sexta-feira, 10 de Abril de 2009

Pterosaur essay

Basically an essay for my personal project (as well as for JPL's "New Dinosaurs").
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Out of all flying vertebrates that ever lived, pterosaurs are probably the most impressive ones. Specialized winged sauropsids, these produced the largest fliers ever, and produced an unique set of adaptations for life in the air. Their wings are composed of a complex membrane composed of not only skin, but also muscle and collagen fibers (used to make it stronger and keep its shape while flying), and that is supported by the arm and a very long fourth finger, that is attached to the body and extended along it until the ankles. In addition they also have a smaller membrane that attaches to the shoulder and runs across the arm (propatagium), which ends on an elongated wrist bone known as pteroyd, used in the same way as birds use their allula; another membrane runs along the legs (uropatagium). Pterosaurs have an air sac pulmonary system, pretty much like dinosaurs, very efficient for the high oxygen demands of their warm blooded metabolism. The advanced pterodactyloid pterosaurs have also other adaptations for flight, such as a nasoanteorbital frenestra (a fusion of the nostril with the anteorbital frenestra, a "hole" in the skull of archosaurs between the nostril and the orbit), a notarium (a fusion of dorsal vertebrae, used to stabilize the body during flight), long metacarpals (so that the weight of the wing membrane doesn't fall all on the wing finger; it also aids on terrestrial locomotion) and short tail; more advanced species also lack teeth. Pterosaurs reproduce via egg laying, burrying their eggs on the ground. While some species might show parental care, the "flaplings" are nonetheless precocial, being able to fly since they are born, and because they already start looking for food they occupy several niches across their lifetime (which means a smaller species diversity compared to birds)



Pterosaurs first appeared in the Triassic, as long tailed primitive forms such as Eudimorphodon. They seem to have had evolved from basal ornithodirans like Lagosuchus, which also gave rise to dinosaurs. Soon they dominated the air, and these basal forms became very diverse until the end of the Jurassic, when the first pterodactyloids evolved; indeed, only anurognathids seemed to had survived. Pterodactyloids soon diversified, producing a larger amount of species taking over a lot more niches. Then, towards the middle Cretaceous, they seemed to that been declining, as only the larger genera appear in the fossil record; however, smaller ones did had survived, only that they were sheldomly preserved in the fossil record (at least until the Eocene, when they reappear in laggerstaten fossil sites like Messel, absent from the late Cretaceous). As the Cenezoic came, they preserved a middle diversity; the Paleocene/Eocene Thermal Maximum exterminated the pelagic pteranodonts, while the later Pliocene cooling caused extinctions in Europe and (to a lesser extent) in North America. Nonetheless, pterosaurs are still common and recolonised the regions they had disappeared from in the interglacial periods.

Anurognathoidea

The most basal living pterosaurs, and a somewhat poorly understood linage. Mainly nocturnal fliers, they avoid competion with pterodactyloids, and took a nightjar like lifestyle, feeding on moths and other night flying insects. Relying on vision to guide themselves, they share their environment with volaticothere mammals (bat analogues), which use sonar to find their way in the dark; anurognathids also have often bristles to sense the vibrations of flying insects, and down on their wing membranes in order to decrease the sound created by the wing flapping. Anurognathids are for all purposes Caprimulgiforme analogues, having a broad, short snout like insectivore birds have short and broad bills (making their heads somewhat frog like); they also have bigger uropatagia than pterodactyloids, supported by a very long first toe, acting like a the forked tail of insectivore birds. While there's not a lot of species diversity (35+) the ones present are quite common.


Anurognathidae


The typical anurognathoids, nocturnal animals with short and broad wings that live in forests. Barely changed since the Mesozoic, they are mostly aerial insectivores, but some became vertebrate predators like our world's frogmouths, and a particular species, the Cliff Ghast (Daemonognathus phillippullmani) became a large diurnal scavenger/predator from Eurasian mountain ranges, competing with predatory birds.

