How Did Pteranodon Walk?

Earlier we looked at terrestrial locomotion in pterosaurs, discriminating a basal bipedal taxon from the quadrupedal track makers that can be matched to tracks attributed to ctenochasmatid, pterodactyloid (check out the animation!) and maybe even ornithocheirid pterosaurs (Peters 2000, 2010, 2011). We also looked at the many potential problems that surround the wing launch hypothesis and presented an alternative or two.

Pteranodon and especially Nyctosaurus (Fig. 1) were two special cases united by extremely long metacarpals coupled with relatively short hind limbs that prevented them from walking in the same manner as pterosaurs having shorter metacarpals.

 

Nyctosaurus reconstruction

Figure 1. Nyctosaurus reconstruction according to Bennett (1997) and Peters, both based on UNSM 93000. Click to enlarge.

Bennett’s Take on Nyctosaurus
Bennett (1997) provided a great illustration of Nyctosaurus “essentially bipedal” (Fig. 1) because the forelimbs could only touch the substrate on the “back” of the folded wing finger, so far in front of the jaw tips that they were unable to provide a thrust vector to the elbow and shoulder. The fingers were greatly reduced, perhaps because they were no longer in use. See Muzquizopteryx and  Nyctosaurus bonneri for extreme proportions within this clade. Even shorter metacarpals on pterosaurs don’t appear to contribute thrust, only support, especially when nosing around for food items buried in the substrate or swimming around their submerged ankles in the shallows.

Pteranodon
The Triebold specimen of Pteranodon NMC41-358 is the most complete one known (Fig. 2). Others had larger wings and shorter legs. In the Triebold specimen it appears difficult for the free fingers (especially fingers 1 and 2) to contact the substrate as in other pterosaurs due to the great length of the metacarpus relative to the hind legs.

Pteranodon walking animated

Figure 2. Pteranodon walking. Click to animate. Note the femur is drawn and moves in the parasagittal plane for ease of animation. When properly sprawled the butt would drop a wee bit. The feet may have been plantigrade. They are not well preserved in this specimen. Other Pteranodon have digitigrade pedes. Those closer to UALVP 24238 had plantigrade pedes.

Too Erect?
If the above animation was configured too erect, then imagine it with lower shoulders (Fig. 3). That moves the free fingers even further forward, further unable to contact the substrate (despite the cheating on finger placement here by ignoring the configuration of the metacarpals). In any configuration the forelimbs were more like adult crutches on a little kid, my friends: very awkward on land. And, obviously, secondarily evolved, interrupted by a bipedal phase in pre-pterosaurs and basal pterosaurs. 

Walking pterosaur according to Bennett

Figure 3. Click to animate. Walking pterosaur according to Bennett (1997). Note the forelimbs provide no forward thrust, but merely act as props. They probably provided braking in this configuration and would have compressed (flexed) on contact with the substrate, rather than extending to provide thrust as in all other tetrapods. Compare this reconstruction to the Bennett reconstruction of Nyctosaurus.

Send alternatives if you have them!

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bennett SC 1997. Terrestrial locomotion of pterosaurs: a reconstruction based on Pteraichnus trackways. Journal of Vertebrate Paleontology, 17: 104–113. online pdf
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D. 2010. In defence of parallel interphalangeal lines. Historical Biology 22:437-442.
Peters David 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos, 18: 2, 114 —141

The Pterosaurs of Fantasia (1940)

In 1940 Walt Disney stunned the world with his tribute to classic music, an animated movie called Fantasia. In his tribute to Stravinsky’s Rite of Spring (Le sacre du printemps), Disney featured versions of Dimorphodon and Pteranodon, two of the several dozen pterosaurs known at that time.

Disney’s Dimorphodon
Disney’s prescient depiction of Dimorphodon (Fig. 1) correctly provides this pterosaur with the Zittel wing, stretched between the elbow and wingtip without contacting the hind limbs, which are incorrectly splayed.

Disney Dimorphodon

Figure 1. Disney's prescient depiction of Dimorphodon awakened by a theropod and flapping over a pelycosaur from Fantasia (1940), recovered from YouTube.com.

Disney’s Pteranodon
Following the famous Smithsonian mount, the paradigm at the time, Disney incorrectly depicted Pteranodon with wings stretched to the ankles. Not much muscle on those arms, another tradition that is disappearing today. The free fingers correctly point ventrally. Looks like the left foot has toes flexing laterally, just the opposite of the knees, which are correctly splayed and followed by another prescient set of uropatagia! Here again the limb musculature in the thigh is sorely lacking.

