to mammalian fur but much less deeply rooted in the skin. Homology with dinosaur feathers has been suggested, implying that the last common ancestor between dinosaurs and pterosaurs had fur-like integrument, though pycnofibrils are structurally differently from the most primitive feathers. Pterosaurs have a wide variety of pelages, usually tending towards thick coats, that have the same colour constraints as mammals, as most pterosaurs can't absorb carotenoids. Also like mammals, pterosaurs have foot pads, though usually covered with scales.
Pterosaurs have similar digestive systems to those of dinosaurs, with a gizzard where gastroliths triturate food. In lieu of pelican-esque pouches as often historically suggested, pterosaur esophagi can extend immensely, allowing the animals to consume quite large prey, storing it in the neck. An ancient clade of pterosaurs, the "campylognathoidids", did in fact had what appeared to be molarfiform teeth proper for mastication, but no modern pterosaur can chew.
Pterosaurs lay eggs with rather thin eggshells like those of squamates, usually barely calcified. Some species have been able to develop vivipary, a trait seen nowhere else among archosaurs. Like most sauropsids, pterosaurs are highly precocial, being able to fend for themselves since birth - they, alongside some non-euornithe birds, are the only vertebrates to be able to fly since birth -, and thus have slow growth rates, occupying several ecological niches as they grow. Even small pterosaurs may take several years to reach sexual maturity like opposite-birds, and they still keep growing several years after being able to breed, though they eventually reach a maximum size.
The pterosaurian brain is rather bird-like, with larger flocculi and slightly proportionally smaller. Pterosaurs have a rather complx nervous system across their wing membranes, reponsible for both controlling the muscle fibers as well as detecting changes in air pressure. Being generally social animals, most pterosaurs engage in a variety of complex behaviours.
All of Spec's pterosaurs are pterodactyloids, which have obscenely long metacarpals, a well developed notarium, the fusion of the antorbital fenestrae and the nostril into a single opening known as the nasoantorbital, highly reduced tails, elongated neck vertebrae, large pteroids, the lack of cervical ribs, simple dentitions, and very short fifth toes (in previous pterosaurs, these supported large uropatagiums that united both legs; in pterodactyloids, the shorter fifth toe means a clearly divided uropatagium, often highly reduced in some species). While not a feature ancestral to pterodactyloids and in fact absent in many historical groups, all modern species have airsacs on their wing membranes, stracting along the forelimb at least.
Although often considered the "model pterosaurs" via the abundance of pop-cultural depictions of *Pteranodon* and ornithocheirids, the truth is that these are rather aberrant pterodactyloids. Specialised for powered flight above other forms of locomotion, ornithocheiroids have very tall shoulders, generally very large wings, small hindlegs, small bodies, blocky humeri with very large dectopectoral crests and robust wrist bones. Their necks tend to be more flexible than those of other pterodactyloids, with shorter vertabrae with strange triangular structures for muscle attachment, though obviously nowhere as flexible as dinosaurian necks. Unlike other crested pterosaurs, ornithocheiroids don't have large keratin crests, having simply bony crests without any soft tissue extensions.
Through most of the Cretaceous, ornithocheiroids were the dominant piscivorous pterosaurs, with some forms like istiodactylids and boreopterids branching into stranger niches on inland biomes, the former as scavengers akin to modern harpies and gorgeese and the latter as lacustrine swimmers. Aside from azhdarchids, ornithocheiroids were the most prevalent pterosaurs in the Late Cetaceous, and enter the Cenozoic with a wide array of species. The Eocene and Oligocene appear to have been their Cenozoic golden days, in the latter completly replacing azhdarchids as the most common pterosaur fossils. In the Miocene, ornithocheirids and pteranodontids are less common and eventually disappear, but boreopterids, pteranodontids, azhdrachids and nyctosaurs remained to the modern days.
Boreopterids first appeared in the Barremian, where the only certain Mesozoic remains come from. However, their post-cranial skeleton is so similar to that of ornithocheirids that many supposed ornithocheirids might actually be boreopterids, including several Late Cretaceous remains, which occur in inland freshwater ecosystems, favoured by these pterosaurs. The Eocene has them unambiguously resurface, with some Miocene/Pliocene fossils also clearly being boreopterids; a great number of ornithocheiroid finds from the Paleocene, Oligocene and Miocene may either be boreopterids or ornithocheirids.
Boreopterids are, however, still rather distinct and strange animals. Adapted mostly to live in inland lacustrine environments, boreopterids in general tend to have shorter wing fingers than their relatives, resulting in shorter and broader wings (when the wing muscle fingers aren't contracted, at least). With elongated, warped dectopectoral crests and reinforced scapulae, boreopterids are capable of water based launching, using their powerful forelimbs to propel themselves into the air, and their feet are small even for ornithocheiroid standards, poorly suited for walking. Boreopterids thus spend most of their time in water, using their forelimbs to both fly and to swim, either as rows or by aquaflying, the hindlimbs serving in steering, both on air and in water. More bizarre, however, are their teeth: thin and long enough that they project well beyond the bounds of the jaw margins when they close, they are poorly suited to grasp and stab prey, but optimal for trapping small animals in large numbers like a net. Some species have properly developed filter feeding, increasing the tooth number in one jaw at the expense of the other and developing powerful jaw muscles to pump water in and out of their mouths as they "bite" through the water.