Ranorhynchidae

Although the earliest members of this clade seem to have first appeared in the Eocene, genetic data indicates a much older origin, probably dating from the Cretaceous or even earlier (though its unlikely modern looking species evolved prior to the Paleocene/Eocene periods. Unlike their more conservative relatives, they are diurnal, and so they lost adaptations like the down covered wing membranes and bristles, and have longer and thinner wings. As a whole, they resemble pterosaurian swallows (ence their english name, "swallow lizards"), and that even reflects itself where they lay their eggs; rather than burrying them, they actually build nests not too different from those of our world's swallows, keeping inaccessible to ground dweeling predators. There are more or less 13 species of these fliers divided in two genera, Hirundosaurus and Ranorhynchus, the first more common in Eurasia, Africa and the Americas while the other being restricted to Ocenia and Pacific islands (and yet with a larger species count).

Pterodactyloidea


The rest of the living pterosaurs belong to this clade, which has developed several adaptations absent in more basal pterosaurs as mentioned in the first paragraph of this essay.


Ctenochasmatoidea

A basal linage of pterodactyloids which included the famous Pterodactylus, they are notorious for their wading habits, having evolved large webbed feet for that purpose. Although they produced stork and heron like forms in the past, they all modern species (and most extinct ones) are filter feeders, using very thin and numerous teeth to trap small animals in their beaks. Smaller forms managed to survive in the Cretaceous, barely becoming preserved, and they only reappered significantly in the Eocene, when laggerstaten fossil sites also reappeared. Relatively more common in the northern hemisphere, they suffered a heavy blow when the ice ages came. Now days, a few species still exist, forming large flocks in wetland areas like flamingoes.

Ornithocheiroidea

Having declined since the Cretaceous, they are now reduced to a two cryptic species, the african Kongamato (Amphipterus africanus) and the Ropen (Lucipterosaurus aumalae). Both are aerial predators from rainforest and wetland areas, preying on small tetrapods and fish. They seem to be both solitary; the Kongamato is highly territorial and agressive, often attacking large animals that happen to be on their nesting sites. Little is known about the Ropen; it seems to be nocturnal, and its wing membranes glow due to a symbiotic relationship with a special specie of fungus.

Azhdarchoidea

Probably the most diverse linage of modern pterosaurs aside from anurognathids. Represented as the huge azhdarchids during the late Cretaceous, the globalization of rainforests drove the large species to polar areas or coastoal zones, since they couldn't live in the dense forests. The end result was that these pterosaurs diverged into three separate clades:

Neoazhdarchidae

Relatively conservative forms, they are hardly different from their Cretaceous relatives. They are divided into five species and their range pretty much covers all of the large landmasses.

Eunemicolopteridae

During the Eocene, a linage of azhdarchids decreased drastically in size via neoteny (since pterosaurs are highly precocial and occupy many niches across their lifetime, it would be fairly easy for them to start reproducing at an earlier stage of their lives and not needing to grow besides that phase anymore). Having specialized to a life in rainforests, these relatively small pterosaurs occupy niches occupied in our world by hornbills and toucans; this situation is rather the inverse than in our world's hornbills, as while grassland dweeling pterosaurs produced rainforest forms while rainforest dweeling hornbills produced savanna dweeling forms.

Apterocheiridae

Also in the Eocene, a linage of azhdarchids became isolated in Africa (then an island) and lost their ability to fly. Their wing membranes were lost (aside from a small membrane supported by a very reduced wing finger), and the usually plantigrade pterosaurian hind feet became digitigrade, just like the front ones (though not to that extreme). Their front feet (in a lateral position in most pterosaurs) also rotated forward, and their bodies became more robust. Being omnivores with carnivore tendencies, they took over the niches of oviraptors in Eurasia after the colision of Africa with that continent. In the americas, though, non-avimimid oviraptors (since avimimids took over small ornithopod niches) still remained somewhat dominant, specially after the interchange with South America that occured in the Pliocene. Apterocheirids are quite bizarre in the way how they reproduce; because pterosaurs lay eggs with very thin shells, ovivipary managed to evolve in these flightless forms, something that birds can't evolve due to their hard shelled eggs. Juveniles are protected by the parents, but more basal forms (most insular) don't display it; instead, the juveniles take an arboreal lifestyle, using wing membranes to glide (they later disappear aside from the vestigial structure, mentioned before)

[I'll give specie examples later]

sábado, 21 de Março de 2009

Cenozoic Pterosaurs

This topic is about speculative biology, so if you're a cryptozoologist, well, no cookies for ya. Okay, maybe, but not for creationists who uselessly attempt to use supposed living pterosaurs as evidence against evolution. JTFFDP (Já Te Fodi, Filho/a Da Puta [portuguese sentence, so usefull for insulting])
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As you can possibly imagine, speculating about a world were the K-T event didn't occured brings pterosaurs into the conversation.

