On The Origins Of Flight: No Gliders?

All things considered, vertebrate flight is the ultimate triumph of animal bioengineering, producing active locomotion on the thinnest of availiable mediums, releasing the individual from the ground and opening it to an entirely new realm to navigate upon. Flight has led to massive adaptative radiations and ecological niches completly impossible for terrestrial or aquatic animals to explore, and it leads to exaptations for other credible feats, like extremely effective lungs and large brains. Flight is freedom, and there are ten thousand reasons as to why we pitiful land primates have envied birds, bats and insects, and most surely pterosaurs if they were still alive.

Yet, when one looks at the groups of flying animals that have existed, one thing becomes apparent: it’s very, very rare for an organism to develop true, powered flight. Birds, bats, insects and pterosaurs are and were incredibly speciose and morphologically diverse, but immense adaptative radiations were all resulted from a mere four successful attempts at being an aeronaut. All the +10,000 living bird species, and their possibly millions of extinct relatives? Descendents from a single dinosaurian aeronaut back in the Jurassic, whose aerial prowess quickly kickstarted an adaptative radiation more or less at the same time pterosaurs were during their golden age. Pterosaurs themselves, from the miniscule anurognathids to the ginormous azhdarchids and ornithocheiroids, all descended from a currently unidentified form of sauropsid that took to the skies in the Triassic, a single species possibly akin to Scleromochlus. Going hundreds of million years further in time, we have the single common ancestor of over 60% of all animal life on the planet, the winged arthropods, and forward in time to the earliest Cenozoic we have a small, shrew like mammal who has made ghastly wings out of it’s hands.

Four species. That’s not even 0.01% of all animal life, no matter how mind crushingly diverse their descendents would be.

The sheer minority of successful aeronauts becomes even more puzzling when one witnesses the incredible diversity of gliding and parachuting animals, both from the past and presence. Among synapsids, extensive gliding has evolved at least 11 times, with the earliest known gliding mammal known from the Jurassic/Cretaceous boundary, the bizarre Volaticotherium, while squamates have produced gliders among all major lineages, to say nothing of the sheer amount of Triassic gliding reptiles. Some frogs developed long toes and webs that seem like smaller mockeries of bat wings, while countless fish species have turned their pectoral fins with airfoils and taken to the air; in fact, one lineage of said fish, Thoracopterigids, are quite possibly the oldest vertebrate group to have taken into the air. To say nothing of all the spiders and other arhtropods that glide and parachute, with webs or sheer chitinous extentions, as well as of the pelagic flying squid.

Yet, once again, all this incredibly diverse menagerie has achieved nothing akin to the powered flight of birds, insects, bats and pterosaurs, with the possible exception of a few fish, which propell themselves into the air with their pectoral fins. Indeed, many of these groups have become extinct, with no known close relatives and certainly no radiation of aerial critters derived from them.

It has been suggested that the presence of aerial vertebrates would have limited the presence of availiable niches for experimental flyers, something that falls extremely falt when A) birds evolved at the peak of pterosaurian diversity and bats when birds were already very well established (and posssibly even further back, when pterosaurs were still around), B) the idea that any of these groups have ever outcompeted or competitively excluded each other is at best severel uncircumstancial, and C) there’s plenty of ecological niches each individual group has occupied that the others haven’t (i.e. birds haven’t ever produced robust, boar-like terrestrial molluscivores like dsungaripterids, bats have never produced freshwater filter feeders, et cetera). Gliding animals also don’t seem to competitively exclude each other, so there’s little reason why animals in between gliding and full volancy wouldn’t have enough ecological space to exist.

An alternative option is what is reflected by an examination of gliding animal groups: gliding simply does not translate into flight, simply never leads to powered volancy, and that the flying vertebrates we know and love, as well as insects, have simply evolved under extremely anomalous sets of behaviour completly unrelated to gliding.

This is what I’m going to explore today.

What Living Gliders Tell Us

Colugos are about as close to bat-grade as any known non-chiropteran mammal has ever got...and that's as far as they will ever go.
Colugos are about as close to bat-grade as any known non-chiropteran mammal has ever got…and that’s as far as they will ever go.

Living animals and their extreme speciation compared to their long gone cousins can be exceptionally deceiving when it comes to studying the past, but they nonetheless offer a few clues about how flight may have aroused within the known flying vertebrates. As mentioned previously, there is a conspicuous absence of gliding vertebrates in a state of tentative flight, while the few fish that jump using their pectoral fins are not related to any gliding species. This alone can be considered pretty damning for the hypothesis that flight evolved from gliding, though it’s obviously not enough to establish a certain correlation.

Among gliding vertebrates, we witness a very wide range of adaptations for aerial locomotion, from the simple membranes of Holaspis to the complex airfoils of gliding squirrels. Some of these gliders have gone into extra lengths to acquire aerodynamical prowess, developing elaborate tail rudders (Ptychozoon), unique structural support for their wing membranes (such as the cartilage spurs of several flying squirrels and the ribbed wings of several squamates), proportionally massive wings (colugos, Draco lizards, et cetera), and even airfoil adaptations convergent with the aerodynamic design of flying animals (Exocoetidae). Some of these critters can be considered true aerial animals of their own right, travelling long distances on air and spending a good portion of their time gliding, though of course they are far more limited than true flyers.

Within the massive variety of living gliders, it’s evident that some will never develop powered flight: the rib wings of Draco and similar squamates, for example, cannot develop the necessary musculature and articulation to form anything other than a simple parachuting airfoil, and indeed extinct sauropsids with similar adaptations didn’t seem to have gone anywhere beyond a few “one shots”. Likewise, as suggested by Mark Witton 2013, flight is presumed to be unlikely to develop in ectothermic animals, as a warm blooded metabolism is likely a necessary exaptation in order to provide for the energetic demands of true volancy. This leaves pretty much every single living non-mammalian glider alive today as invalid candidates for powered flight, and therefore ill-suited models for how flight developed in bats, birds and pterosaurs. Thankfully, the menagerie of living gliding mammals is large enough to supply enough samples as to determine whereas flight can develop from gliding or not. And within these, two groups in particular can be held in particular regard.

The first, erroneously named “flying lemurs”, are often described as the most aerially adapted of all gliding mammals and just a step beneath the full volancy of chiropterans, having a well developed protopatagium and uropatagium, very long limbs that produce a massive brachiopatagium, and even a significant cheiropatagium, the fingers being quite long and displaying well developed webbing; in total, a colugo’s patagium is as massive as geometrically possible (Kathy MacKinnon 1984), and all the animal needs to develop functional wings is to elongate the hand more. They are capable of gliding for as much as 70 meters without losing altitude significantly, and their wing membranes indeed often an effective aerodynamic profile, the propatagium angled in the same as as that of birds and bats (and, presumably, as in pterosaur), the fingers serve as bastard wings and the uropatagium as an effective rudder (see image above). Such is their aerial competence that they were for the longest time assumed to be stem-bats, a relictual lineage wrestled out of the skies by more derived chiropterans, but genetic and morphological studies firmly place them as sister-taxa to primates, meaning that they became aeronauts independently (fringe “megabats are primates” pseudo-science nonwithstanding).

Thus, instead of being “living fossils”, colugos represent a lineage of gliding mammals that came very close to volancy… and stopped right there. The fact that the oldest members of this clade may date as far back as the Paleocene, when the first recognisable bats flapped their wings, means that they presumably had enough time to go go an extra mile and become true flyers, though in the interest of fairness we do not know if any extinct dermopterans were capable of gliding and if the aerial adaptations seen in modern forms are extremely recent. Colugos are specialised folivores, so it has been argued that powered flight is simply out of reach for these mammals, as folivory provides relatively little energy input, and gliding is a supposedly cheap way to travel around, while flight is obviously very energy demanding.

However, recent studies showcase that gliding is actually very energy taxing for colugos (Byrnes, G., Libby, T., Lim, N. T.-L. and Spence, A. J. (2011)), wasting as much as 1.5 times more energy by travelling through the air than by clambering amidst the branches. Part of the reason this is so energy demanding is due to the need to climb in order to achieve enough altitude for the next glide, often needing to climb as much as 8 meters for a non-problematic 30-50 meter “flight”, trouble flying animals do not have to deal with. Indeed, based on the studies’ conclusions, flight would have been a relatively cheaper mode of locomotion, and likewise the one flying animal with the closest lifestyle, the hoatzin, manages to be a specialised folivore and waste relatively little energy by engaging in short bursts of flight, less impressive than the colugo’s majestic “soaring” but certainly without the need to climb 8 meters in order to move around.

