SVP 2 – more Quetzalcoatlus post-cranial studies

Padian et al. 2015
describe the post-crania of Quetzalcoatlus (Fig. 1). There are a few confusing comments in this abstract (see below), which I did not edit. I encourage you to translate them yourself as best as you can.

Quetzalcoatlus in dorsal view, flight configuration.

Figure 1. Quetzalcoatlus in dorsal view, flight configuration.

From the abstract
Quetzalcoatlus northropi was named on the basis of a few incomplete post-cranial
bones that suggested a wingspan of 11-13 m; a morph about half this size is represented by numerous bones and partial skeletons, on which most anatomical studies are based. The 9th and 8th cervical vertebrae could pitch dorsally and the 7th pitched ventrally; the 6th and anterior cervicals pitched dorsally. This bend mitigated horizontal compressive load of the neck on the dorsal column. Some lateral movement was possible at all cervical joints. Dorsal movement was restricted to only three or four mid-dorsals and was mainly lateral. The scapulocoracoid could be protracted and retracted in an arc of about 25°, allowing the glenoid to move anterodorsally and posteroventrally. The humerus could have rotated in the glenoid about 25°; elevated about 45°, and depressed about 25-35°. When soaring, the distal humerus would have been about 20° above the horizontal, and the distal radius and ulna about 15° below it. The angle at the elbow in dorsal view would
have been about 115°. The humerus could move no more than 3-5° anterior to the shoulder, at which point vertical mobility is limited to about 5° above the horizontal and about 10° below it. When the humerus is fully pronated, protraction-retraction is limited to 40-45°. Oriented approximately laterally, the humerus could be elevated above the horizontal about 35°. The radius and ulna could flex to about 75° at the elbow but no rotation [pronation/supination] was possible at either end. When flexed, the radius slid distally over the ulna and retracted the wrist and outboard bones up to 60° (depending on the humeral position). Very limited rotation of the wing metacarpal against the distal syncarpal was possible. The asymmetrical distal ‘pulley’ joint of the wing metacarpal depressed the wing-finger during retraction. All joints of the hind limb are hinges except the hip, a ball-and-socket offset by a neck oriented dorsally, medially, and posteriorly. The hind limb was positioned in walking as in other ornithodirans*, and whether it could be elevated and retracted into a batlike pose incorporated into a hypothetical uropatagium is questionable.”

*a diphyletic taxon.

This abstract feels like
an engineer, in this case, probably J. Cunningham, wrote it, which is good. The reconstruction at reptileevolution.com (Fig. 1) agrees with this description, including the elevation of the elbows in flight, which is rarely done in illustrations and models. There is no trouble elevating the hind limbs into the plane of the wing with those ball and socket joints at the acetabulum. Quetzalcoatlus is often compared to a small airplane in size. Like all pterosaurs it would have also flown like a small airplane, with horizontal stabilizers.

Do not follow the reconstructions of some workers
who overextend the elbows and wrists.

References
Padian K, Cunningham JR and Langston WA (RIP) 2015. Post-cranial functional morphology of Quetzalcoatlus (Pterosauria: Azhdarchoidea) Journal of Vertebrate Paleontology abstracts.

 

Advertisements

SVP 1 – Quetzalcoatlus and Azhdarchids

This post begins a review of select SVP abstracts from the recent convention.

Andres and Langston (2015 abstract)
limit the number of taxa referred to azhdarchidae (Quetzalcoatlus + Azhdarcho) to Turonian (Early Late Cretaceous, 90 mya) taxa using phylogenetic analysis. By definition and age that includes Zhejiangopterus (81 mya) as earlier work by Andres and Myers (2013) did so as well. I’m glad someone is continuing the work started by Wann Langston (RIP). Although the Andres tree is ripe with problems, this node is not a problem.

Azhdarchids and Obama

Figure 1. Click to enlarge. Here’s the 6 foot 1 inch President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our President.

From the abstract
“Over the past 30 years, [the azhdarchidae] has had hundreds of fragmentary specimens referred to it, spanning over 85 million years from the Late Jurassic to the latest Cretaceous. Newly described material of Azhdarcho and Quetzalcoatlus combined with a phylogenetic analysis of referred azhdarchid specimens, allows better resolution of the evolutionary relationships and history of the azhdarchid pterosaurs.”

“The earliest reported occurrences of azhdarchids in the Late Jurassic and Early Cretaceous are of ctenochasmatoids. [not sure which taxa Andres and Langston refer to here]. Despite a tendency to refer most Late Cretaceous pterosaur material to the Azhdarchidae, the clade only dates back to the Turonian. A tapejarid, ornithocheiran, thalassodromine, and the pteranodontids also survive to the early Late Cretaceous. Most of the specimens previously referred to the Azhdarchidae, but now recovered outside of the group, are on the azhdarchid branch as non-azhdarchid neoazhdarchians {again, which taxa?]. These specimens range from the Aptian, when the lineage would have split from the chaoyangopterids at the latest, to the latest Cretaceous, and so comprise the last surviving pterosaurs along with the Azhdarchidae and one Nyctosaurus specimen. The giant and smaller morphs of Quetzalcoatlus are recovered as sister taxa and so are closely related as either a single species or sister species.”