The situation of these flying sauropsids in the Cretaceous is somewhat controversial; it is pretty obvious they achieved their golden age in the Early Cretaceous, when pterodactyloids produced a gigantic variety of forms, following the demise of basal pterosaurs, though anurognathids are present in laggerstaten fossil sites which only date in the Mesozoic from the Late Jurassic and Early Cretaceous (see below); interestingly, most ctenochasmatoid pterodactyloids also were found in laggerstaten fossil sites (again, see below). Pratically all pterodactyloid clades (aside from azhdarchids and pteranodontians) date from this era, and diversification within such clades is quite evident, specially in ctenochasmatoids, ranging from the very specialized filter feeder Pterodaustro to the equally specialized fisher Cearadactylus. Other clades show less extreme variations, but still notable (note the difference from the fishing ornithocheirids and the scavenging istiodactylids, both within Ornithocheiroidea).

Then, the fossil record seems to suggest a sudden disappearence of clades, and so only lonchodectids, ornithocheirids, pteranodontids and azhdarchids make it into the Late Cretaceous, and out of these only two clades survived beyond the Turonian (however, I pretty much assume the two last clades outcompeted the first two, since pteranodonts and azhdarchs only became notable in the late Cretaceous, following the dcline of the previous two clades). This, obviously, could be seen as that pterosaurs were suddenly declining and in the way of meeting a dire fate...

However, this might not be the case. As pointed out before, anurognathids are only known from laggerstaten fossil sites, and they appear in the Early Cretaceous, not just on the Late Jurassic. As a whole, these clade might actually have had a history as a Lazarus taxon, because all evidence points for a Triassic origin (they were the most basal known pterosaurs), and yet we lack Triassic fossils (and Triassic laggerstaten). Thus, its possible that they endured until the K-T event. Also, note that ctenochasmatoids were also mainly found in laggerstaten, thus probably also implying that they endured until the end.

Thus that leaves us with what? Four clades? Enough for me. Out of these clades, I'm assuming most would survive into the Cenozoic, had the asteroid not collided and ruined all the fun, except perhaps pteranodontians, because they were very specialized to a pelagic lifestyle, and the Paelocene/Eocene Thermal Maximum would probably exterminate them, as oceans are specially sensitive to climatic changes so extreme as those. Even if they survive they wouldn't pass the Eocene/Oligocene extinction event anyway. Of course, they could become smaller via neoteny, thus being reduced to small, adaptable forms. Whatever.

The other pterosaurs, well more adaptable, would obviously survive and diversify. In particular I can see a pterosaur diversity radiation lasting from the Eocene to the Miocene. Then, with the cooling of the climate, I'm assuming the flying reptiles would be hitten. Probably death to european and perhaps north american denizens, and the survivors could colonise those lands from the south, once the climate became warmer (such cycles, between retreat and return, would occur many times, since there were at least 32 ice ages in the last 2 million years).

Flightlessness in pterosaurs is likely, specially in azhdarchids and/or ctenochasmatoids, but I'd expect it to evolve only one or two times; bats never produced flightless forms after all, and while I hate the bat/pterosaur comparation I do have to agree that both were similar in one thing: the wing membrane, which extended unto the legs, would make it more difficult for them to produce fully flightless forms (birds, on the other hand, only need to loose the wing feathers to be flightless; they have their legs seperated from the wings after all). However, because pterodactyloids had reduced uropatagia, and an upright leg stance (like mammals and dinosaurs), it makes a flightless pterosaur more plausible than a flightless bat. For more info on wingless pterosaurs, see Darren Naish's post:

http://scienceblogs.com/tetrapodzoology/2008/09/come_back_lank.php

sábado, 7 de Março de 2009

Why pterosaurs weren't replaced by birds

Copyrighted from Richard Butler, Paul Barrett, Steven Nowbath & Paul Upchurch: "Estimating the effects of the rock record on pterosaur diversity patterns: implications forhypotheses of bird/pterosaur competitive replacement, SVP meeting abstracts2008, 59A":