Thus, flight in colugos would have been relatively advantageous, and yet they have not made any further leaps into volancy throught the Cenozoic.

The other group, the iconic flying squirrels, come right behind colugos in terms of aerial speciation. While not having such extensive patagia, flying squirrels have well defined propatagia, brachiopatagia and uropatagia, and most importantly they are the only gliding mammals that have elongated the forelimb – the first step into the formation of a true wing -, developing unique cartilaginous wrist spurs that support the dystalmost part of the brachiopatagium. True to form, this development makes them even better gliders than colugos, capable of “flights” of 90 meters and more, and are seemingly better at steering in the air (Flaherty, E.A.; M. Ben-David, W.P. Smith (2010)).

No similar studies have been performed on whereas they spend more energy gliding, but if the studies on colugos are of any indication then flying squirrels should logically be also subjected to the same energetic pressures. Being omnivores, they’re also in a better position to develop powered flight, and in fact they presumably would benefit more from flight, as it would reduce energy espenses and aid them massively when foraging. Flying squirrels are thought to be a monophyletic lineage dating to the late Oligocene, which would have granted these rodents enough time to develop powered flight. Yet, as obvious, they remain exclusive, if particularly specialised, gliders. Once again, competition appears to not be an issue: no bats, and indeed no birds or even other sciurids, forage in the same manner as flying squirrels.

A third, ancient lineage of living gliding mammals is represented by the anomalures. Relatively basal rodents, these animals have been around since the Eocene, and not only haven’t become true aeronauts, they are also relatively cumbersome gliders, having a small propatagium and a bizarre brachiopatagium supported by an elbow spur, that helps stabilise the membrane but reduces any significant expansion of it. Flight, in this case, might had been prevented by the “flaw in design” rather than lack of opportunity.

Gliding marsupials are recent arrivals, having evolved around the latest Miocene; with relatively simple wing membranes, gliding is still on it’s infant steps for most of these animals, let alone powered flight. Outside of these lineages, there are a vast variety of mammals that have been reported to parachute, but of these only the sifakas and their possible rudimentary patagia show any possible adaptations for aerial locomotion in living mammals.

With at least two long lived lineages of specialised gliding mammals with no significant ecological competition in the form of bats or birds, and that are subjected to ecological pressures that favour powered flight, as well as almost certainly several long gone and unreccorded gliding mammal clades, it appears that gliding in mammals is not conductive to powered flight. It is possible that the necessary step for true volancy, the wing stroke, simply does not occur to animals “hardwired” to keep the wing stable during gliding, making the very speciation for gliding ironically the very reason why powered aerial locomotion is out of reach.

Of course, to strike out living gliders is not enough to determine whereas gliding is inconsistent with flight. To this end, examining true flyers is of extreme importance.

What Bats Tell Us

Baby bats appearently flutter when airborne, which has been at times interpreted as a possible indicator that the earliest bats weren't gliding.
Baby bats appearently flutter when airborne, which has been at times interpreted as a possible indicator that the earliest bats weren’t gliding.

The idea that bats are not descendents of gliders goes as far back in time as Glenn L. Jepson’s Bats: Origins and Evolution (1970), but it was more recently explored in detail in Kevin Padian et al. 2011. Here, the observance of fluttering in juvenile bats, as well as the very early evolution of echolocation in these animals, has provoked a hypothesis that, rather than descending from gliders, bats evolved from cave-dwelling mammals that specialised in stalking aerial insects, using echolocation to guise themselves in the darkness and fluttering in order to control their descent. While without doubt a rather fantastical idea, it did correlate to Weatherbee SD et al. 2006, in which the development of the bat patagium has been noted as rather atypical, developing first the specialised cheiropatagium and latter the rest of the patagia, inconsistent with the development in other gliding mammals but certainly on par with fluttering as means to develop the wing.

Later, Padian et al. 2013 dismissed the idea of cave-dwellers, but the emphasis on the hypothesis that early bats fluttered instead of gliding remained. In this scenario, creatures like Onychonycteris see themselves in a more plausible scenario: as arboreal mammals that weren’t that different from modern gliding mammals, but that flapped their arms to control their fall rather than simply letting themselves fall with style. Combined with the impetus to capture aerial prey, the drive to develop large, webbed hands occured, and subsequently it would only be a matter of time until true flight emerged.

This hypothesis, while so far only barely supported, certainly explains why bats achieved what no other mammal managed in a such a short amount of time. If it is a correct accessment, it defenitely parts mammalian flight from mammalian gliding, relying on the presence of arm movement since it’s very earliest stages, something that by itself is very rare among parachuting mammals. This also explains why bats managed to achieve profecient aerial hawking early on when birds and pterosaurs seemingly only developed it much later, having evolved from day on to snare aerial prey.

What Birds Tell Us

RPR illustrated (author unknown; I desire clarification so I can give the proper credit)
RPR illustrated (author unknown; I desire clarification so I can give the proper credit)

How avian flight developed has been one of the most debated topics in paleontology across it’s existence as a discipline. You’ve all heard about gliding, about running and beating the wings like a manic, WAIR, et cetera.

At this moment in time, the debate is still long from settled, but it seems that a few options can be safely struck down as unlikely. The running hypothesis, for example, has never witnessed much support, and nowadays it is rarely defended outside of conjunction with WAIR; the fact that most known early paravians had hindwings also renders this possibility unlikely.

With Dyke, G., de Kat, R., Palmer, C., van der Kindere, J., Naish, D. & Ganapathisubramani, B. 2013, gliding should also be out of the picture: the most famous supposed glider, Microraptor, was appearently a really lousy aeronaut, ill suited for long distance gliding. Therefore, as with bats, avian flight was not derived from gliding, and the theropods that rose into the skies did so in methods equally as active as their chiropteran successors, by flapping their wings.

Thankfully, there is a menagerie of ideas about how birds flapped their way into true volancy:

Wing Assisted Incline Running (W.A.I.R.), in which dinosaurs runned up trees by flapping their arms, like modern terrestrial birds;

The Leaping Grapple, in which dinosaurs leaped at their prey, using the forelimbs to generate power to elevate themselves.

– RPR, or “ripper”, in which dinosaurs flapped their forelimbs to retain balance when eating their prey, much like modern raptors.

Of these, WAIR has gone under the most scrutiny due to the assumption that non-ornithothorace paravians could not provide enough of a vertical stroke in order to produce WAIR. Ignoring several examples in which this it has been argued that early paravians could provide vertical strokes, Holtz argues that a vertical stroke isn’t necessary to generate WAIR (https://www.facebook.com/thomas.holtz/posts/173481572740497), so WAIR is within the realm of possibilities. However, the fact that WAIR is only observed in Neognathae, with no evidence among living palaeognaths, may cast suspicion into it’s veracity.

The other two suggestions are reliant on the assumption that early paravians were predatory, an assumption progressively considered less plausible given the extensive evidence of omnivory in paravians like troodontids, oviraptorans and microraptorids. Likewise, forms suspected of using these, like eudromaeosaurs, were presumably too large and specialised to be ancestral to birds. However, it is very likely that similar processes, unrelated to predation, were what developed dinosaur arms into avian wings.

Regardless of the method, it appears that exaptations for flight occured very early in theropod evolution, as the evidence of scutes in Concavenator implicates the presence of hindwings in non-coelurosaur theropods.

What Pterosaurs Tell Us

A series of Hypothetical Pterosaur Ancestors (HYPTAS) by Maija Karala (Eurwentala), in turn inspired by Mark Witton's own HYPTAS.
A series of Hypothetical Pterosaur Ancestors (HYPTAS) by Maija Karala (Eurwentala), in turn inspired by Mark Witton’s own HYPTAS.

Currently, pterosaurian origins are sorrounded in mystery. The most accepted hypothesis is that they’re sister taxa with Dinosauromorpha, and are especially closely related to the small archosaur known as Scleromochlus, though even this tells us very little about the hypothetical pterosaur ancestors, given the morphological diversity of early avemetatarsalians. If we go by animals like Scleromochlus, we find ourselves in an interesting position: while pterosaurs are quadrupedal animals with powerful forelimbs and plantigrade hindlimbs, Scleromochlus is a bipedal animal with long, digitigrade hindlimbs and small forelimbs. In the 90’s, this wouldn’t have been something hard to invision, but now that we know pterosaurs quadrupedally launched and were generally happy running on all fours, it seems very bizarre indeed.