In the large pterosaur tree, there is a continuous lineage in the ancestry of azhdarchid pterosaurs going back to a sister to Huehuecuetzpalli (a basal tritosaur) and Macrocnemus (Middle Triassic tritosaur). Quetzalcoatlus and the azhdarchids were derived from a sister to Zhejiangopterus, Chaoyangopterus, Microtuben, Jidapterus, Sos 2428 (the flightless pterosaur), tiny B St 1911 I 31, CM 11 426, Ardeadactylus (which gave rise to Huanhepterus), Beipiaopterus, tiny and short legged TM 10341 and the SMNS 50164 specimen attributed to Dorygnathus (Fig. 1, Middle Jurassic). Nowhere in this lineage are any ctenochasmatoids, although Huanhepterus has been mistakenly referred to that clade.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 2. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen. These specimens demonstrate isometric growth in pterosaurs – which is heretical as these specimens are conveniently overlooked by the data deniers among pterosaur workers. 

This clade of pre-azhdarchids is remarkable
for demonstrating isometry during ontogeny in Zhejiangopterus (Fig. 2) and isometry during phylogeny starting with long-legged and long-necked B St 1911 I 31 (Fig. 3).

Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog)

Figure 3. Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog). Note the scale bar and the azhdarchid-like proportions in this tiny Late Jurassic azhdarchid precursor.

Brian Andres is the third of three pterosaur workers to have their cladogram of pterosaur phylogeny published on Wikipedia. Although all three have a similar topology (they all retain “The Pterodactyloidea”) at certain nodes, none have a similar topology in the broad sense. None include fenestrasaurs as outgroup taxa. None include several species (distinct specimens) from single genera and and none include the tiny pterosaurs found in the large pterosaur tree. As we learned earlier, phylogenetic miniaturization marked the genesis of several pterosaur clades, so the tiny pterosaurs are key to understanding phylogenetic relationships. We looked at the tree of Andres and Myers (2013) earlier here.

References
Andres B and Langton W 2015. Morphology and phylogeny of Quetzalcoatlus (Pterosauria: Azhdarchidae) Journal of Vertebrate Paleontology Abstracts 2015. 

Stalking or wading azhdarchids (part 3)

Witton and Naish (2013) proposed a terrestrial stalking mode of operation for azhdarchid pterosaurs (Fig. 1). We looked at various aspects of that earlier here and here. Today, a few more details need to be considered.

Figure 1. Click to enlarge. On right from Witton and Naish 2013. On left reconstruction from Cai and Wei 1994 of Zhejiangopterus.

Figure 1. Click to enlarge. On right from Witton and Naish 2013. On left reconstruction based on data from Cai and Wei 1994 of Zhejiangopterus. Compare right stalking image with figure 3 wading image. Consider the great weight of that big skull on the end of that long skinny neck supported by those tiny fingers. All those problems are solved when wading (Fig. 3).

The following notes are retrieved from the boxed captions surrounding the Witton and Naish image (Fig. 1), which you can enlarge to read. 1. Reclined occipital face – Head perpetually angled towards ground when neck is lowered. – True of all wading pterosaurs and most pterosaurs in general. 2. Neck anatomy and arthrology – Long neck reduces effort to produce large movements; range of motion allows easy access to the ground. – True of all wading pterosaurs and most pterosaurs in general. 3. Skull shape and hypertrophied jaw tips – Skull morphology most similar to terrestrial feeding generalists, such as ground hornbills and modern storks; jaw elongation reduces neck action required to reach ground level – True of all wading pterosaurs and most pterosaurs in general.

Figure 3b. Zhejiangopterus fingers. Witton and Naish want you to believe that these three fragile fingers on three spaghetti-thin metacarpals are suitable weight-bearing bones - OR that mc4 is a weight-bearing bone. Neither is true. Metacarpal 4 NEVER makes an impression. The wing finger NEVER makes an impression. They were both held above the substrate in ALL pterosaurs.

Figure 2. Zhejiangopterus fingers. On left based on Cai and Wei 1994. On the right, according to Witton and Naish who want you to believe that these three fragile fingers on three spaghetti-thin metacarpals are suitable weight-bearing bones – OR that mc4 is a weight-bearing bone. Neither is true. Metacarpal 4 NEVER makes an impression. The wing finger NEVER makes an impression. They were both held above the substrate in ALL pterosaurs. The Witton Naish metacarpal is over rotated in order to allow fingers 1-3 to hyper-extend laterally, but that means the wing finger also opens laterally, not in the plane of the wing! Their mc 1-3 are pasted against mc 4, dorsal sides to dorsal side following the false Bennett model. Their fingers don’t match ichnites.