"Pterosaurs formed an important component of terrestrial and marginal marine ecosystems during the Mesozoic, and were the first flying vertebrates. The fossil record appears to indicate a decline in pterosaur taxic diversity [ =species count] in the Late Cretaceous, followed by extinction at theCretaceous/Paleogene boundary. This reduction in species-richness has beenlinked to the ecological radiation of birds in the Early Cretaceous -- it has been proposed that early birds competitively excluded pterosaurs from many key niches. Hypotheses of competitive replacement are frequently posited based on the fossil record, but few have been tested in detail. Here we present a detailed examination of pterosaur diversity through time based upon a new comprehensive database of the spatial and temporal distribution of pterosaurs. We use this database to calculate taxic and phylogenetically corrected diversity estimates, and compare these estimates with a model describing temporal variation in rock availability. We use numbers of pterosaur-bearing formations (PBFs) as a proxy for rock availability;temporal variation in the number of PBFs is then used to generate a model in which rock availability is a perfect predictor of diversity. Both taxic and phylogenetic diversity curves are strongly correlated with numbers of PBFs, suggesting that a significant part of the signal contained within pterosaur diversity patterns may be controlled by geological and taphonomic megabiases rather than macroevolutionary processes. Moreover, significant differences between observed diversity and the diversity predicted by the rock availability model coincide with the occurrence of sites of exceptional preservation (Lagerstätten), again indicating major biases in the pterosaur fossil record. There is no evidence for a long-term decline in pterosaur diversity during the Cretaceous, although a reduction in species-richness might have occurred in the Late Cretaceous. Available data provide little support for the long-term competitive replacement of pterosaurs by birds."

domingo, 1 de Março de 2009

Niche map for WIW part 2

Note: I've replaced the "Filter Feeder" and "Diver" niches with "Waterbird" and "Fishing mammal", for accuracy reasons.

Asia

Tall Browser: Sauropod, Therizinosaur
Low Browser: Hadrosaur, Ceratopsid
Large Grazer: Sauropod/Ankylosaur, Hadrosaur
Medium Grazer: Hadrosaur, Therizinosaur, Pseudoungulate
Small Grazer: Bipedal Ornithopod, Pseudoungulate
Aquatic Herbivore: Ceratopsid, Afrothere, Multituberculate, Herbivorous Crocodillian*
Large Omnivore: Ornithomimid*/Troodontid, Oviraptor, Ceratopsid
Small Omnivore: Afrothere, Pseudoungulate, Glire, Galliforme/Paleognath/Oviraptor
Large Insectivore: Afrothere, Alvarezsaurid, Specialized Troodontid/Unenlagiine/Noasaur/Therizinosaur (see below)
Small Insectivore: Afrothere, Metatherian, Cimolestan
Top Predator: Abeliosaur/Noasaur, Tyrannosaur
Medium Predator: Tyrannosaur, Dromeosaur, Hyeanodont/Mesonychian/Metatherian, Crocodillian
Small Predator: Troodontid/Unenlagiine, Hyeanodont/Mesonychian, Crocodillian, Monitor, Metatherian
Aquatic Predator: Crocodillian, Mosasaur, Plesiosaur
Arboreal Herbivore: Specialized Primate, Gondwanaviforme, Multituberculate, Arboreal Ornithopod
Arboreal Omnivore/Frugivore: Primate, Cimolestan, Dromeosaur, Glire, Scadentian, Metatherian
Arboreal Predator: Hyeanodont/Mesonychian, Dromeosaur, Metatherian
Winged Frugivore/Nectar Feeder: Volaticothere, Flying Cimolestan/Primate, Galliforme, Apsaraviforme, Enantiornithe
Winged Insectivore: Enantiornithe/Neornithe*/Apsaraviforme, Anurognathid, Volaticothere
Winged Predator: Volaticothere, Enantiornithe, Anurognathid*
Winged Scavenger/Terrestrial Stalker: Pterosaur, Unenlagiine, Pseudodontorn, Paleognath
Waterbird: Anseriforme, Paleognath, Flamingo/Presbyornid, Grebe/Loon/Similar Bird, Hesperornithe, Pseudodontorn
Diving Mammal: Cimolestan, Afrothere, Metatherian
Random Oddity: Panda like Ceratopsid/Therizinosaur, Anteating Therizinosaur