Scleromochlus does not seem like a gliding animal, to say the least, and although basal pterosaurs suggest an arboreal ancestry, gliding is not necessarily on the equation. A suggestion posited by David Peters (I know, but this doesn’t involve squamates, so it’s okay) is that the key of the pterosaurian wing, the massive fourth finger, evolved as a display device, which would make sense in these original bipedal runners, with the forelimbs free to occupy other functions. With time, these display devices would have become larger and more elaborate, and eventually be useful in WAIR or fluttering. Eventually, once the wing was large enough, flight would have become possible, and subsequently the animals would have shifted to quadrupedality as the wing membranes connected the limbs. This hypothesis would also explain the elongated fifth toe, which would have also evolved as a display device, before becoming an effective support for the cruropatagium.

As of this writting, the fog sorrounding pterosaurian origins is still thick, and therefore one can only imagine how these animals first took to the sky.

Conclusions

Based on birds and bats, as well as modern gliders, gliding appears to be effectively independent from flight, gliding animals seemingly unable to produce powered flight and animals that have evolved powered flight having developed it in unusual circumstances. Exceptions might exist, including possibly pterosaurs, but as it stands vertebrate flight has only been able to evolve from behaviours that prommote forelimb movement, with aerodynamic speciation not leading at all to volancy.

Bakonydraco was a tapejarid like azhdarchid… or an actual tapejarid

Bakonydraco galaczi by Sergei Krasovskiy, in conflict with the ceratopsian Ajkaceratops.
Bakonydraco galaczi by Sergei Krasovskiy, in conflict with the ceratopsian Ajkaceratops.

Bakonydraco galaczi is a very odd pterosaur. Known primarily from a single, yet extraordinarily well preserved mandible from the Santonian-aged Csehbánya Formation of Hungary’s Bakony Mountains (as well as associated forelimb bones and neck vertebrae that most likely belong to it), Bakonydraco is part of a strange insular assemblage of animals that also include several types of dwarf ornithischian dinosaurs (including Ajkaceratops, the first european ceratopsian to be discovered) and abelisaurs, the undetermined paravian Pneumatoraptor and the freshwater mosasaur Pannoniasaurus, as well as a variety of terrestrial and alligatoroid crocodylomorphs, albanerpetontids, fish, turtles, enantiornithes and varanoid lizards. With azhdarchid pterosaurs also known from the formation, and living in a time period where the only other significantly represented clade of toothless pterosaurs were the marine pteranodontians, Bakonydraco‘s subsequent classification as an azhdarchid was rather predictable, but since day one that this animal was considered very odd by the standards of it’s clade.

The holotype, MTM Gyn/3
The holotype, MTM Gyn/3

Bakonydraco<'s most distinctive characteristic is it's mandibular symphysis, which is quite aptly described as "spear-like". Vertically tall at the base both on the upper surface and on the underside, forming a sharp "cone", bearing a posterodorsal curvature and notoriously made distinct from the rest of the jaw by a transverse ridge – which could implicate the end of the lower jaw rhamphotheca in the live animal -, it seems like the logical extreme of the "short rostrum" azhdarchid jaw model, trading the longer stork-like beak for a shorter pecking weapon; other azhdarchids with short rostrums include the Javelina Formation azhdarchid and Hatzegopteryx, though no other azhdarchid shows such extreme changes in the mandible symphysis morphology.

The original paper describing the specimen compared this mandible morphology to that of tapejarid pterosaurs, specifically Tapejara proper and Sinopterus, which also possess similar short, dystally deep lower jaw symphysis. In particular, the jaw is most similar to Tapejara‘s, only differing significantly in that the depth in the symphysis’ base has evolved into a full blown ventral crest in Tapejara, and that the shared posterodorsal ridge at the anterior dorsal surface of the symphysis is blunt in Bakonydraco but not in Tapejara. Sinopterus lacks the transverse ridge and the posterodorsal curvature common to both animals; if the three composed a clade of closely related species, one could argue that Sinopterus would be the most conservative member and Tapejara the most specialised, with Bakonydraco somewhere in the middle.

Indeed, this comparision between tapejarids and Bakonydraco went as far as the initial lifestyle proposition: Atilla Ösi et al. proposed that Bakonydraco was a frugivorous animal in the same vein as often theorised for tapejarids, citing the theoretical gap of the closed jaws as ideal for grabbing fruits and leaves, though it notes that the animal’s size would have limited quadrupedal climbing and arboreal motion, forcing the animal to either forage on forests with spaceous branches, or walk around in the ground and browse from shrubs and low trees. While the paper does argue in favour of piscivory due to then accepted notions of all pterosaurs being mutant seagulls, the fact that azhdarchids are now known to have been terrestrial foragers makes Ösi’s hypothesis of an okapi-like Bakonydraco grabbing fruits and leaves from shrubs as it walks past them the more likely explanation, an exceptionally accurate prediction that Witton 2008 was dutiful to notice. Most importantly, tapejarids have also been understood to be terrestrial foragers as well, their tree climbing capacities being only marginally better than those of other azhdarchoids (as adults, at least), so frugivory in these animals would also have been obtained via browsing.

Thus, it is fairly reasonable to consider Bakonydraco a particularly strong case of convergent evolution, an azhdarchid occupying or evolving towards occupying a similar ecological niche to that of the earlier tapejarid pterosaurs, presumably filling vacant niches. The idea that Late Cretaceous azhdarchids moved into ecological niches previously occupied by other pterosaurs, is nothing new, as with the case of the rather thalassodromedid like Javelina azhdarchid – and perhaps even the gigantic Hatzegopteryx, whose adaptations for macropredation seem very similar to those of Thalassodromeus itself -, and indeed the Late Cretaceous predominance of these pterosaurs may represent a systematic radiation in response to the absence of other azhdarchoids. Since the examples offered are “short snouted” azhdarchids, it should perhaps be of interest to examine the diversity of these azhdarchids before the post-Turonian Late Cretaceous.

Then again, maybe not….

Pterosaur phylogeny according to Pterosaur phylogeny according to Andres, B. & Myers, T.S. 2013 (the red oval is my creation)
Pterosaur phylogeny according to Pterosaur phylogeny according to Andres, B. & Myers, T.S. 2013 (the red oval is my creation)

More recently, Andres, B. & Myers, T.S. 2013 argued that the convergence between Bakonydraco and tapejarids was a tad too extreme to have aroused independently, and that Bakonydraco actually is a tapejarid, a fairly derived one that is non-surprisingly the sister taxa of the Tapejara + Tupandactylus clade, with “Huaxiapterus” being the closest relatives outside of this clade (“Huaxiapterus” in this cladogram is considered to be paraphyletic, with H. benxiensis being closer than H. corollatus). This analysis makes full use of the character list and matrix dictated in previous pterosaur phylogeny tests, thus accurately pin pointing the number of characteristics that exclude Bakonydraco as an azhdarchid and showcasing the higher number of traits it has in common with tapejarid pterosaurs.

If this accessment is correct, then it means that Bakonydraco is not yet another type of azhdarchid, but an actual Santonian representative of Tapejaridae and thus of non-Azhdarchidae Azhdarchoidea, thus being not only more evidence of Late Cretaceous pterosaur diversity outside of Azhdarchidae, but also that Late Cretaceous azhdarchid radiation was independent from the “decline” of other azhdarchoid pterosaurs (except maybe thalassodromedids), that Tapejaridae existed as a ghost lineage for at least 16 million years, and that tapejarids could reach grander sizes than previously thought (Bakonydraco is speculated to have had a wingspan of 4 meters [based on azhdarchid proportions; tapejarids had proportionally slightly longer wings], while the largest unambiguous tapejarids had wingspans of around 2.9 meters; it was certainly much taller and heavier as well, since these animals were largely terrestrial pterosaurs with proportionally short wings).