4a. Large coracoid flanges: distally displaced crests. Enlarged anchorage and increased lever arm for flight muscle; powerful takeoff ability. – Actually azhdarchids have relatively small pectoral complexes and small humeri. Witton and Naish employed a juvenile sample for their humerus. 4b. Enlarged medial wing length, decreased wing finger length. Increased forelimb stride; enlarged medial wing region and greatest lift; reduced risk of snagging wingtips on vegetation. – This is also true of all wading bottom feeders, and most pterodactyloid-grade pterosaurs in general. Also note that these traits are present in tiny Solnhofen pterosaurs (Fig. 3). Decreased wing finger length reaches a nadir in JME SOS 2482, a flightless pterosaur with a big belly and definitely NOT a stalker of terrestrial vertebrates.  5. Robust digit bones. Adaptations to weight bearing. – Obviously not true. The free fingers of Zhejiangopterus are both small and gracile and have no obvious adaptation to weight bearing. So, why are they bearing nearly all the weight of Zhejiangopterus (Fig. 1) in the Witton and Naish reconstruction? Instead, think of pterosaur forelimbs like ski poles, good for steadying (Fig. 3), especially while feeding in moving waters (Fig. 4. All weight bearing runs through the hind limb. Here is a Zhejiangopterus matched to tracks (Fig. 3). Witton and Naish make no effort to match a manus and pes to the tracks they use. 

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 3. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

6. Elongate femur (>1.6 humeral length). Increases stride efficiency; decreases attitude of axial column during feeding. In azhdarchids the femora is not relatively longer than in precursor taxa. The humerus is relatively shorter than in most pterosaurs and shorter than azhdarchid precursors like n42 in particular (Fig. 4). The torso is also relatively shorter, but this is also true of tiny precursor azhdarchids, like n42.  l7. Narrow-gauge trackways (Haenamichnus). Sub-vertical limbs providing efficient carriage when walking. – The Witton and Naish drawing overlooks the shallow angle of the femoral head relative to the shaft that would have produced a relatively sprawling, lizard-like femoral angle, as preserved in situ. Even so, the ankles would have remained below the body so long as the knees were below the acetabulum. It is also clear that pterosaur knees were bent during terrestrial locomotion, as in virtually all tetrapods.  8. Compact, padded pes and manus. Maximizes outleaver forces during step cycle; cushioning and increased traction on firm ground. – Witton and Naish based this claim on such loose and sloppy ichnites that individual toes were not distinct. Pads are also not distinct other than in the original drawing. When you look at the actual pes of Zhejiangopterus (Fig. 1) the metatarsus is indeed compact, narrower than in all other pterosaurs. 

Quetzalcoatlus scraping bottom while standing in shallow water.

Figure 4. Quetzalcoatlus scraping bottom while standing in shallow water. Note the attempt here to shift weight posteriorly while the neck is extended anteriorly. Keeping the wing finger close to the forelimb reduces the exposed wing area, important for underwater stability. The air-filled skull is weightless when in water. Not so when terrestrial stalking.

If, on the other hand, azhdarchids were waders, as were their tiny ancestors, like n42 (Fig. 5), then we can see not only their original tall, thin, morphology and their gradual evolution to great size while maintaining their wading niche (Fig. 5), but also a reason for getting bigger; gradually deeper water access. Unfortunately, Witton and Naish make no attempt to nest azhdarchids phylogenetically and certainly make no reference to their tiny ancestors.

Sisters to Microtuban

Figure 5. Sisters to Microtuban include No. 42 (more primitive) and Jidapterus (more derived).

The actual trackmaker of Haenamichnus had fingers (digits 1-3) as long as its foot. That is not found in Zhejiangopterus, but is found in Jidapterus (Fig. 5), a precursor azhdarchid.

Azhdarchids and Obama

Figure 6. Click to enlarge. Here’s the 6 foot 1 inch President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our President. This image replaces an earlier one in which a smaller specimen of Zhejiangopterus was used.

We already have pterosaurs that could have been terrestrial stalkers, like ground hornbills. We call them germanodactylids (Fig. 7). And THEY have horny/bony crests and a sharp, dangerous beak like a hornbill!

Germanodactylus and the Dsungaripteridae

Figure 7. Germanodactylus and the Dsungaripteridae. Click to enlarge. If any pterosaurs were like ground hornbills, these even had horn bills!