*1.An idea I got just now. Probably it will replace the aquatic ceratopsids, or make them water buffalo analogues, while herbivore crocodillians would be hippo analogues
2.I think I'll replace them by either troodontids or flightless pterosaurs
3.I don't know if I should have insect/nectar eating neornithes; therefore, I'll only reffer insect/nectar eating birds as "birds"
4.Another idea I got just now

North America

Tall Browser: Therizinosaur, Hadrosaur/Sauropod
Low Browser: Hadrosaur, Ceratopsid, Meridiungulate
Large Grazer: Hadrosaur, Therizinosaur, Sauropod/Ankylosaur
Medium Grazer: Hadrosaur, Therizinosaur, Pseudoungulate
Small Grazer: Pseudoungulate, Bipedal Ornithopod, Xenarthran/Meridiungulate
Large Omnivore: Troodontid, Oviraptor, Ceratopsid
Small Omnivore: Metatherian, Glire, Xenarthran, Galliforme/Oviraptor/Screamer
Insectivore: Afrothere, Metatherian, Cimolestan, Xenarthran
Top Predator: Tyrannosaur
Medium Predator: Tyrannosaur, Dromeosaur, Hyeanodont/Mesonychian, Metatherian
Small Predator: Troodontid/Unenlagiine, Hyeanodont/Mesonychian, Metatherian
Aquatic Predator: Plesiosaur, Champsosaur, Crocodillian
Arboreal Omnivore: Cimolestan, Multituberculate, Glire, Dromeosaur, Metatherian
Arboreal Predator: Metatherian, Dromeosaur
Winged Omnivore: Volaticothere, Galliforme, Apsaraviforme, Enantiornithe
Winged Insectivore: Bird, Anurognathid, Volaticothere
Winged Predator: Volaticothere, Enantiornithe, Anurognathid
Winged Scavenger/Terrestrial Stalker: Pterosaur, Paleognath, Unelagiine, Ichthyorniforme
Waterbird: Anseriforme, Paleognath, Loon/Grebe/Similar bird, Hesperornithe
Diving Mammal: Cimolestan, Metatherian
Random Oddity: Can't think off

sábado, 28 de Fevereiro de 2009

Niche map for WIW part 1

Africa

Tall Browser: Sauropod (savanna), Hadrosaur (rainforest)
Low Browser: Ceratopsid, Hadrosaur
Large Grazer: Hadrosaur, Sauropod/Ankylosaur (ankylosaur like sauropods are welcome)
Medium Grazer: Hadrosaur
Small Grazer: Bipedal Ornithopod, Pseudoungulate*
Aquatic Herbivore: Afrothere, Multituberculate, Ceratopsid
Large Omnivore: Ornithomimid/Troodontid/Flightless Pterosaur, Oviraptor, Ceratopsid
Small Omnivore: Afrothere, Pseudoungulate, Glire*, Galliforme/Paleognath/Oviraptor*
Large Insectivore: Afrothere, Alvarezsaurid, Specialized Troodontid/Unenlagiine/Noasaur
Small Insectivore: Afrothere, Metatherian, Cimolestan
Top Predator: Abelisaur, Noasaur
Medium Predator: Tyrannosaur, Dromeosaur, Hyeanodont/Mesonychian*, Crocodillian
Small Predator: Troodontid/Unenlagiine, Hyeanodont/Mesonychian, Crocodillian, Monitor
Aquatic Predator: Crocodillian (obviously), Plesiosaur, Mosasaur
Arboreal Herbivore: Specialized Primate, Gondwanaviforme*, Multituiberculate
Arboreal Omnivore/Frugivore: Primate, Cimolestan, Dromeosaur*, Glire
Arboreal Predator: Hyeanodont/Mesonychian, Dromeosaur, Metatherian
Winged Frugivore/Nectar Feeder: Volaticothere, Flying Cimolestan/Primate, Galliforme*, Apsaraviforme, Enantiornithe
Winged Insectivore: Enantiornithe/Neornithe/Apsaraviforme, Anurognathid, Volaticothere
Winged Predator: Volaticothere, Enantiornithe
Winged Scavenger/Terrestrial Stalker: Pterosaur, Unenlagiine, Pseudodontorn, Paleognath
Filter Feeder: Anseriforme, Flamingo/Ornithomimid/Presbyornid
Diver: Hesperornithe, Loon/Grebe/Similar bird*, Pseudodontorn, Cimolestan, Afrothere, Metatherian
Random Oddity: Therizinosaur