If Bakonydraco was a tapejarid, then it might be expected that these pterosaurs retained the cosmopolitian presence that they had in the Lower Cretaceous, and that their general absence in the Late Cretaceous is correlated to a poorer fossil reccord and the absence of konservat-lagerstattën dating to this epoch. However, it could also be that the clade did indeed systematically disappear from most of the world, and that insular forms like Bakonydraco would have been all that was left of Tapejaridae by the Santonian; given the presence of other “relictual species” on the Csehbánya Formation, such as Pannoniasaurus, this definitely has some precedence. With no remains known from anywhere else in Europe, Bakonydraco galaczi was almost certainly an endemic species to the island that is now Hungary, and given it’s massive size compared to those of it’s relatives it would have been a blatant case of insular gigantism, while the dinosaurs it co-existed with were island dwarfs. Based on the inferred body proportions, it would have been one of the island’s tallest browsers, competing only with the local species of Rhabdodon for the leaves and fruits of it’s forest habitat. Bakonydraco might had even been the flightless pterosaur many look after, Cretaceous’ non-avian Aepyornis, though the presence of abelisaurs and a possible tetanuran would probably make this unlikely, and I am doubtful if pterosaurian flightlessness would have ever evolved anyway.

Whereas a tapejarid or an azhdarchid strongly convergent on one, Bakonydraco was a very unusual pterosaur, certainly one of the strangest cases of Mesozoic insular megafauna.

REFS

Ösi, Attila; Weishampel, David B.; and Jianu, Coralia M. (2005). “First evidence of azhdarchid pterosaurs from the Late Cretaceous of Hungary” (PDF). Acta Palaeontologica Polonica 50 (4): 777–787. Retrieved 2009-07-28.

Andres, B.; Myers, T. S. (2013). “Lone Star Pterosaurs”. Earth and Environmental Science Transactions of the Royal Society of Edinburgh

Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.

Largest non-pterodactyloids

The largest non-pterodactyloid pterosaurs are the scaphognathines Harpactognathus and Cacibupteryx at wingspans of 2.5+ meters, with the wukongopterid Cuspicephalus and some rhamphorhynchines at wingspans of 2 meters. I was under the impresson Campylognathoides beated both at a 3 meter wingspan, but as it stands it is bogus, having it’s wingspan lowered at 1.9 meters.

I find it interesting that, according to Habib, this is around the same size limit as the largest theoretical bats, which could go on to around a 3 meter wingspan. It is possible that the largest non-pterodactyloid pterosaurs, with their clumsy terrestrial gait and without sophisticated adaptations for quadrupedal launching, and possibly with a rather rudimentary pulmonary air sac system, were bound by the same constraints as bats, being unable to launch properly from flat surfaces and to supply enough aerobic respiration derived energy for taking off at large weights. It’s no surprise that the largest of these pterosaurs were all thought to have been arboreal animals from terrestrial settings, just like modern flying foxes, albeit presumably not analogous in terms of lifestyle.

The Speculative Dinosaur Project: Azhdarchidae

Once delegated to comments on their size and occasional mentions in
non-professional literature, azhdarchids have since become one of the most
iconic lineages of pterosaurs. Well adapted to terrestrial locomotion and being
the first pterosaurs where this trait was discovered, azhdarchids have become a
window to the true nature of pterosaur diversity, not as aberrant fish eating
gliders as once thought, but as generalistic and diverse animals not unlike
terrestrial birds, some of which possibly even competing with predatory
dinosaurs. Azhdarchidae was one of the most successful and long lived lineages
of pterosaurs: at a timespan of 80 million years, azhdarchids lived almost
through half of the entire Mesozoic, and were only killed off because of the
catastrophic KT event.

Naturally, in Spec, the 80 million years had to them added another 66 million
years, but this wasn’t appearent at first. For some inexplicable reason, early
spexplorations did not found pterosaurs, returning instead simply with a
Palaeocene age skull found in a Pacific Northwest shore; this skull, named
Gigantala cranitus, was for a while thought to be the last of Spec’s
Pterosauria. However, posterior investigations found flocks of azhdarchs across
the world’s plains, and even more careful and extensive research revealed
several other types of pterosaur. While pterosaur faunas are often more subtle
than dinosaur or even mammalian faunas, azhdarchs at least are an important
component in tetrapod biotas in most landmasses, in some cases even accounting
for as much as a third of the present megafaunal biomass, and being quite
visible. It has been suspected that, for some reason, the first spexplorers
ignored or ommited pterosaurs from their research, but for the moment Hanlon’s
Razor is applied.

HISTORY

Azhdarchs first appeared in the Lower Cretaceous, quite possibly as far back in
time as the Jurassic/Cretaceous boundary with forms like †Palaeocursornis
showing unambiguous azhdarchid material from this era. Part of Azhdarchoidea, a
clade of toothless, terrestrial omnivorous pterosaurs, azhdarchs were fairly low
key during the Lower Cretaceous, even overshadowed by some of their relatives,
such as the bizarrely-crested tapejarids or the macropredatorial
thalassodromedids, increasing somewhat in diversity in the early Late Cretaceous
as their relatives dwindled. However, it was after the Turonian where azhdarchs
got their chance to shine: in an evolutionary blink of an eye, they dominate the
world’s pterosaur faunas, far outnumbering all other forms in terms of preserved
remains. More so, they also showcase some degree of diversity and
specialisation, with different jaw shapes (most common being a dichotomy between
forms with long, curved bills and forms with short, spear like beaks), different
degrees of neck elongation, and most impressively bigger sizes: azhdarchids
produced the largest flying animals ever known, with the titanic giraffe-sized
Quetzalcoatlus being the most iconic example. In HE, their story ends right
in their golden age, as the KT event killed azhdarchs as they underwent their
radiation, but in Spec it obviously progressed.

In Spec’s Palaeocene, the most studied pterosaur is the former “Spec’s last
pterosaur”, †Gigantala. Remains of this pterosaur are best known from rock
formations in western Canada, though the animal is found across North America,
and possibly other Laurasian landmasses as well. Two species are recognised,
Gigantala cranitus and †Gigantala hastarostris, the former being by far the
most common and well studied. †Gigantala cranitus is a mid-sized azhdarch,
with a wingspan of 4.5 meters, while †Gigantala hastarostris was seemingly
larger at an estimated 7 meters; the former occurs throught the Palaeocene,
while the latter is restricted to Selandian deposits. †Gigantala is unique
among azhdarchids for it’s short neck, having reversed the elongation and
flatenning of the azhdarch cervical vertebrae to the condition seen in earlier
azhdarchoids like chaoyangopterids. With long jaws, typical limb proportions for
neoazhdarchians and their normal bias towards inland terrestrial settings,
Gigantala was most likely a generalistic carnivore, perhaps akin to
thalassodromedis in habits. The skull doesn’t seem to show much deviation from
normal azhdarchid skulls except for it’s abnormally small nasoantorbital; †G.
cranitus
has a longer, stork-like bill, while †G. hastarostris has a shorter
beak with scizzor-like jaw edges.

Gigantala disappears from the fossil reccord in the Eocene, the youngest
fossils dating to two million years before the PTM. However,
other pterosaurs explode in diversity in an event at times called “Cenozoic
Pterosaur Renaissance” (CPR), and among these we see several types of
azhdarchids, diversified as very unusual and bizarre forms that deviate from the
“stork-like” norm. Among these are the limuazhdarchines, a lineage of small
azhdarchids with long, wide webbed toes, seemingly converging ecologically with
the long gone ctenochasmatoids; †Heusia, a diminutive azhdarchid with a
wingspan beneath a meter that may show adaptations for aerial foraging; and
Verpacheirus, a lanky, sloth like azhdarchid. Giant azhdarchids are rare,
presumably due to the spread of global forests, though remains belonging to
animals with a presumed ten meter wingspan are known from China, Morocco and
Australia; otherwise, the largest forms seem to be beneath a wingspan of 4
meters.

With the Oligocene, most of the more bizarre forms disappear from the fossil
reccord – though this could be due to limitations in the availiable fossil
reccord, as Spec palaeontology is still a new field -, returning to a normal
dominance of longer legged plains-dwellers, some of which returning to giant
sizes – one species, †Aetiogenoi eletherios, is quite possibly the largest
flying animal ever known, with a wingspan of 15 meters; at an estimated weight
of 500 kilos, it may very well had reached the limit of azhdarchid flight
capacity. The Miocene remains most of the same, though with an increase in
morphological diversity. The Pliocene and Pleistocene see a mild weeding out of
their diversity, but the survivors quickly exploit the vast grassland world that
has formed, and become an important component on grassland ecosystems, though
sacrificing most of their inovation in favour of conservatism.