Disney's Pteranodon

Figure 2. Disney's Pteranodon from Fantasia (1940) recovered from YouTube.com.

Despite These Problems
No doubt, Disney’s images in Fantasia inspired more living paleontologists than anyone realizes despite the various problems we recognize today (like the overweight, tail-dragging, swamp-dwelling sauropods). The spirit Disney gave his dinosaurs and pterosaurs trumps any shortcomings in the images themselves.

Paradigms of Their Time
Disney’s images were all considered paradigms of paleo traditions in the 1930s and 1940s, but many of those paradigms have changed since then. This gives me hope that someday a pterosaur renaissance will follow in the footsteps of the recent dinosaur renaissance and soon pterosaurs will also be commonly depicted with strict adherence to the fossil record.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
wiki/Fantasia
YouTube/Rite of Spring from Disney’s Fantasia

A Closer Look at the “Catapult Mechanism” in Pterosaurs

There seems to be a continuing interest in the pterosaur wing launch hypothesis championed by Mike Habib. It’s a weekly favorite. Here’s another illustration (Fig. 1) that should clarify certain problems found in the Habib/Molnar concept. Mike and I have talked about this at length with no movement on either side.

The so-called catapult mechanism in pterosaurs

Figure 1. Left: The so-called catapult mechanism in pterosaurs. Right. The actual design of pterosaur hand (in this case Anhanguera/Santandactylus). Click to enlarge. Note there can be no pinching of the extensor tendon beneath the weight of the pterosaur for the reasons illustrated here and explained in the text. The metacarpals were not configured on the dorsal (in flight) or lateral (on the ground) side of metacarpal 4 in ANY pterosaur specimen. They were anterior whether your follow Bennett's (2008) stacked metatarsal interpretation or mine (links in text).

In Science it is Important to Expose Errors 
And that’s why in every blog I encourage those who have updated data to alert me to errors that I produce. In this case a reconstruction and a hypothesis promoted on pterosaur.net are reexamined and challenged.

Forewing Launch and the Catapult Mechanism
Dr. Mike Habib (2008) proposed a fore wing launch method for pterosaur take-off which was illustrated by artist Julia Molnar online (and see above, left). A catapult mechanism (as in grasshopper hind legs) was specified to increase the power of the launch. Unfortunately the illustration by Molnar (Fig. 1) includes several errors which preclude the possibility of a catapult mechanism in pterosaurs.

Molnar illustrated metacarpals 1-3 way too short. On the right the correct length is indicated. All four metacarpals were actually the same length. That means fingers 1-3 extended beyond the metacarpus. Pterosaur manus ichnites only impress digits 1-3. No trace of digit 4 ever impressed. Thus there was no pinching of the extensor tendon beneath the weight of the pterosaur to load the catapult prior to launching.

Furthermore, as in lizards, the long metacarpal extensor actually split prior to the knuckles to insert on the medial and lateral sides of the proximal phalanges. They did not extend over the knuckle. Much smaller muscles and tendons, the digit extensors (see above and here) extended over the knuckles.

Finally the flexors had to insert further distally than Molnar illustrates. In the Molnar illustration the flexors reach the limit of their ability to flex at 90 degrees. By inserting the tendon further distally flexion can continue until the wing finger is completely folded (see sequence here). More on pterosaur wing evolution here. More on the placement of pterosaur metacarpals here.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E Buffetaut and DWE Hone eds., Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Habib M 2008. Comparative evidence for quadrupedal launch in pterosaurs. Pp. 161-168 in Buffetaut E, and DWE Hone, eds. Wellnhofer Pterosaur Meeting: Zitteliana B28

Pterosaur.net/anatomy

An Obligate Bipedal Basal Pterosaur

The Traditional View
All pterosaurs were quadrupedal, based on trackway evidence.

MPUM 6009, the Milan specimen, the most primitive known pterosaur

Figure 1. The most primitive known pterosaur, the Milan specimen, MPUM 6009. The long hind limbs and relatively short fore limbs were homologous with those in Sharovipteryx and Longisquama. The extremely slender tail is most like that of Sharovipteryx, not later pterosaurs which thickened the tail with elongated chevrons and zygapophyses. Gray tones represent possible soft tissues, homologous with those in Cosesaurus and Longisquama.