*1.I don't know what Pseudoungulates should be, aside from the fact they are Placentals
2.There are glires, though neither rodents nor lagomorphs, just basal forms like Anagale
3.The competitors for the fowl niche
4.Not sure about which should be present
5.A linage of hoatzin like enantiornithes I once suggested
6.There are arboreal dromeosaurs, probably Kay's concepts
7.Like in Spec there are arboreal galliformes everywhere, being WIW's parrots
8.I haven't decided; loons are as old as penguins and petrels, but if flamingoes are present their closest relatives, grebes, should be present as well.

Europe

Tall Browser: Therizinosaur
Low Browser: Hadrosaur, Ceratopsid, Pseudoungulate
Large Grazer: Hadrosaur, Therizinosaur
Medium/Small Grazer: Hadrosaur, Therizinosaur, Pseudoungulate
Aquatic Herbivore: Ceratopsid, Multituberculate, Afrothere, Anseriforme
Large Omnivore: Ornithomimid/Troodontid, Oviraptor, Ceratopsid
Small Omnivore: Afrothere, Pseudoungulate, Glire, Galliforme/Paleognath/Oviraptor
Insectivore: Afrothere, Metatherian, Cimolestan
Top Predator: Tyrannosaur, Dromeosaur
Medium Predator: Tyrannosaur, Dromeosaur, Hyeanodont/Mesonychian/Metatherian
Small Predator: Troodontid/Unenlagiine, Hyeanodont/Mesonychian, Metatherian
Aquatic Predator: Plesiosaur
Arboreal Omnivore: Cimolestan, Multituberculate, Glire, Dromeosaur
Arboreal Predator: Dromeosaur, Metatherian
Winged Omnivore: Apsaraviforme, Galliforme, Enantiornithe
Winged Insectivore: Enantiornithe/Apsaraviforme/Neornithe, Anurognathid, Volaticothere
Winged Predator: Volaticothere, Enantiornithe
Winged Scavenger/Terrestrial Stalker: Pseudodontorn, Pterosaur, Unenlagiine, Paleognath
Filter Feeder: Anseriforme, Flamingo/Ornithomimid/Presbyornid
Diver: Hesperornithe, Loon/Grebe/Similar Bird, Pseudodontorn, Cimolestan, Metatherian, Afrothere.
Random Oddity: Arboreal Hyeanodont/Mesonychian, Flying Primate/Cimolestan in the Mediterranean, Sauropod in the same region

quinta-feira, 12 de Fevereiro de 2009

Bitchy Metazoica

It seems that fat whore that made Metazoica proves her arrognace and ignorance are equal to that of the most motherfucking creationist:

http://metazoica.blogspot.com/

Don't listen to what that fucking whore says; she clearly is ignorant

sábado, 7 de Fevereiro de 2009

Mark Witton vs John Conway

For those interested in pterosaurs, you might recognise these two artists, which seem to be on the leading positon on the pterosaur imagery/paleobiological speculation business (well, Mark is at least; John seems to have turned off, although he still seems to be alive). The whole purpose of this waste of time its too see which of these wonderfull artists depicts pterosaurs better and thus to see which one is decent/mentally sane/whatever.

Anyway, since I haven't asked for the permission of using their pictures, use the following links:

http://www.flickr.com/photos/markwitton/
http://jconway.co.uk/

And now we shall begin.

Favoured species

Mark Witton depicts many different pterosaur species; in fact, there not a single pterosaur group he missed. I still pity the fact that he largely ignored ctenochasmatoids (aside from Pterodactylus & Pterodaustro, he didn't portrayed any other specie, which is a shame, because I really want to know his opinion on Cycnorhamphus and Cearadactylus), and he still rarely does non-pterodactyloid pterosaurs (aside from Dimorphodon). From the number of pictures he did, the pterosaur family he focused the most on was Azhdarchidae, and, truth to be told, it was quite predictable; after all, he was one of the two people responsible for showing the world they weren't skimmers but stork-like generalists, right? His first pictures of such animals were somewhat inaccurate (the first depicted them with a neck too thin and hunting in shallow water, the second showed a horrendous skinny thing, with thin wings in addition to the thin neck, and the third shows something akin to his first image but with a neck still too thin and taking off on a bird like fashion), but afterwards his were considered the best depictions of these pterosaurs on the net.