BIOLOGY

Azhdarchids are among some of the most derived pterosaurs, having taken the
“aberrant” pterodactyloid traits to their extreme, yet ironically also fairly
conservative. Following the lophocratian tendency for terrestriality,
azhdarchids have long, powerful hindlimbs, hatchet-shaped postacetabular
processes and very long fourth metacarpals – the forelimb elements being
proportionally comparable to those of fast running ungulates, and having the
longest fourth metacarpals among pterosaurs. They are efficient walkers and
runners, even being suberb gallopers, being some of the most terrestriality
adapted pterosaurs ever known. Their feet are generally short and narrow, yet
quite strong, being of poor use to swim or even to wade, but proper for
galloping and, in some forms, for climbing, having developed strong claws. They
have rather mammal-like footpads, covered with scales.

While terrestrial, azhdarchids in general also display several further
adaptations for powered flight. Up to 50 kilos of robust flight musculature are
anchored to their shoulders, attached to large, robust scapulae and coracoids of
subequal length, large glenoids and anterior cervicals bound into a notarium,
and attaching to the humeri in large, though fairly simple dectopectoral crests.
The rather large, blocki humeri have a large pneumatic opening in their proximal
anterior surface, to which air sacs are attached: like ornithocheiroids and
other neoazhdarchians, azhdarchids have extended their pulmonary air sac system
into the patagia, the propatagium being completly inflatable and the
brachiopatagium being pneumatised along the forelimb, allowing the animal to
save weight as well as to help the muscle fibers and the pteroid to manipulate
the shape of the wing membranes.

While the fourth metacarpal is predictably very long and robust, the metacarpals
supporting the smaller, clawed fingers are much smaller and locked entirely at
the end of the fourth metacarpal, having lost their connection to the wrist
bones, a feature also seen in other neoazhdarchians and some ornithocheiroids.
The wing finger is the smallest by pterosaurian standards, usually 47% of the
overall wing length. The first phallange is the longest, while the second and
third phallanges have a T-shaped cross-section that reinforce the torsional
motions of the dystal part of the wing during flight.

With the short, curved wing finger and long metacarpal, the wing has normally a
rather characteristic low aspect ratio, as to be expected from flyers in
terrestrial settings; however, much like other pterosaurs, azhdarchids can
contract their wing membranes, increasing their wing loading. While large flying
birds like rocs are soarers, azhdarchids are better described as flap-gliders,
something facilitated by the very energy economic pterosaurian launching and the
shape-changing wing membranes. With just a couple of wing strokes, azhdarchids
can cover very large distances, and with the largest forms being able to cover
as much as 16,000 km in a single, non-interrupted flight, geographical barriers
mean very little for the larger animals.

Azhdarchids have proportionally the longest necks of all pterosaurs, and perhaps
the longest in porportion to the body size of all known vertebrates and the
longest necks outside of Sauropoda, period, achieved through the elongation of
the cervicals three to eight, with the fifth characteristically stretched to a
length eight times it’s width. Flattened and with reduced neural spines, their
vertebrae have an unique tubular appearence, rather apropriate considering their
pneumatisation; due to their sheer length, it was thought that azhdarchid necks
were rather inflexible, and indeed the tubular central neck vertebrae allow
little motion, but the vertebrae at each end of the neck allow a wide range of
motion. Like most pterosaurs, azhdarchids have rather elastic neck tissues, and
can expand their easophagi considerably, allowing them to contain proportionally
very large prey. As the azhdarchid torso is rather small, the animals often just
store their prey in the neck, not needing a gular pouch, where the trapped prey
item will stay as it moves downwards, being digested and processed slowly.

Azhdarchid skulls tend to be proportionally very large, the extinct
Aetiogenoi eletherios holding the reccord for the longest skull on a
terrestrial animal at 6 meters from jaw tip to the back of the skull. The
nasoantorbital, the fusion of the nostril and the antorbital fenestra so
characteristic for pterodactyloids, is rather large, sometimes longer than the
torso, and extends above the eye, a trait only seen in other azhdarchoids;
uniquely, the premaxillary bar starts out thin and becomes rapidly thick more
dystally, while in other azhdarchoids it runs in a subparallel fashion. As with all
azhdarchoids, teeth have been lost altogether, being replaced by a rhamphotheca
sheet that covers most of the jaws, connecting the beak to the crest in the
skull. Azhdarchid crests follow the two pterosaur crest models: either a bony
casque, or a mainly keratinous crest supported by fibrous bone.

Generally social animals, azhdarchids can often be seen in large flocks.
Azhdarchids have proportionally small brains, but displaying an astonishing
level of complexity, which translates to problem solving skills. For the moment,
no detailed study on pterosaur intelligence has been made, but some researchers
have compared azhdarchid social behaviours to those of elphabas, Spec’s weird
flying primates.

DIVERSITY

HASTAZDARCHINAE

Hastazdarchines are common denizens on the world’s grasslands, and the most
diverse and successful of modern azhdarchids, large flocks being observed across
the world’s open spaces. Hastazhdarchines follow the classic “short jawed
model”, with their rostrums being spear-like and often deep. They have
keratinous crests, often without a bony crest underneath, in some species
falling off after the breeding season. Their claws are small and hoof-like,
being of little use for climbing. Ovovivipary is common in these animals, and
seems to have evolved and possibly even been lost (and redeveloped) multiple
times.

Hastazdarchines seem to have diverged from their closest relatives in the
Miocene, and indeed the oldest remains known so far are from the earliest
Pliocene. More so than other azhdarchids they seem to have enjoyed the global
cooling, their ovoviviparous tendencies allowing them to cope better with colder
environments than other pterosaurs, not having the restrictions laid out by
having to bury their eggs, as well as ensuring a higher clutch survival rate
without sacrificing mobility. This is particularly evident in relation to plains
dwelling birds like the palaeognath bastards, which need to built nests and
incubate their eggs, leaving them vulnerable. It does add detrimental weight to
the animal, but this is lessened out by the animals’ energy saving launching and
relatively small young.

Purple Azhdarch (Hastazhdarcho purpurea)

The Purple Azhdarch occurs throught the plains of the Old World, frequenting the
steppes of Eurasia from Central Europe to Siberia during Spring and Summer
months, and wintering as far south as Tanzania during Winter, with many areas of
it’s range supporting sedentary animals, such as South Africa. With a wingspan
of 5 meters, it overshadows the largest rocs and gorgeese it co-exists with,
with only the Rukh competing with it in terms of size, though still leagues
beneath the largest living pterosaurs. Like most azhdarchids, it spends most of
it’s time on the ground, where it forages and rests, though it still flies
frequently even as sedentary animals, be it for move around quicker, seeking new
feeding or resting spots, evading predators when physical violence or galloping
doesn’t work, or simply for the hell of it. The Purple Azhdarch is mostly
coloured in light and golden shades of brown, with violet markings of various
shapes along it’s back, achieved thanks to unique porphyrins. The face is also
violet, with the headcrest being of a deep indigo. The beak is of a normal brown
colour, while the limbs have whiteish, unpigmented coats, and the dorsal part of
the wing membrane has a dark colour.

The Purple Azhdarch is a rather generalistic omnivore. The bulk of it’s diet is
composed of mammals, squamates, dinosaurs (particularly birds, small oviraptors,
jackalopes and mattiraptors), large insects, eggs, berries, fruits, soft plants
and seeds. Food, animal or plant, is generally ingested alive, the typical thick
sauropsid
easophagus walls rendering most claws, teeth and beaks useless to fight with,
though some prey like poisonous squamates or animals with horns may be grabbed
by the beaked jaws and are either suffocated or have their heads beaten against
a hard object for as long as it takes, an activity hastazhdarchines are
particularly suited to do thanks to their shorter and deeper jaws. Subduing
large prey is harder, but a Purple Azhdarch has been reccorded to capture a
cheetaur, managing to suffocate it long enough for it to be too weak to fight
back. The pterosaurs may also attempt to capture birds and other flying animals
on the wing, particularly during migrations. Purple Azhdarchs often forage in
the company of ungulipedes and other large herbivores, whose tolerance for the
pterosaurs may decrease when they have young.