The Heretical View
One basal pterosaur, MPUM 6009 (Wild 1978), was an obligate biped, retaining the long-legged morphology of its ancestral sisters, Sharovipteryx and Longisquama. All pterosaurs following MPUM 6009 (such as Raeticodactylus and Eudimorphodon) had shorter hind limbs and longer forelimbs, a combination that enabled quadrupedal locomotion.

MPUM 6009 was considered a small Carniadactylus by Dalla Vecchia (2009), but the differences are many.

MPUM 6009 in situ.

Figure 2. MPUM 6009 in situ. Click to enlarge and portray the Wild (1978) interpretation. Bones, impressions of bones and some soft tissue complete this articulated skeleton at the very base of the Pterosauria. The crushed skull required reconstruction. Here, using the DGS method, the bones have been colorized. This permits subtle impressions to be identified. Sister taxa share many of these traits, confirming their identity.

Longer Legs, Shorter Forelimbs
Here the reconstruction tells the tale. Question is, is the reconstruction accurate? The clues are, admittedly ephemeral, yet even without such long legs, MPUM 6009 nests at the base of the Pterosauria. So long legs are not beyond the realm of possibility. The relatively short neck allies this basal pterosaur with Longisquama, the outgroup sister taxon. The laterally increasing toe length and deep pelvis also ally this taxon with Longisquama. The sternal complex is also essentially identical.

Ironically…
Such long legs and short forelimbs “ally” this pterosaur with Scleromochlus, and basal dinosaurs, but — really, seriously — hardly at all. It’s convergence!! So if anyone from the traditional camp wants to bitch about this reconstruction, think twice. You’ll only be shooting yourself in the foot. Things happen when the forelimbs are elevated off the substrate, as we humans all can attest.

Bipedal lizard video marker

Figure 3. Click to play video. Just how fast can quadrupedal/bipedal lizards run? This video documents 11 meters/second in a Callisaurus at the Bruce Jayne lab.

How Living Lizards Run Bipedally
The Bruce Jayne Lab in Cincinnati, Ohio, has produced a video of a zebra-tailed lizard (Callisaurus) in fast quadrupedal and bipedal locomotion filmed on a treadmill. When the fore limbs are elevated the hind limbs go digitigrade. The speed is an incredible 11 meters per second.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.)rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Eudimorphodon

Anurognathids as Apodiform Analogs


Batrachognathus

Figure 1. Batrachognathus volans. Note the binocular fields of vision enabled by the narrow nasals not found in basal anurognathids. Also note the tiny rod-like palatal processes of the maxilla ventral to the ectopalatine (ectopterygoid + palatine) and pterygoid. These are likely touch sensors when the mouth is open during feeding. Click to learn more.

Anurognathids are different from the other pterosaurs. Forsaking the long pointed rostrum, anurognathids evolved a short wide gape that ultimately produced binocular vision with the narrowing of the nasals in derived taxa, such as Batrachognathus (Fig. 1). The wide gape has long been recognized as an excellent flying insect trap. This gape was taken to its largest arc in the vampire anurognathid pterosaur, Jeholopterus and its widest gape in the “flathead” anurognathid, mistakenly attributed to Anurognathus.

Here we’ll compare Batrachognathus with its modern analogs among birds, the swift (Apus apus, Figs. 2) and the nightjar (Caprimulgus), both members of the Apodiformes.

The skull and skeleton of Apus apus,

Figure 2. The skull and skeleton of Apus apus, the Common Swift.

Swifts and Nightjars (Nighthawks in the Western Hemisphere)
Spending most of their lives in the air, swifts feed on insects caught on the wing during daylight hours. They cling to vertical surfaces when they stop flying, never settling on the ground due to the small size of their hind limbs. By contrast, nightjars (Fig. 3) usually nest on the ground, despite their small feet, which are also of little use in walking. Nightjars feed on moths and other large flying insects and are most active nocturnally.

A nightjar with mouth wide open.

Figure 3. A nightjar with mouth wide open. Photo courtesy of Peter Sjolte Ranke.

Anurognathids
The large eyes of Batrachognathus indicate a possible nocturnal lifestyle.  Bristles surrounding the jaws were reported in Batrachognathus (Rjabinin 1948). These were compared to the rictal bristles surrounding the jaws of many birds, but are more prominent in nightjars. In Batrachognathus the tip of the short tail is nearby and thus could represent tail tip bristles. Rictal bristles are not found in sister pterosaurs, but tail tip bristles are.