The beak tip of azhdarchids is a better pick-up tweezers than a stabbing knife. Better for picking up defenseless invertebrates than for stabbing terrestrial prey capable of fighting back or running away. Remember, when you go back further in azhdarchid phylogeny, you come to dorygnathids, a clade that also gave rise to wading ctenochasmatids. The devil is in the details Witton and Naish give us a pterosaur metacarpus with the false Bennett configuration (Fig. 8) in which metacarpals 1-3 are rotated as a set, like a closed draw bridge, against the anterior (formerly dorsal) surface of mc 4. That provides no space for all four extensor tendons. Now to get those fingers to hyper-extend laterally, Witton and Naish over rotate mc4 by another 90 degrees (Fig. 2). But now their wing opens laterally, no longer in the plane of the wing, as all fossils indicate.

Pterosaur finger orientation in lateral view

Figure 8. Pterosaur finger orientation in lateral view, the two hypotheses. On the left the Bennett hypothesis. On the right the Peters model that is supported by all fossil pterosaurs. These images graphically show how gracile metacarpals 1-3 were and why they could not support the weight of the pterosaur during terrestrial locomotion. The Bennett migration of the metacarpals is another problem. Witton and Naish take the Bennett mc4 one step further by rotating it another 90 degrees in order to produce lateral finger impressions. during hyperextension.

Witton and Naish give us a metacarpus and wing finger that should impress the substrate, but no pterosaur ichnite ever shows an impression of mc4 or the wing finger. So we know those two elements were held aloft during terrestrial locomotion, no matter how much Witton and Naish (and others see figure 9) wish otherwise. Witton and Naish give us a pteroid (Fig. 2) articulated to the preaxial carpal (another Bennett mistake) when the pteroid actually articulates with the radiale. Only soft tissue connects the pteroid and preaxial carpal. Witton and Naish give us pterosaur free fingers that don’t match tracks and don’t match bones. Witton and Naish illustrated from their imagination, both in shape and orientation. Witton and Naish currently hold court on pterosaur morphology, but I think you’ll agree they do so with false reconstructions. These two need to adopt strict and precise standards in which the bones agree with the ichnites and vice versa. Witton and Naish support the forelimb launch in all pterosaurs including giant Quetzalcoatlus. Considering the strain that would run through the three tiny fingers and three slender metacarpals, why do so many smart people take this idea seriously? Earlier we noted the morphological falsehoods artists added to the hand of an anhangueird pterosaur (Fig. 9) to make their forelimb launch hypothesis more logical and appealing by reducing the three free fingers and hoping the giant mc4 and wing finger made an impression in the substrate — but they don’t.

Errors in the Habib/Molnar reconstruction of the pterosaur manus

Figure 9. Errors in the Habib/Molnar reconstruction of the pterosaur manus. This manus uses the false Bennett reconstruction adopted by Witton and Naish and shortens the fingers. Corrections are provided in the lower images.

BTW I’m not blackwashing ALL of the output of Witton and Naish, just the above dozen or so problems. References Witton M and Naish D 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”? Acta Palaeontologica Polonica. available online 28 Oct 2013 doi:http://dx.doi.org/10.4202/app.00005.2013

Walking azhdarchid movie matched to pterosaur tracks

Earlier Pterodactylus, a small pterodactylid pterosaur, was animated to match Craysaac tracks (Fig. 1). In this model the backbone is elevated higher here than in some of the wireframe pterosaurs you may have seen (Fig. 3) and the forelimbs carry little if any of the weight. Nevertheless, in this species they work like and impress like ski poles — doing the pterosaur walk.

Pterodactylus walk matched to tracks according to Peters

Figure 6. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

Today, Zhejiangopterus (Cai and Wei 1994), a large azhdarchid pterosaurs, is similarly animated to match large Korean pterosaur tracks (Hwang et al. 2002; Fig. 2).

Note how Zhejiangopterus carries its head, with the middle ear region above the center of gravity, like a human. At any point Zhejiangopterus could lower its skull for a meal or a drink. It could also raise its wings without shifting its balance to initiate a bipedal takeoff. Note how little the forelimbs actually touch the substrate. Again, this is the ski-pole hypothesis in which the forelimbs are used mainly to steady the pterosaur, not to generate thrust or support the weight (exception noted below).

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.) The feet are planted just as the hands are lifted. Click to enlarge and animate if not moving.

The troubles with the horizontal backbone model are at least threefold

  1. The skull would be far from the center of gravity at the end of a long neck. Bearable, perhaps, in tiny Pterodactylus. unwieldy on giant Zhejiangopterus with its oversized skull.
  2. The forelimbs would bear most of the weight with the skull far beyond them. This is fine when floating and poling.
  3. Standing up to open the wings for display or flight would involve throwing the skull backward to end up standing bipedally. Awkward. Time consuming. The competing quad launch hypothesis is out of the question as reported earlier here and elsewhere for the reasons listed therein.
Figure 3. The horizontal backbone hypothesis for quadrupdal pterosaurs. This hypothetical model is supposed to match tracks, but the tracks can be matched to a genus and species, so why not use it?