Purple Azhdarchs usually gather in large flocks, which thin out when the animals
forage during the day, the animals walking away from the congregation as they
wander around in search of food. During the breeding season, both sexes try to
impress mates by raising their heads and emitting characteristic roars that may
echo for miles. There is little sexual dimorphism, as interspecific competition
for mates occurs in both males and females, an elaborate set of “mating groups”
forming, that may either be polygynous, polyandrous or somewhere in between.
These groups remain together for most of the breeding season, sleeping and
foraging together, and seem to be a measure of protection for gravid female/s.
Pregnancy lasts for about 2 months, the female/s then giving birth. They soon
hatch, and forage around the adults, often eating insects disturbed when the
adults forage. They grow rapidly for the first two years of their lives,
reaching 53% of the adult size by sexual maturity, speanding another five
growing slowly until they reach their maximum size.

Hesper Azhdarch (Hastazhdarcho zephyrus)

A smaller cousin of the Purple Azhdarch, the Hesper Azhdarch has an average
wingspan of 3.5 meters. It occurs across North America’s open habitats, being
some of the most common continental flyers in the landmass at flocks of
thousands. It’s pelage is large composed of various tones of gray, leaning
towards white, with a black head and a red headcrest. While typically
opportunistic, it has a prefference for grasshopers and similar large insects,
their breeding seasons often coinciding with the arthropods’. While the massive
flocks may branch out during foraging, it is very rare to see an animal alone,
being vulnerable to larger azhdarchids and avisaurs. Juveniles often perch on
the backs of hmungos and other large plains dwellers, though they scarcely
behave like oxpeckers, only paying attention to the largest ticks.

Yhi (Hastazhdarcho deserti)

One of the only two hastazhdarchines endemic to Australia, the Yhi sticks out
like a sore thumb in a land of more bizarre pterosaurs. With a bright gold
pelage, orange wing membranes and a white headcrest, the Yhi strides the
outback, unbothered by the hot australian Sun. It feeds on more plant matter
than most other hastazhdarchines, being an important distributor of several
fruits and seeds in the scrubland; however, like all azhdarchids, the Yhi is a
hazard to animals as large as the average tingamarroid. The Yhi frequently rests
atop the outback’s strange mountain rocks like the Uluru, wandering across the
crags like alien mountain goats, though it is more than happy to rest in the
lowlands. Unlike the rest of *Hastazhdarcho*, it is fully oviparous, the female
laying eggs in a secluded mound, tended by her and her mate for 3 months, before
the flaplings emerge and leave, a trait that seems to have evolved secondarily
as it’s closest relatives are ovoviviparous.

Partridge Azhdarch (Hastazhdarcho xenoperdix)

The Partridge Azhdarch is one of the smallest living azhdarchids at a wingspan
of just 80 centimeters. Residing across the Levant and the Mediterranean, this
animal bears a cryptic colouration of various browns and grays, as opposed to
the more vibrant colouration of it’s larger relatives. During migration, it
gathers in large flocks, but it is otherwise solitary, only gathering in pairs
during the breeding season. Although it has a similar omnivorous diet, it
co-exists with several species of streks and bastards, often feeding on them as
well.

Condor Azhdarch (Vulturazhdarcho sudamericanum)

Preffering alpine grasslands and other open highland biomes, the Condor Azhdarch
is nonetheless happy to occur in lowlands with frequency: it ranges across most
of western America, from the middle of the Rockies’ range well into the chilean
Andes, soaring over the mountains with a four meter wingspan. It has a rather
short neck with block-like neck vertebrae, similar to those of thalassodromedids
except with the typical azhdarchid lack of neural spines, rendering the neck
more flexible than that of most other azhdarchids. Combined with it’s jaw tips
being compressed into sharpened edges, the Condor Azhdarch is better suited to
deal with proportionally large prey, wrestling commonly with viriosaurs and
other notosuchians, bastardsloths and juvenile hadrosaurs and therizinosaurs,
using the beak to bite off chunks of flesh and to bite the throat to suffocate
the victim. Regardless, most of it’s prey are still small animals, and it also
frequently scavenges, often intimidating all but the largest harpies away from
corpses.

Coloured mostly in black, with silver wing membranes and a gray-purpleish head –
still covered with pycnofibrils, having no thermoregulatory use for a naked head
thanks to the wing membranes as with all pterosaurs -, this pterosaur showcases
perfect sexual dimorphism, with the male having a large headcrest, coloured in
red alongside the beak, while the female has no crest and has the beak coloured
in black. Males are more sedentary than females, keeping large territories while
females fly around. Males may tolerate other males within their territory, but a
clear pecking order is formed, with the dominant male always feeding first,
either at normal carcasses or at kills performed by other pterosaurs within the
territory, with other males and females feeding afterwards; only small prey are
not regulated in this way, as they are instantly swallowed anyway. Females give
birth to live young, the flaplings following her around, often feeding from her
kills or on carcasses she feeds at. Juveniles between birth and two years of age
seem to be exempt from the feeding hierarchy, though they sheldom aproach a
non-occupied dominant male, lest he eat them instead.

Tohil (Tohilus aviserpens)

The Tohil is the second largest flying animal alive and the largest of the
hastazhdarchines at a wingspan of 9 meters, and towering above four meters on
the ground. True to the capacities of giant azhdarchids, it is found on nearly
every landmass except remote oceanic islands and Antarctica – though it may
occur as a vagrant in either -, occuring in grasslands from as far away as the
american midwest as to New Zealand’s highland moors; it is an efficient flying
animal, managing to remain an efficient flapper at large sizes, and only
impeeded by wide oceanic expanses, where the absence of thermals make the
animals reluctant to go much further. Predictably, the Tohil have a diverse
diet, feeding on a variety of animal species as well as browsing frequently,
swallowing fruits and leaves like a pterosaurian giraffe. The male bears a deep
black pelt, with gray and white bands around the shoulders and extending midway
into the throat, a bright yellow beak and a bright crimson crest with an
eye-like dot in it, while the female is of a simple gray, with a brown beak.
Tohils, being cosmopolitian animals, breed year round, often flying large
distances in search of a viable partner. Gravid females can still fly and are
not significantly impaired, though they spend more time on the ground when not
foraging. Tohils reach their sexual maturity at around 7 years of age.

Rhea Azhdarch (Tohilus minor)

In contrast with it’s closest relative, the Rhea Azhdarch has a wingspan of just
two meters. It occurs widely across South America’s open environments, north and
south of the Amazon. Coloured mostly in various shades of gray, with black bands
in the shoulders and neck and a black beak, the Rhea Azhdarch is a frequent
companion of the flocks of nandrakes that roam the continent’s grasslands. Both
animals have similar diets, though the Rhea Azhdarch is more carnivorous,
feeding on snakes and small notosuchians with frequency. It is a rather
crepuscular animal, and it is occaisonally active at night.

BUCEROSAURINAE

Bucerosaurines are in some ways basically the opposite of hastazhdarchines:
their jaws are long, slender and often surved, and their crests are bony casques
without keratin extensions, earning them designations such as “hornbill
pterosaurs”. Their claws also tend to be larger and quite curved, allowing them
to climb trees, hanging upside down like sloths (like other pterosaurs, the
ungrasping feet don’t allow for bat like suspension). Bucerosaurines first
appear in the fossil reccord in the Eocene, and seem to have had a lot of global
success during the Oligocene and Miocene, bing seemingly the dominant
azhdarchids during the latter, before being largely replaced by hastazhdarchines
in the Pliocene, reduced to the genus *Bucerosaurus*. Nonetheless, a number of
species still remain, one of which Spec’s largest flying vertebrate.

Golden Calahao (Bucerosaurus magnificens)

The Golden Calahao is a common denizen of the tropical rainforests of Asia. At a
mere wingspan of 3 meters, it is nonetheless one of the largest rainforest
residents, overshadowing all but the largest birds and elphabas. The Calahao
retains the usual azhdarchid limb proportions, but while it frequently descends
from the canopy to feed on the forest foor, it spends most of it’s time hanging
upside down like a sloth, using it’s large and powerful claws to remain
suspended. It is faster than a sloth, however, and certainly more active than
the languours it shares the forest with: it is an omnivore, using the long
azhdarchid neck and jaws to snatch fruits or small animals while otherwise
standing still, allowing the Golden Calahao to forage cryptically, without being
detected by predator or prey. With it’s short and broad wings, it glides
effordlessly across the open canopies of the asian rainforests.