In contrast to apodiforms, anurognathids retained relatively large hind limbs, so Batrachognathus would have retained excellent walking and running abilities. (Note the right angle femoral head in Batrachognathus, giving it a parasagittal stride.)

Nighthawk Wings
Flying over the crowds at Friday night football games, nighthawks (Apodiformes) find and devour moths that are attracted to the stadium lights. With their stiff, elliptical-tipped, narrow-chord wings, nighthawks remind me of anurognathids.

Your thoughts?

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bakhurina NN 1988. [On the first rhamphorhynchoid from Asia: Batrachognathus volans Riabinin 1948, from Tatal, western Mongolia]. Abstract of paper in Bulletin of the Moscow Society for the Study of Natural History, Geological Section 59(3): 130 [In Russian].
Rjabinin AN 1948. Remarks on a Flying Reptile from the Jurassic of Kara-Tau. Akademia Nauk, Paleontological Institute, Trudy 15(1): 86-93.

wiki/Batrachognathus
wiki/Common_Swift
wiki/Nightjar

Swift skeleton based on data from skullsite.com

The Pterosaurs From Deep Time: Nits and Picks #2

The Pterosaurs From Deep Time by Dr. David Unwin

Figure 1. The Pterosaurs From Deep Time by Dr. David Unwin

In 2005, Dr. David Unwin, one of the top experts on pterosaurs, authored a popular book on pterosaurs, The Pterosaurs from Deep Time. This is part 2 of the Nits and Picks. Here is part 1.

Unwin p. 230
“The exact point at which the pterosaurs branched off from other diapsid reptiles is not at all clear, and intermediate forms between pterosaurs and other reptiles have yet to poke their heads out from the fossil record (or if they have done so, they are keeping their identity well-hidden).”

This is Dr. Unwin creatively ignoring Peters (2000a, b, 2002) which introduced the fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama, plus the non-fenestrasaur Langobardisaurus, as pterosaur precursors/sisters. Why would he do this? Instead Unwin (2005, p. 231) promoted an imaginary creature, a lizard-like, tree-climbing sprawler without manual digit 5, with a hyperelongated manual digit 4, a large muscular tail and extradermal membranes between the extremities. Bizarre. Why was it lizard-like with sprawling hind limbs when Bennett (1996), Benton (1999) and Senter (2003) reported that upright, bipedal and digitigrade Scleromochlus was a pterosaur sister? Even highly criticized Cosesaurus was upright, bipedal and digitigrade. This imaginary creature seems to have been chosen only to provide a platform on which to add extensive dermal membranes (but then flying squirrels also have upright limbs!).

Unwin, p. 232
“It seems possible, then, that insects powered pterosaurs to a true flapping flight ability.” Then slightly later, “really big insects are quite common in the Carboniferous and Permian, but disappear in the Late Triassic, at just the time that pterosaurs are thought to have taken to the air. Coincidence? Perhapss, but at the moment, an insect-powered origin of flight for pterosaurs is the only reasonable theory on the table.”

Incredible! By eating giant flying insects to extinction Unwin (2005) thinks pterosaurs were “powered” to flapping flight. Gaaakk!! This doesn’t even attempt to address morphology but hangs the “important” question on diet. Unwin (2005) doesn’t mention that pre-flapping pterosaur precursors were also insect-eaters, or that the giant insects would have been larger and more agile in the air than basal pterosaurs. He also ignores the explanation for wing evolution provided by Peters (2002) based on fenestrasaur morphology and the gradual acquisition of pterosaurian traits.

Unwin p. 241
In trying to explain the extinction of long-tailed “rhamphorhynchoid” pterosaurs (after 75 million years of success), Unwin reported, “the problem lay…when rhamphorhynchoids were on the ground…with their arms and legs shackled together by the cheiropatagium and a large cruropatagium draped between the legs.”

Of course this ignores the fact that all Triassic and Early Jurassic “rhamphorhynchoids” were extinct by the Late Jurassic, so extinction was happening continually and proceeded to continue in “pterodactyloids” throughout the Cretaceous. This also hangs all the “rhamphorhynchoid” problems on the false interpretation of the Sordes uropatagium (aka cruropatagium) discussed earlier.