John Conway, on the other hand, seems to have a liking on a rival linage of flying reptiles, the Ornitocheiroids. His favourite species seem to be Anhanguera, Pteranodon and Nyctosaurus, which represent clades Ornitocheridae, Pteranodontidae and Nyctosauridae (if the later is distinct of the second, obviously). Other pterosaurs, however, received some attention from him; the ctenochasmatoid Pterodactylus, and the tapejarid Sinopterus (although he seems to regard Sinopterus and Nemicolopterus as distinct, the fact is that the later is a juvenile of the first, so...), however, still received some attention from him.

Pterosaur wing designs

Mark depicts pterosaurs with their patagium connecting to their legs/feet. This view, often considered quite old and unoriginal (after all, bats too have their wing membranes like that), might actually be very accurate, because evidence shows that many pterosaurs had their wing membranes connecting to their legs/feet, and quite possibly all pterosaurs were like this. The propatagium is well shown in his earlier pictures, with the pteroid rised and shown to be supporting two membranes: one between it and the shoulder and the other between it and the hand. Nowdays, though, his flying reptiles seem to have a smaller and more typical pteroid, with no membrane connecting it to the hand, thus having a single, more "traditional" propatagium. The uropatagium in his pterosaurs is quite big in basal species, to the point that it even connects the two legs, but that excludes the tail. In pterodactyloids, it is reduced to two small membranes running along both legs, which, according to him, is one of the reasons advanced pterosaurs had a better ground locomotion than their ancestors.

In John's pterosaurs, the wing structure is quite different. He depicts his pterosaurs with the wing membranes connecting to the hips, giving their wings a more avian shape. At the most they connect to the knees, but no further. The propatagium is pretty much as in birds; the pteroid is hardly visible, and he seems to think it might be able to inflate, like the ones of pelicans and some other birds. His uropatagium is composed of two distinct membranes running along the legs as in Mark's, but they are much more developed and almost make the back limbs resemble the tail feathers of birds like kites and frigate birds, and they could have had the same function. The feet are also webbed, further stressing the role of the feet in steering. The actinofibrils seem also to be more visble in his pterosaurs, making their wings more similar to those of birds.

Lifestyle depictions/implications

Mark presents a vivid alternative to the steryotypical view that pterosaurs are sea bird analogues. Based on actual evidence overlooked by nearly everyone else, he managed to show the possible real lifestyles of many pterosaur species. For instance, rather than fish eaters, his tapejarids are galliforme analogues, running or climbing in search of animal and plant matter (though his first picture of this group depicts a sea bird like animal, and the second a falcon like predator; however, at the time he wasn't as wise as he is now). Dimorphodon passed from a puffin like fish eater to a tree climbing predator, and, as we all know, azhdarchids are now seen as terrestrial thanks to him. The wings of his pterosaurs also reflect their lifestyles; terrestrial forms have shorter, broader wings, while his ornitocheiroids, while still having their membranes attaching to the legs, have much longer wings, thus resulting on a thinner wing shape. Overall, his pterosaurs are as diverse as our birds.

John Conway, on the other hand, offers a more limitated view on pterosaur ecology. Aside from Germanodactylus (portrayed as a small opurtonist), Pterodactylus (portrayed as a shore bird like prober) and Nemicolopterus (depicted as a robin like omnivore), and possibly Zhejiangopterus (seen on the ground, though no particular lifestyle is atributed to it), all of his pterosaurs seem to be sea bird analogues, using their thin wings to soar over coasts or seascapes. His Quetzalcoatlus, seen flying over a lake and with a neck quite shorter than Mark's, seems to be a skimmer (though its size seems to suggest that its a baby, not a full grown pterosaur), and his Sinopterus is implied to be a seagull or skimmer like form.

Conclusion

As a whole, I prefer Mark Witton. While John Conway has beutifull pictures, they are overall wrong in the anatomy and lifestyle of pterosaurs. Though they are too beutifull to go to waste, and certainly original, depicting pterosaurs as more bird like than bat like, they sadly lack the accuracy of Mark's works. I wish he uploads something new soon though; I'll ignore the wing membranes (as I always do; they look better in the way he depicts them anyway) as long as he shows pterosaurs that aren't sea bird like.