Figure 3. The horizontal backbone hypothesis for quadrupdal pterosaurs (Mazin et al. 2009). This hypothetical model is supposed to match tracks, but the tracks can be matched to a genus and species, so why not use it? Click to enlarge. Note the massive bending of the wrist here. Completely unnecessary. 

Mazin et al. (2009) published a series of imagined wireframe pterosaurs matched to the tracks (Fig 3). This is odd because a former champion of bipedal pterosaurs was co-author Kevin Padian, who was a quad ptero-track denier for many years until the Craysaac tracks won him over (while continuing to deny the pterosaur nature of other tracks. Odder still because the animation that was used for the public (which I saw year ago and not sure if it is still in use, but is not used here) showed a more upright Pterodactylus.

Note: The published wire frame model might match the gait and placement of the ptero tracks, but the manus and pes of the wireframe model are but a small fraction of the size of the tracks. This is something the authors and their referees missed, or overlooked. But we all know, the devil is in the details.

“If the glove doesn’t fit, you must acquit.” — Johnny Cochran at the OJ Simpson murder trial.

And if the feet and hands don’t match,
you’ve got the wrong wire frame pterosaur model. Contra Mazin et al., I took the effort to match the manus and pes track to an extinct taxon. In Science, you must use the data as precisely as you can, and let those data tell you, as closely as possible, how to build your model. Don’t walk in with your pet hypothesis and try to shoehorn or BS your way through it, unless you can get away with it, as Mazin et al. did until now.

Figure 4. Zhejiangopterus at a stage in its walking cycle in which the right manus bears nearly all the weight.

Figure 4. Zhejiangopterus at a stage in its walking cycle in which the right manus bears nearly all the weight. M. Habib noted the arm bones were much stronger than they needed to be for flight. Well, maybe that’s because Zhejiangopterus was walking on its forelimbs. Birds don’t do that. BTW that’s the same force vector Habib imagined for his ill-fated quad takeoff. I hate to say it, but this pose makes more sense in every way.

If my model of pterosaur walking is correct,
and I’m sure it has minor flaws that may never be known, then the tiny manus bears nearly the entire weight of the pterosaur at one and only one brief point in the step cycle (Fig. 4) that does not need support in normal bipedal walking. The tiny area of the tiny fingers is likely to impress deeper because the weight of the pterosaur is concentrated on a smaller area (compared to the long foot) in contact with the substrate. This pose also might answer Mike Habib’s original mystery as to why the pterosaur humerus was built stronger than it needed to be for flight. Birds don’t put their weight on the forelimbs. And few bats do (the tiny vampire is the exception).

Here are the alternative models 
for pterosaur quadrupedal standing (Fig. 5) for ready comparison. Which of these provides a bended knee with the proper vectors for thrust? The manus doesn’t have to and didn’t provide thrust, but it should not have been placed so far forward that it could only provide a braking vector to the shoulder.

Click to enlarge. Averinov re-published images of Zhejiangopterus and Quetzalcoatlus from Witton 2007 and Wittion & Naish 2008 that demonstrate a certain devil-may-care attitude toward the anatomy, especially in Quetzalcoatlus. There was little regard for the the shape of the pelvis in both images and little regard for the lengths of the cervical elements and robust pectoral girdle in Q. My images, on the other hand, were traced from photos taken during a visit to Texas several years ago.

Figure 5. Click to enlarge. Averinov re-published images of Zhejiangopterus and Quetzalcoatlus from Witton 2007 and Wittion and Naish 2008 that demonstrate a certain devil-may-care attitude toward the anatomy, especially in Quetzalcoatlus. Moreover, just imagine the long lever problems these two have with that long extended neck while walking and the tremendous strain put on that forelimb, which is not angled correctly to provide thrust. It don’t provide thrust in the more upright pose either, but it doesn’t need to. In that case it merely provides some stability.

On the other hand, a feeding pterosaur in water might have looked something like this (Fig. 6).

Quetzalcoatlus scraping bottom while standing in shallow water.

Figure 6. Quetzalcoatlus scraping bottom while standing in shallow water. Here the hollow and airy skull is nearly weightless or even buoyant in water. 