Unwin, p. 244
“Pterodactyloids’ appearance in the Late Jurassic is almost as dramatic as the debut of pterosaurs in the Triassic. Frustratingly, we still have no evidence for their ancestors…”

So imagine Unwin’s excitement when he was presented Darwinopterus! Lü, Unwin, Jin, Liu and Ji (2009) considered it the long-sought link. No wonder they invented “modular evolution” to explain away the “pterdactyloid” skull and neck attached to a “rhamphorhynchoid” post-cervical region. Unfortunately his cladogram recovered 500,000+ trees with no resolution surrounding Darwinopterus. That should have been a red flag.

No, “pterodactyloids” had four origins and darwinopterids represent a fifth departure from basal pterosaur patterns as demonstrated by the large study. Furthermore Unwin’s cladogram ignored the tiny pterosaurs, which are key to understanding the four origins of the “pterodactyloid”-grade pterosaurs.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Peters D 2000a.
 
Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7(1): 11-41.
Peters D 2000b.
 A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, DeKalb, IL, 1-279.
Unwin DM 2005.
The Pterosaurs: From Deep Time. Pi Press, New York.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

The Pterosaurs From Deep Time: Nits and Picks #1

The Pterosaurs From Deep Time by Dr. David Unwin

Figure 1. The Pterosaurs From Deep Time by Dr. David Unwin

In 2005, Dr. David Unwin, one of the top experts on pterosaurs, authored a popular book on pterosaurs, The Pterosaurs from Deep Time. Essentially it updated the pterosaur facts and hypotheses of its predecessor, The Encyclopedia of Pterosaurs (Wellnhofer 1991). Unwin wrote: “Much has changed since the Encyclopedia first appeared. The many critical ideas about pterosaur biology that were fought over in the 1990s… have been resolved into a convincing and (among pterosaurologists) widely agreed-upon picture.”

That is true. Most pterosaurologists do agree with the concepts, observations and hypotheses contained in Deep Time. However one pterosaurologist, the heretic among us, tends to disagree … often. That goes both ways, of course. Dr. Unwin completely ignored the pterosaur foot, origin and flight membrane hypotheses published by Peters (2000a, b, 2002) and they were not included in his otherwise complete and extensive bibliography. Rather than exploring opposing topics and throwing arguments against them, Dr. Unwin pretended that they never existed. That’s a shame, because that was a great opportunity for Dr. Unwin to really let me have it.

Today’s topic of juvenile and tiny pterosaurs will highlight several topics and ideas from Deep Time that do not agree with the evidence.

Unwin, p 142
“As a rule, this means that juveniles tend to be uncommon in the vertebrate fossil record, and individuals at very early stages of growth (newborn or even prenatal), are rare or unknown — except, oddly enough, in pterosaurs.”

Unfortunately Dr. Unwin considered all tiny pterosaurs to be newborns and juveniles when phylogenetic analysis (and other evidence, see below) indicates that they, too, are adults. In pterosaurs size reduction was a trait of transitional taxa in most clades. Most pterosaurologists do indeed consider a short snout and large orbit to be a juvenile character, but actually it is just a scaphognathine trait. As lizards, pterosaurs did not follow archosaur growth patterns but developed isometrically (embryos looked just like parents). The JZMP and Pterodaustro embryos falsify the traditional short-snout, large-orbit hypothesis. Many other tiny pterosaurs also had a long snout (see below). The third embryo, the IVPP specimen, came from parents with a short snout, but the eyes were still smaller than originally published.

Pterodaustro embryo

Figure 2. Pterodaustro embryo. There certainly is no short snout/large eye here!

Dr. Unwin, p. 151
“The snout often grew faster than neighboring regions, so that large-eyed short-face flaplings finished up with long, low skulls and relatively small eyes.”

Some tiny pterosaurs, like B St 1936 I 50 (no. 30 in the Wellnhofer 1970 catalog) and Senckenberg-Museum Frankfurt a. M. No. 4072, (no. 12 of Wellnhofer 1970), do not have a short snout and large orbit. (Click the blue links to see them).