The male is larger, has a more radiant pelage and a larger casque. During the
breeding season, he builds a mound of vegetation amidst the branches or in a
large tree cavity, where females lay their eggs. He tends to this mound for
three months, removing or adding plant matter as to keep a constant temperature,
before the flaplings leave.

Kongamato (Bucerosaurus africanus)

A denizen of Africa’s tropical rainforests and swamps, the Kongamato is smaller
at a wingspan of 2.5 meters, and bears a dark gray pelage and wing membranes,
only the bright yellow or orange beak and casque standing out. It often descends
to forage at the water’s edge, having a prefference for aquatic snails and
crustaceans, usually grabbing them from the shore rather than wading.
Nonetheless, it is still mostly a frugivore, and through most of the time it is
hard to detect as it forages in the deep forest.

Australian Calahao (Bucerosaurus dorfi)

The Australian Calahao is larger than it’s eurasian cousins, reaching a five
meter wingspan. While capable of climbing trees – and outback rocks -, it spends
most of it’s time on the ground, foraging in a more traditional azhdarchid
manner, both on terrestrial prey and on fruits it browses from the trees; it
feeds on less hard plant matter than the local hastazhdarchines, and on less
animal prey than other local pterosaurs. It bears a distinctive white pelage
with pink wing membranes and a metallic black beak and casque. Uniquely among
calahaos, the male doesn’t take part in protecting the nest, females simply
laying their eggs on termite nests.

Giant Calahao (Bucerosaurus giganteus)

The largest living flying animal, the Giant Calahao reaches a wingspan of 13
meters and stands at six meters high; combined with the normal bucerosaurine
slender and long jaws, it almost seems like a time shifted Quetzalcoatlus,
albeit enlarged. Once thought to represent an older line of bucerosaurines,
genetic evidence lists it amidst the bucerosaurines, closest to the Australian
Calahao; the oldest remains date from the mid-Pleistocene, belong to a possible
palaeosubspecies that was smaller by a third.

With shorter claws than it’s smaller relatives, the Giant Calahao is a very
aerial animal, spending most of it’s non-roosting or non-foraging time flying.
It can be found anywhere on Earth, appearently unfettered to geographical
barriers: an individual lunching on monotremate pups in the Antarctic Peninsula
may tomorrow be flying over Tanzania. Not even the open sea deters it from
trasversing it, crossing the waters by flapping powerfully, covering miles in a
matter of minutes. Only colder temperatures discourage the Giant Calahao, and
even then the poles are rarely safe during Summer months.

While it feeds on fruits, the Giant Calahao is mostly a carnivore, using it’s
long jaws to snatch up animals as big as a human being from the ground. In some
areas it is the apex predator, by virtue of colonising remote islands where the
other large carnivores are either azhdarchids or avisaurs, and even in the
mainland it only fears the larger tyrannosaurs and abelisaurs, though draks,
rhynchoraptors and carnocursorines may very well bring down weak unhealthy
pterosaurs.

CARNOCURSORINAE

Carnocursorines are the apex of azhdarchid specialisation for terrestriality,
being the only pterosaurs to have lost flight altogether. Genetic analysis
indicate that these animals diverged from their relatives back in the
Cretaceous, and the unusual Eocene form known as †*Murgonocheirus* is
occasionally suspected to be closely related to these animals. The first
unambiguous carnocursorines appear in the Oligocene, already flightless, and the
Miocene sees the expansion of this group in Oz, from small omnivores to large
dromornithid-like herbivores, as well as the terrifying predators that still
stalk the continent.

Curnocursorines have modified their body greatly for both flightlessness and
cursoriality. The wing membranes have been completly lost, though the pneumacy
of these animals remains, the forelimbs still filled with air by pulmonary
airsacs. The hindlimbs have become digitigrade, an unique trait among
pterosaurs, allowing the animals to gallop very efficiently: their efficient
lungs, combined with the typical pterosaurian anaerobic power, allows them to
gain speed very quickly, and maintaining it for very long distances, being some
of the most efficient cursorial predators to have ever evolved. Some of the
muscle complexes that powered their ancestors’ wings still remain, allow the
forelimbs to provide extra power during their strides. The wing finger has been
further reduced, and has develop a keratin coating akin to a claw, functioning
as a dagger either for defense against larger predators or to help subdue prey.
The hand fingers have enlarged, though the metacarpals are still small and
located at the end of the fourth metacarpal.

Without the need to remain relatively lightweight, the torso has been allowed to
expand, have body/proportions that are less skewed than in other azhdarchids,
most comparable to those of the extinct ctenochasmatoid pterosaurs. The tail has
also elongated, and in the more raptorial species it has become quite robust,
allowing the animals manouverabiity when chasing their prey.

All carnocursorines are viviparous, giving birth to live young through
placentas. The young animals still have membranes running along their forelimbs
and hindlimbs, using them to glide and in at least some cases flutter, being
latter absorbed by the animal as it grows. Specscientists have speculated that
these glides and flutters may give an idea about how pterosaurs got into the air
in the first place, and further study has been issued.


Marabou-Beak
(Leptoptilorhamphus mollusciphagus)

A denizen of the wetlands of northern Australia and southern New Guinea, the
Marabou-Beak wades while it’s distant flying relatives, the azhdarchids, preffer
the drier terrains. It’s beak is, as the
name implies, straight, long and deep, in terms of shape similar to that of
*Leptoptilos* storks, although with the obvious large nasanteorbital so
characteristic of pterodactyloids. The very base of the beak right above the
eyes produces a small pointed bony casque, of equal size in both genders. It is
about 2.5 meters tall, and it is usually coloured in soft gold with a black line
along the back and a black stripe branching from it that goes across the ear
opening and beneath the eye to the beak’s base.

With long webbed toes, this pterosaur spends most of it’s time wading in the
shallows, swimming very competently if it must. It feeds on pretty much any
unfortunate creature it can catch, as well as fruits and mushrooms, but it
preffers above all to feed on hard shelled molluscs such as bivalves and snails.
Here, the dagger-like wing finger comes in handy, prying open shells. It also
allows it to defend itself from the local rhynchoraptors and crocodilians of the
region.

Generally shy, these animals live alone or in small groups even during the
breeding season, though they are tolerant of other members of it’s species if
there is enough food. During the mating season, both genders produce long, deep
calls, often accompanied by infrasound vibrations similar to those of
cassowaries. Mating is a brief, poorly disputed affair, and the female is gravid
for three months or so, giving birth to seven to ten young that go seperate ways
afterwards.

Bill’s Bill (Cervociconia orodromaius)

The Bill’s Bill is endemic to the mountainous environments of Australia and
Tasmania. Isolated for several thousand years, these populations might be
significantly genetically distinct, though there are few anatomical differences,
if any. It is about 2 meters tall, and coloured in grayish-brown with dark brown
stripes on the neck and face.

This terrorsaur has a long, slender bill, with a very large nasanteorbital
fenestrae, reminiscient of those from it’s chaoyangopterid ancestors. It has a
very omnivorous diet, stopping short at complex plant tissue, but it has a
predilection for fungi and worms, using it’s sensitive beak to search for either
in the mud. Like it’s northern relative, it also has webbed toes, though nowhere
as long.

Having lost it’s wing finger, it relies exclusively on evasion to survive
attacks, often diving in deep water, which is usually near it’s foraging sites
anyways. It too is usually shy, rarely ocuring in groups above three
individuals.

Hyakarra (Carnocursor novaehollandiae)

The Hyakarra is the image most associated with terrorsaurs, being the most
common species on the continent. Standing at about 3 meters tall, it possess a
hooked tip on it’s beak, used to rip flesh as in predatory birds, while the neck
is proportionally short, with blocky neck vertebrae, as suited to deal with the
stresses of huntinger larger prey. It is usually white, to repell the intense
midday light.

Contrary to it’s marsh and forest dwelling relatives, and like other raptorial
carnocursorids, the Hyakarra’s hindfeet are quite narrow and not webbed, as
apropriate for acceleration based hunting. It hunts a wide variety of
Australia’s herbivorous dinosaurs, and even animals far larger than it are
targetted, the pterosaur ripping off chunks of flesh with the beak and/or
daggers, though obviously such feeding style is risky. It is not a pack hunter
per se, but it frequently overwhelms prey in loosely organised gangs, as other
predatory archosaurs do. Most of the time, however, it preffers to eat smaller
animals like tingamarroids.