 

References
Cai Z and Wei F 1994. On a new pterosaur (Zhejiangopterus linhaiensis gen. et sp. nov.) from Upper Cretaceous in Linhai, Zhejiang, China.” Vertebrata Palasiatica, 32: 181-194.
Hwang K-G, Huh M, Lockley MG, Unwin DM and Wright JL 2002. New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea. Geology Magazine 139(4): 421-435.
Mazin J-M, Jean-Paul Billon-Bruyat J-P and Padian K 2009. First record of a pterosaur landing trackway. Proceedings of The Royal Society 276:3881–3886.
online pdf 
Unwin D and Lü J. 1997. 
On Zhejiangopterus and the relationships of Pterodactyloid Pterosaurs, Historical Biology, 12: 200.

wiki/Zhejiangopterus

Eurazhdarcho and LIPB R 2.395: two new azhdarchid pterosaurs

Two European azhdarchids
have become known recently. Eurazhdarcho langendorfensis EME VP 312/2 (Vremir et al. 2013, Fig. 2) and the unnamed LIPB R 2.395 (Vremir et al. 2015. Fig. 1). Eurazhdarcho is known from a distal mc4, a proximal m4.1 and a proximal mt3 (not a distal mc3 as originally labeled, see below), plus cervicals 3 and 4. LIPB R 2.395 is known from a cervical 4 only.

What little is known indicate that both are similar in size and proportions to Zhejiangopterus. And they are just as gracile.

Figure 1. LPB-(FGGUB)-R.2395 cervical 4 with other cervicals imagined.

Figure 1. LPB-(FGGUB)-R.2395 cervical 4 with other cervicals imagined.

The re-identification
of distal metacarpal 3 in Eurazhdarcho (Figs. 2, 3) as metatarsal 2, 3 or 4 is based on the shape of the bone in question. It is expanded asymmetrically proximally and flattened as preserved in situ in Eurazhdarcho (Figs 2, 3) and Quetzalcoatlus (Fig. 4). By contrast distal metacarpal 3 in all pterosaurs has a convex articular surface to accommodate an unrestricted metacarpophalangeal 3 joint permitting extreme extension for implanting posteriorly while walking.

Figure 2. Eurazhdarcho with mc3 reidentified as mt3.

Figure 2. Eurazhdarcho with distal mc3 (in red and in figure 3) re-identified here as proximal portion of metatarsal 2, 3 or 4.

The in-situ placement
of the bone in question (Fig. 2) on the fossil near metacarpal 4 cannot be valid evidence because the cervicals are also extremely displaced. These bones became a jumbled mess long after the body had disintegrated and these few scattered elements were fossilized.

Figure 3. Close up of bone labeled distal mc3. This looks more like proximal mt3.

Figure 3. Close up of bone labeled distal mc3 in Eurazhdarcho. This looks more like a proximal metatarsal in Quetzalcoatlus in figure 4. There is no spherical articulation surface here that would indicated a distal metacarpus. The pink area is a restoration that could represent a much longer distal metatarsal.

The metatarsus of Quetzalcoatlus (Fig 4)
provides comparable data for the Eurazhdarcho bone in question. Metatarsal 4 is shown because it shows better on the lateral edge of the foot. Metatarsal 3 lies beneath it. Both appear to be a good match.

Figure 3. Metatarsal 3 in Quetzalcoatlus looks like the same bone in Eurazhdarcho labeled as a distal metacarpal 3.

Figure 4. Metatarsal 3 in Quetzalcoatlus looks like the same bone in Eurazhdarcho labeled as a distal metacarpal 3. Click to enlarge.

Good to see
mid-sized azhdarchids in eastern Europe to go with the giant Hatzegopteryx, also known from scraps.

I sincerely hope
one of the authors of both papers, Darren Naish, is not too upset by this reinterpretation. We’ve heard from him before. I confess: I used DGS. Never saw the actual fossil. And I don’t have a PhD. Did I make a mistake? Let me know and a change will be made.

References
Vremir MTS, Kellner AWA, Naish D, Dyke G 2013. Laurent  V, ed. A New Azhdarchid Pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: Implications for Azhdarchid Diversity and Distribution. PLoS ONE 8: e54268.
Vremir MTS, Witton M, Naish D, Dyke G, Brusatte SL, Norell M and Totoianu R 2015. A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania). American Museum Novitaes 3827 16 pp.

 

Evidence for a flightless Quetzalcoatlus northropi

Quetzalcoatlus northropi (Fig. 1, Lawson 1975) is well known as the largest pterosaur of all time. It is known chiefly from most of the wing, which dwarves that of the more complete specimen of Q. sp. (Kellner and Langston 1996), which was found a mere 40km away from sediments of a similar age (Latest Cretaceous). Other giant azhdarchid pterosaurs competing for “the largest pterosaur of all time” are known from less complete remains.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 1. Click to enlarge. Quetzalcoatlus specimens to scale. Here Q. northropi is 2.5x taller than Q. sp, if nothing else changed other than size. 

Some workers (Henderson 2010) have questioned the flying abilities of Q. northropi. Others (Witton and Habib 2010) have given it tremendous flying abilities, able to soar between continents. Both have relied on scaling the small specimen up to the size of the giant.