Dr. Unwin, p. 156
“…there doesn’t seem to have been any “small” species, which is even stranger than you may think. Consider that the vast majority of birds and bats are less than one-third of a meter in wingspan. By contrast, adutls of the smallest pterosaur species known at present, such as Anurognathus ammoni, are at least 40 cm in wingspan, and most of them are bigger. A biased fossil record? Hardly. Otherwise, we wouldn’t have found all those flaplings and juvenile…”

Once again, if something is apparently missing, but replaced by something identical to it, it’s not wise to prejudicially ignore what is present. Test the oddities and autapomorphies with a phylogenetic analysis and you too will discover that those “flaplings” were adults of several “small” species.

Dr. Unwin p. 156
“This suggests a rather surprising conclusion: Young pterosaurs were the small species, or at least occupied some of the living spaces (niches) in which one might have expected to encounter small adults.”

So close, yet so far… mmmm. If only Dr. Unwin had performed a phylogenetic analysis instead of taking a falsified tradition at face value. Phylogenetic analysis is key to understanding the pterosaurs. But it only works when they are all included, as demonstrated here.

More on Deep Time later.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London: Salamander. 192 pp.

Quetzalcoatlus, in Flight

A note added November 12, 2020
Quetzalcoatlus was flightless due to clipped wings (vestigial distal wing phalanges). Here is the link on that data.

As a Guide to Artists and Modelmakers
Many artists add pterosaurs to their illustrations and many model makers have been assigned the task of reconstructing flying pterosaur skeletons for museums. This blog is here to provide some heretical suggestions that, doggone it, make more sense all the way around!

Quetzalcoatlus in dorsal view, flight configuration.

Figure 1. Quetzalcoatlus in dorsal view, flight configuration. Inset: a full-scale model at the Texas Memorial Museum.

Properly Configuring Quetzalcoatlus in Flight – The Knees
It is a common tradition to extend the hind limbs behind flying pterosaurs and, judging by the full-scale model at the Texas Memorial Museum (TMM, Fig. 1), this practice also extends to the largest of them all, Quetzalcoatlus. Imagine the mechanical strain at the ball joint of that extended femur!  Unfortunately that configuration also assumes a dinosaur-like right angle femur for Quetzalcoatlus, something only basal pterosaurs had. Q and its sisters had sprawling, lizard-like hind limbs, yet still able to place the feet beneath the torso as blogged earlier, and as shown here. Plus, extending the legs posteriorly gives the uropatagia (preserved not on Q but on other pterosaurs) nothing to do. Finally, the large thigh muscles originating from the anterior ilium would have been overextended if the leg was posteriorly oriented.

Much better to extend the sprawling femur in a sprawl: laterally with the knees not drooping too much. Then extend the tibia in the same plane. This gives Q a horizontal stabilizer (Fig. 1), like an airplane and echoes the hind limbs of Sharovipteryx, a pterosaur forebearer. In flight, the legs would have provided their own lift in this configuration, without additional strain on the hips to hold them up in the airstream.

Properly Configuring Quetzalcoatlus in Flight – The Feet
In the TMM model the soles of the feet are pointing to the sky. This give the feet nothing to do but dangle. However, with the knees and shins out, the soles point medially, back to the tail root between them. Spreading the toes allows the skin between them (preserved on other pterosaur specimens) to form aerodynamic surfaces to create lift. In this case the lift would be lateral, which pulls the feet out laterally, which helps the knees to stay extended with less effort, again, as in Sharovipteryx.

Properly Configuring Quetzalcoatlus in Flight – The Elbows
It’s traditional to extend the elbows straight out from the chest laterally, then extend the wrist straight out from the elbow. In birds and bats this would be considered over-extension. In Q let’s move the elbows back to where birds and bats put them and let’s raise the elbows slightly to provide the wing some curvature. Everyone knows a wing should be curved. Funny how few pterosaur artists add this subtle but vital element.

Properly Configuring Quetzalcoatlus in Flight – The Wing Finger
The model makers of Q. correctly included a substantial angle between metacarpal 4 and digit 4, following a natural stop in the specimen. This is different than in other pterosaurs, like Anurognathus and Nyctosaurus, in which the fully extended wing finger virtually lines up with the fourth metacarpal. This gives the Q wing a deeper chord at the base of the flight finger. This depth may be related to the brevity of phalanx 4 giving Q more of a duck wing, than an albatross wing.

Properly Configuring Quetzalcoatlus in Flight – The Neck
The TMM model makers extended the neck in their full-scale Q about as far as it could go. However, soft-tissue fossil evidence (Frey and Martill 1998) in Pterodactylus indicates that the longer necks were supported by a tall, narrow, muscle and tendon complex that spanned across the arc of a ventrally convex cervical series. So such a neck curve is integral.