It is among the most widespread of the terrorsaurs, ranging from southern New
Guinea to Tasmania. The only exception to their range is most of central and
western Australia, however.

Greater Terrorsaur (Carnocursor giganteus)

The largest of Australia’s predators is the massive Greater Terrorsaur, standing
at 4 meters tall. Like a larger version of the Hyakarra, it has a shorter and
deeper beak, reminiscient of phorusrhacid rostrums, capable of breaking bones.

Endemic to central and western Australia, the adults are the apex predators of
their ecosystem, rivalled only by the largest rhynchoraptors. They are less
specialised than their ornithopod competitors, however: while they are capable
of killing the largest herbivorous dinosaurs, they preffer to hunt smaller
herbivores. Most interesting is the niche partitioning between animals of the
same species: juveniles, being far more social animals, occupy a niche similar
to that of the Hyakarra, while the solitary adults preffer to scavenge the kills
of other predators. As such, the Hyakarra is less common in western and southern
Australia, where the Greater Terrorsaur is most dominant.

Pardic Terrorsaur (Carnocursor pardus)

A denizen of the forests of Papua New Guinea, the Pardic Terrorssaur is similar
in size to the Hyakarra, but bears a deeper and shorter beak like the Greater
Terrorsaur. Preffering the denser rainforests, little is known about this
animal’s more specific habits, though it appears to select proportionally large
prey.

AZHDARCHIDAE INCERTAE SEDIS

Dudu (Apteroazhdarcho novacaledonensis)

A rather strange animal, the Dudu is something of a mystery among pterosaur
researchers. Endemic to the islands of Melanesia, the Dudu is a seemingly
flightless azhdarchid, the adults bearing nothing but a thin brachiopatagium
running along the forelimbs, only significantly large in the wingfinger, serving
as a signalling device. However, juveniles not only have well developed
membranes, but can fly quite well, being able to traverse easy the distance
between islands, and begin to lose their ability to fly around the age of sexual
maturity, which may be surprisingly delayed if conditions aren’t apropriate.
Thus, the Dudu is not only well adapted to the volatile nature of island biomes,
but also unique among flying vertebrates for being volant in younger stages of
it’s life and flightless as an adult, a feature otherwise only observed in some
deinonychosaurs. The exact placement of the Dudu in the azhdarchid tree of life
is controversial, something not helped by odd atavisms like a long first
metacarpal that still connects to the wrist bones, though it is thought to be
closer to bucerosaurines.

The adult Dudu is a rather heavy, robust and overweight animal, a stark
departure from the gracile azhdarchid bodyplan, especially that of the
juveniles. With a large, deep beak, the Dudu is an omnivore, feeding primarily
on fruits, fungi and small animals of all types, even stealing eggs from the
dinosaurs it shares it’s habitat with like the Rath. It can best be described as
Melanesia’s answer to a hogbird or a vulgure.

Dupap (Melanoazhdarcho molluscivora)

The Dupap is a black and white azhdarch endemic to the Old World. With a three
meter wingspan, this animal is an unique specialist among azhdarchids, feeding
on molluscs and crustaceans it finds on the shoreline: like most azhdarchids, it
isn’t a good wader or swimmer due to it’s small and compact feet, though it will
do so occasionally. It’s rostrum is filled with sensitive tissue, allowing it to
detect borrowed prey and dig it out. It’s jaws are more robust than those of the
average azhdarchid, and it does have stronger jaw muscles, allowing it to break
smaller shells. Larger ones are delt with by opening them with the beak, the
lower jaw curved upwards for this function.

Once thought to be an hastazhdarchine, the Dupap’s true place within
Azhdarchidae is something of a mystery, though it does share with the Dudu the
atavistic first metacarpal. During the mating season, both sexes bear a small
red keratinous crest in the lower jaw. Females bury their eggs in sand,
particularly alongside riverbanks; both parents protect the nest, distracting or
harassing predators away. The young that bury their way out of the nests are
left to fend for themselves.

New insights on azhdarchid LK radiation

Pterosaur overlords of Transylvania: short-necked giant azhdarchids in Late
Cretaceous Romania

Mark Witton , Matyas Vremir , Gareth Dyke , Darren Naish , Stephen Brusatte &
Mark Norell

Azhdarchid pterosaurs are well known for their frequent attainment of gigantic
wingspans (sometimes over 10m), but are also characterised by a distinctive
anatomical bauplan which is thought to be fairly uniform across the group. This
comprises elongate jaws, long limbs and short wing fingers, as well as
hypertrophied cervical vertebrae, which are perhaps their most defining
features. We present evidence of unprecedented morphological diversity in giant
azhdarchids with EME 315, a large and robust seventh cervical vertebra from the
Maastrichtian Sebeş Formation of Transylvania. The specimen corresponds in
size, histology and proportions with the 10m wingspan Transylvanian azhdarchid,
Hatzegopteryx thambema, and likely represents a member of this genus or an
extremely close relative. Despite its size, EME 315 is proportionally short and
likely represents a cervical III-VII length of only 1.39m. This is comparable to
the neck lengths of much smaller azhdarchids and considerably shorter than our
estimated cervical III-VII length for Arambourgiania philadelphiae (2.3m),
another giant azhdarchid known from cervical remains. We therefore propose that
long necks are not common to all azhdarchids. The robust and short-necked
azhdarchid bauplan may reflect adaptation to predating relatively large animals,
assuming that, as suggested for other azhdarchids, these Transylvanian
pterosaurs foraged terrestrially. Because Transylvanian azhdarchids dwarf
contemporary terrestrial predators by some margin, it is possible that they were
apex predators in Maastrichtian Transylvania. This suggestion conflicts somewhat
with hypotheses that Late Cretaceous pterosaurs were ecologically constrained
and declining into extinction during the Maastrichtian.

Flying Pelecanimimus?

My distressingly poor attempt at illustrating my proposal.

With the discovery that ornithomimids had wings, a new possibility for Pelecanimimus has emerged:

Pelecanimimus does have large paired sterna with ossified ribs and possibly uncinates, so maybe basal ornithomimosaurs were more flight-y anyway.”

Mickey Mortimer.
So far, no other explanations were offered for these skeletal structures, and honestly, I don’t think there are any other possibilities other than flapping adaptations.

Since WAIR is extremely controversial, given the relatively low angle the arms could be raised at (and even then, this is not well established), flight is actually the more sensible explanation; an animal capable of powered flight needs robust bones and extensive musculature, but not as much as an animal that practises WAIR.

If Pelecanimimus was a flyer, this opens a wide range of implications. For starters, it shows that flight evolved independently in at least two lineages of dinosaurs (or more, given that microraptorines, Archaeopteryx and Rahonavis might had become volant independently from birds, after all; however, do note that, as Mortimer proposes, ornithomimosaurs as non-paravians isn’t well established, so they might be highly derived archaopterygids), that the size limit for flying non-ornithurine dinosaurs was considerably larger than previously thought (and that flight development might also not be reserved for small animals), that pterosaurs indeed co-existed with flying dinosaurs for most of their temporal range, et cetera. To say nothing about the fact that Ornithomimus and kin really were ratite mimics.

If Pelecanimimus was indeed a flyer, it was almost certainly a soarer, as even it’s unique anatomy would perhaps be insuficient for a Galliforme-like extreme flapper. Given what we know of other flying non-avian dinosaurs, hindwings would had been very likely present. Hindwings were indeed quite vital for non-avian dinosaur flyers, as the inferred gliding models for Microraptor show that these animals could gain some altitude simply by raising them at an angle, and this could explain why their anatomy is often underdeveloped when compared to modern birds.

Inferred gliding model for Microraptor. Note that, in mid-flight, the animal’s trajectory gains height, forming a U like curve, simply by raising it’s hindwings. If applied to long term flight, while the animal would gradually loose altitude, it would have remained airborne for an ostensibly immense period of time. Cobined with complimentary wing strokes, the end result would be a long, but relatively low energy demanding flight.

A terrestrial bustard/crane like lifestyle was likely, which would have been quite interesting as it lived in a time when chaoyangopterid and tapejarid pterosaurs were at their prime. This further indicates that niche partitioning between “birds” and pterosaurs ensured little direct competition, although the absence of chaoyangopterids in the area Pelecanimimus lived in and the low diversity of flying ornithomimosaurs seems extremely suspect.