I was curious
to compare the large and small specimens. Several years ago I took photos of the large specimen wing at the Langston lab in Austin, Texas. The tracings of the large specimen were scaled down to the size of the small specimen (Fig. 2). They are — almost  — identical.

Figure 1 Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn't make sense if Q. northropi was volant.

Figure 2. Quetzalcoatlus sp. compared to the large specimen wing, here reduced to match that of the smaller specimen. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. Note m4.2 is narrower and shorter on the larger specimen, which doesn’t make sense if Q. northropi was volant. It might have been shorter still if Option 1 is valid. At this point, either is possible. 

Scaling pterosaurs helps one understand some of the “big” questions. Everyone knows that to double the height of the animals is to cube its weight. The same holds true for pterosaurs. So then we might ask, if the larger specimen had higher wing loading, why wasn’t the wing spar more robust? As you can see, the wing elements were not more robust in the giant — AND — m4.2 was more gracile (Fig. 2).

The answer to that question is not so obvious, as we learned before. The proportions of giant azhdarchids were quite similar to those of the tiniest proto-azhdarchids, as you can see below (Fig. 3).

We also see distal wing phalanx reduction in the evolution of the flightless pterosaur, Sos 2428 from tiny ancestors, n42, and n44 (from the Wellnhofer 1970 catalog, Fig. 3) with longer wings.

Figure 2. The flightless pterosaur, Sos 2428, along with two ancestral taxa, both fully volant. Note the reduction of the wing AND the expansion of the torso. We don't know the torso of Q. northropi. It could be small or it could be very large.

Figure 3. The flightless pterosaur, Sos 2428 to scale along with two ancestral taxa, both fully volant. Note the reduction of the wing AND the expansion of the torso. We don’t know the torso of Q. northropi. It could be small or it could be very large.

Here in the flightless pterosaur (Fig. 3), perhaps more importantly, the torso expanded greatly in every direction during the evolution of flightlessness. The pelvis was also much larger in Sos 2428.

We don’t have enough torso material from the Quetzalcoatlus northropi specimen to understand its volume. While it is possible that the torso remained small, as in Q. sp. (Fig. 1), it is equally possible that it could have expanded to become voluminous, as in Sos 2428.

Until we know, we can only guess, but the relative reduction of the distal wing elements, beyond what we see in the smaller specimen, adds weight to the argument that flight was more difficult for the giant.

More data would help settle this issue.
We take our clues wherever we can. Don’t overlook the little stuff.

References
Henderson DM (2010). Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30(3):768-785.
Kellner AWA and Langston W 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from late Cretaceous sediments of Big Bend National Park, Texas. – Journal of Vertebrate Paleontology 16: 222–231.
Lawson DA 1975. Pterosaur from the latest Cretaceous of West Texas: discovery of the largest flying creature. Science 187: 947-948.
Witton MP and Habib MB 2010. On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. PlosOne 5(11): e13982. doi:10.1371/journal.pone.0013982

wiki/Quetzalcoatlus

 

 

Was Hatzegopteryx flightless?

Figure 1. Hatzegopteryx elements to scale with the more completely known Quetzalcoatlus sp. and Quetzalcoatlus northropi (largely hypothetical). Scaling up Q. sp. to the size of Quetzalcoatlus puts the humerus to the size of Q. northropi and Hatzegopteryx (based on the partial humerus). However the skull of Hatzegopteryx, based on the pterygoid/quadrate is both much wider and much longer than the scaled up Q. northropi skull. A bigger skull means a more robust neck for Hatzegopteryx -- which gives it less of a chance of flying. Zhejiangopterus and Azhdarcho also shown to scale.

Figure 1. Hatzegopteryx elements to scale with the more completely known Quetzalcoatlus sp. and Quetzalcoatlus northropi (largely hypothetical). Scaling up Q. sp. to the size of Quetzalcoatlus puts the humerus to the size of Q. northropi and Hatzegopteryx (based on the partial humerus). However the hypothetical skull of Hatzegopteryx, based on the pterygoid/quadrate is both much wider and much longer than the scaled up Q. northropi skull. A bigger skull means a more robust neck for Hatzegopteryx, etc. etc.  — which gives it less of a chance of flying due to its greater mass and no greater humerus. Zhejiangopterus and Azhdarcho also shown to scale. Zhejiangopterus also has a relatively larger skull and smaller humerus, but has no other flightless traits, like a large torso or robust skeletal elements.

Fun with scale bars
Based on the humerus, Hatzegopteryx (Buffetaut et al. 2003, Fig. 1) was no larger than Quetzalcoatlus northropi (Lawson 1975), one of the largest pterosaurs of all time. However, based on the pterygoid / quadrate and jugal (Fig. 1), Hatzegopteryx was much larger (if the skull and rostrum had similar proportions to Q. northropi), based on the scale bars.