Properly Configuring Quetzalcoatlus in Flight – The Head
No doubt Q could have moved its head anywhere it wanted to, but the standard flight position would have been “nose down” as reported (Witmer et al. 2003) in other long rostrum pterosaurs, like Anhanguera. It’s not that the back of the head drooped down. It was the front that did.

I Haven’t Yet Mentioned the Wing Membranes
But notice how nicely this configuration works with an independent hind limb not encumbered by the deep-chord wing membrane that is the modern paradigm. Read more about wing membranes here.

Footnote
The flying Q. model of Paul MacCready had the hind limbs tucked in, like a bird, following Kevin Padian’s reconstruction of the early ’80s. The model flew just fine. However with a sprawling femoral head, such a configuration would have been a strain on the animal and therefore highly unlikely. No one illustrates that configuration today.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Frey E and Martill DM 1998. Stissue preservation in a specimen of Pterodactylus kochi (Wagner) from the Upper Jurassic of Germany. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210: 421–441.
Witmer LM, Chatterjee S, Fransoza J and Rowe T 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behaviour. Nature 425:950-953. online pdf
Flying Pterosaur Model of Paul MacCready online pdf

Build Your Own Paper Pteranodon!

 Build Your Own Pteranodon Paper Model

Click to download pdf. Build Your Own Pteranodon Paper Model

Happy Thanksgiving (here in the USA)!

Download the pdf. Print out on 8.5×11″ “cover stock” paper.
Cut out the pieces. Fold them as instructed. Glue them together.
Run piano wire under the wings if you don’t want them to droop.
Hang on thread.

This model might fly, but the landing will bend the rostrum!

Enjoy!

From your friend at The Pterosaur Heresies.

Thanks for coming back.

Microtuban, a New Basal Azhdarchid

Microtuban altivolans (Elgin and Frey 2011) is a new basal azhdarchid pterosaur with the characteristic tiny fourth phalanx. Only the mid-section of this pterosaur is preserved, including smashed wing parts.

Sisters to Microtuban

Figure 1. Sisters to Microtuban include No. 42 (more primitive) and Jidapterus (more derived).

Juvenile? No.
The scapula and coracoid are unfused and the extensor tendon process includes a large suture. Elgin and Frey (2011) considered these to be ontogenetic signals that inferred the specimen was a juvenile or sub-adult, as in archosauromorphs. Unfortunately this is false. Pterosaurs are lizards and they don’t follow archosauromorph growth patterns. The sister taxa (Fig. 1) all have similar fusion patterns and they are adults.

Africa? No.
Elgin and Frey (2011) considered Microtuban, from the of Early Cenomanian (Late Cretaceous) of Lebanon, “the most complete pterosaur fossil discovered from Africa.” Oops. Lebanon is actually in the Middle East. Minor faux pas.

Phylogenetic Nesting
Elgin and Frey (2011) reported, “The phylogenetic placement of M. altivolans within the Azhdarchoidea [the Tapejaridae, the Thalassodromidae, the Chaoyangopteridae, and the Azhdarchidae] therefore remains uncertain.” They considered it a “thalassodromid/ chaoyangopterid.

Here, in a larger study, Microtuban nests readily at the base of the Azhdarchidae [Jidapterus through Quetzalcoatlus] and was derived from a sister to No. 42. (By the way, in the larger study Chaoyangopterus was not at all related to Thalassodromeus.) The manual phalanx proportions in Microtuban were identical to those of its azhdarchid and protoazhdarchid sisters, none of whom, no matter their size, fused the scapula to the coracoid until Quetzalcoatlus.

A Reduced Phalanx 4
While more primitive than other azhdarchids, wing phalanx 4 was relatively shorter (less than 5% of the total wing finger) in Microtuban, probably because it represents a late-surviving clade member on its own branch. The reduction of phalanx 4 is also found in Sos 2428, the flightless pterosaur, which is another Microtuban sister. I suspect that another sister, Huanhepterus, also had such a short phalanx 4, but no one I know has actually seen the post-crania.

Loss of Phalanx 4 in Other Pterosaurs?
Elgin and Frey (2011) reported that Anurognathus, Beipiaopterus and Nyctosaurus all had only three wing phalanges. This is true only for derived Nyctosaurus. Check it out.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Elgin and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1