About four species are alive today, distributed across the tropics and subtropics.
Granduke (Ketochasma fritzli)
The Granduke is a presence on the wetlands of most of Africa and southern and western Eurasia, occuring from the Mediterranean to the Ganges and into the Caucasus' inland seas, with occasional breeding populations making a living as far East as the Baikal and as far west as Brittain; most of the extremes in it's range usually occur in breeding and wintering seasons, when these pterosaurs migrate huge distances and are taken to explore new territories. With a 4.5 wingspan and standing at 2 meters of height, the Granduke may not be huge by pterosaur standards, but it is the largest living boreopterid and one of the largest known members of the clade, and certainly a very impressive animal, on the air or on the ground. Occuring in a variety of freshwater habitats, from estuaries to swamps to highland lakes, it tends to preffer large lakes, where it can gather to quite large flocks. It's thin, baleen-like teeth are focused on the upper jaw, and are hidden by lower jaw protrusions when the mouth is closed; like most pterosaurs, most of the jaw displays a very long mandibular symphysis, preventing the appearence of a pouch. This doesn't detriment the animal much, however, as water is simply pumped in and out as the animal "bites" through the water like a flamingo - which also share a similar jaw structure, with the "baleen" on the upper jaw hidden by lower jaw protrusions and with an extensive mandibular symphysis. It has a rather catholic diet, with anything from small crustaceans to fairly large fish being trapped within it's jaws.
The Granduke's crest is rather oddly positioned for a boreopterid, forming a disc in the jaw tip, not too dissimilar from the crests of the typical ornithocheirid. In males, this crest is predictably bigger, but it is also wider and has a more robust internal support. More bizarrely yet is how these crests are used; contrary to what one may think, there is very little animousity between adult males, which are content with foraging alongside each other. They instead have a much more simister purpose: males strike at females with these crests, ramming their robust jaw tips against them, bruising them until they are too weak to fight against anatid-style violations. At times, groups of males may gang up, isolating females from groups and beating them with the crests in all directions, causing severe bruises. In the breeding season, females may even be rounded up in groups, guarded by several males that prevent escaping and help subdue the rape victims.
This seemingly barbaric method is observed occasionally in HE dolphins, but the Granduke seems to have taken it to it's logical extreme, the tendency for forced intercourse having evolved into a grotesque herding strategy. How and why these pterosaurs switched from male rivalry in lek systems to cooperation in herding and gang-raping the opposite sex is unknown, though the presence of similar crests in some extinct relatives may suggest it has began as far back as the Eocene. It has been suggested that this is simply the logical conclusion of the sexual selection expressed in rape strategies, where an arms race of male and female strength determines if the male's genes will be passed on to the next generation.
Although adult males do not act violently against each other, as sexual competition is detrimental in a scenario where cooperation is vital, younger males that haven't yet reached sexual maturity are fair game, often raped and rounded up alongside females. After they reach sexual maturity, they may join males of a specific group, or move elsewhere. The Granduke is also not limited to animals of it's same species: several animals, from ducks to juvenile mokeles, may also be gang-raped and often die of internal organ fracture.
Thankfully, these strategies only occur in the first month or so of the breeding season: afterwards, males stop herding females, which are free to go away and move to the safety of larger flocks, if they aren't too wounded. They gather in large numbers in sandy bars and river banks, burying their eggs, often alongside crocodiles and turtles. At least a few females remain nearby, helping to fend off predators. After an incubation period that may take up to three months or so, the juveniles are born, enough nests incubating at the same time to ensure predators only get a small fraction of the flaplings. They stay near the adults, even migrating alongside them, foraging on aquatic insects and small crustaceans. Half an year later, they're about a quarter of the adult size, growing slowly for about three years or so until they reach sexual maturity, and continuing to grow for about three more years.
Trausduke (Ctenornithosaurus moorei)
Occuring across the Americas, the Trausduke is a smaller relative of the infamous Granduke. With a more conservative set of teeth on both the upper and lower jaw, it nonetheless occupies a similar ecological niche, trolling the waters of rivers, lakes, marshes and bays, and trapping fish and crustaceans in it's jaws; it often also dives, pursuing prey underwater by aquaflying. Males have a crest that extends along the upper jaw, tallest near the end of it, and engage in the more usual pterosaurs lek system. The Trausduke is a rather migratory animal: part of the year, the population has a more northern range towards North America and is rarer in South America south of Pantanal, while during another part of the year the focus becomes reversed, disappearing from most of North America and extending it's range southwards into Patagonia. Such shifts are seemingly a recent phenomena, as the glaciations presented a more narrow band for these shifts, and indeed it actually appears to have been largely sedentary, occuring mostly in subtropical America.