We have a good narrow mandible for Q. sp. (Kellner and Langston 1996). We also have its palatal elements. The pterygoid and humerus are the only bones both taxa share in common. These few elements, along with the scale bars, form the basis for these largely hypothetical reconstructions and restorations (Fig. 1).

Flightless?
It’s hard to figure out what the rest of the pterosaur looked like based on just a few palatal bones. But it appears that the much larger skull of Hatzegopteryx might tip the scales toward flightlessness. If so, Hatzegopteryx would not be the first flightless pterosaur known. That honor goes to JME Sos 2428 (Peters 2013), a Late Jurassic protoazhdarchid.

That robust jugal counts too.
The jugal of Hatzegopteryx was not a fragile, slender bone, but a robust one, according to Buffetaut et al. (2002). So Hatzegopteryx was not trying to save weight by having paper thin bones.

Wikipedia reports, “In Hatzegopteryx, the skull bones are stout and robust, with large-ridged muscle insertion areas. In their 2002 description, Buffetaut and colleagues suggested that in order to fly, the skull weight of this pterosaur must have been reduced in some unconventional way (while they allowed that it could have been flightless, they found this unlikely due to the similarity of its wing bones to flying pterosaurs). The authors theorized that the necessary weight reduction was accomplished by the internal structure of the skull bones, which were full of small pits and hollows (alveoli) up to 10 mm long, separated by a matrix of incredibly thin bony struts (trabeculae), a feature also found in some parts of Hatzegopteryx wing bones. The authors pointed out that this unusual construction, which differed significantly from the irregular internal structure of other pterosaur skulls, resembles the structure of expanded polystyrene, the substance used to make Styrofoam. They noted that this would allow a sturdy, stress-resistant construction while remaining lightweight, and would have allowed the huge-headed animal to fly.”

More on Hatzegopteryx
Hatzegopteryx was found in the upper part of the Middle Densus-Ciula Formation (Upper Cretaceous, Late Maastrichtian). Holotype (FGGUB R 1083): fragments of a skull and associated partial humerus. Referred material: Femur (FGGUB R 1625).

Figure 2. Hatzegopteryx humerus restored to follow Quetzalcoatlus northropi.

Figure 2. Hatzegopteryx humerus restored to follow Quetzalcoatlus northropi. Buffetaut et al. did not provide a sufficiently robust shaft compared to the photo.

The humerus was odd
There is no preserved indication of a posterior tuberosity of the humerus, as shown in Quetzalcoatlus and Pteranodon. The cross-section of the shaft near the deltopectoral crest was round, not hollowed out as in Quetzalcoatlus and Pteranodon. There is no indication of a typical shoulder joint, as in flying pterosaurs. Those parts may be worn away.

Figure 3. Click to enlarge. Hatzegopteryx palate elements added to Quetzalcoatlus species elements and vice versa. The basipterygoids have not been documented in azhdarchids or sister taxa, but appear to be paired rather than single, as Buffetaut et al. proposed.

Figure 3. Click to enlarge. Hatzegopteryx palate elements added to Quetzalcoatlus species elements and vice versa. The basisphenoids have not been documented in azhdarchids or sister taxa, but appear to be paired rather than single, as Buffetaut et al. proposed. Paired elements are primitive and are found in Dorygnathus, the closest known sister with these elements visible.

The basisphenoid(s)
The basisphenoids in basal pterosaurs are paired and connect the braincase to the quadrate/pterygoid suture. In certain derived forms the basisphenoids merge. Buffetaut et al. imagined that they merged, as they do in Pteranodon, but no azhdarchid shows that and the base of the occiput appears to have paired basisphenoid breaks, not a single one. Pteranodon had a much narrower occiput, more appropriate for a single basisphenoid.

References
Buffetaut E, Grigorescu D and Csiki Z. 2002. A new giant pterosaur with a robust skull from the latest Cretaceous of Romania. Naturwissenschaften, 89(4): 180-184.
Buffetaut E, Grigorescu D and Csiki Z 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (Western Romania). In: Buffetaut E, Mazin J-M, eds. Evolution and Palaeobiology of Pterosaurs, Geological Society of London, Special Publication, 217, (2003) pp 91–104.
Kellner AWA and Langston W 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from late Cretaceous sediments of Big Bend National Park, Texas. – Journal of Vertebrate Paleontology 16: 222–231.
Lawson DA 1975. Pterosaur from the latest Cretaceous of West Texas: discovery of the largest flying creature. Science 187: 947-948.
Peters D. 2013. A flightless pterosaur. Journal of Vertebrate Paleontology supplement program and abstracts: 191.

wiki/Hatzegopteryx