New Como Bluff (Latest Jurassic) pterosaurs

Bits and pieces
of new Latest Jurassic pterosaurs are coming out of aquatic deposits in western North America according to McLain and Bakker 2017. The material is 3D and not very mineralized, so it is extremely fragile.

Specimen(s) #1 – HMNS/BB 5027, 5028 and 5029
“One proximal and two distal femora match a complete femur (BYU 17214) referred to Mesadactylus. Unexpectedly, both of the BBF distal femora possess a large intercondylar pneumatopore. BYU 17214 also possesses an intercondylar pneumatopore, but it is smaller than in the BBF femora. Distal femoral pnuematicity is previously recognized only in Cretaceous azhdarchoids and pteranodontids.”

The Mesadactylus holotype and referred specimens reconstructed to match the flightless pterosaur, Sos2428.

Figure 1. The Mesadactylus holotype (Jensen and Padian 1989) nests with the North American anurognathids. Several referred specimens (Smith et al. 2004), when reconstructed nest at the base of the azhdarchidae, with Huanhepterus and the flightless pterosaur SOS 2428.  The new BYU 17214 femur is essentially identical to the femur shown here.

Earlier we looked at two specimens referred to Mesadactylus. One is an anurognathid (Fig. 1). The other is a basal azhadarchid close to Huanhepterus, not far removed from its Dorygnathus ancestors in the large pterosaur tree. Instead McLain and Bakker compare the femora with unrelated and Early Cretaceous Dsungaripterus, which convergently has a similar femur. The better match is to the basal azhdarchid, so distal femoral pneumaticity does not stray outside of this clade. By the way, it is possible that Mesadactylus was flightless.

Specimen(s) #2 – HMNS/BB 5032 (formerly JHU Paleon C Pt 5)
“A peculiar BBF jaw fragment shows strongly labiolingually compressed, incurved crowns with their upper half bent backwards; associated are anterior fangs. We suspect this specimen is a previously undiagnosed pterosaur.”

These toothy specimens were compared to two Early Cretaceous ornithocheirids, one Middle Jurassic dorygnathid, and one Latest Jurassic bird, Archaeopteryx. None are a good match. A better, but not perfect,match can be made to the Early Jurassic pre-ctenochasmatid, Angustinaripterus (Fig. 2) which has relatively larger posterior teeth than does any Dorygnathus specimen.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

As before,
we paleontologists don’t always have to go to our ‘go to’ taxon list of familiar fossils. Expand your horizons and take a fresh look at some of the less famous taxa to make your comparisons. You’ll find a good place to start at ReptileEvolution.com

References
McLain MA and RT Bakker 2017. Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff,
Wyoming, including a pterosaur with pneumatized femora.

Hatzegopteryx: one error in cervical identification leads to trouble

Azhdarchid pterosaurs
as we learned earlier, first achieved their slender proportions in small, sand-piper-like taxa similar to n44 and n42 during the Late Jurassic (Fig. 1). Coeval and later taxa grew larger, some attaining stork-like and then giraffe-like sizes while maintaining their slender proportions.

Azhdarchids and Obama

Figure 1. Click to enlarge. Here’s the 6 foot 1 inch former 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 a human male.

Extant storks are stalkers
whether wading or on firmer substrates. That analogy brings us, once again, to the Naish and Witton 2017 concept of azhdarchids as terrestrial stalkers. They revisit the subject  a third time (after Witton and Naish  2008. 2015), but now freshly armed with the evidence of a large short cervical from Hatzegopteryx, a giant pterosaur from Romania.

The big question is: which cervical is it?

In giant derived azhdarchids.
like Quetzalcoatlus and Hatzegopteryx, half the cervicals (1-3 and 8) are not elongate and the other half (4-7) are elongate.

Unfortunately and earlier
Witton and Naish 2008 mistakenly numbered the cervicals of Phosphatodraco 4-9, when they should have labeled them 3-8 (Fig. 2). They saw that neural spine on #7, which they thought was #8.

Cervical number 8 is always short in azhdarchids
and if correctly identified would have allowed the possibility that Hatzegopteryx had a typical azhdarchid neck. Cervical number 5 is always the longest in giant azhdarchids and Phospatodraco, which gives workers a starting point if the bones are scattered or incomplete at the ends.

But Naish and Witton took it the other way
and with their misidentification of a wide cervical number 7 they imagined a wide cervical series for Hatzegopteryx. And with that they thought they had more evidence for terrestrial stalking instead of aquatic wading, as practiced by all ancestors back to the Late Jurassic. I’m not saying azhdarchids didn’t pick up a few tidbits on land. I am saying they and all their ancestors were built like living sandpipers, stilts and herons, which find their diet in the shallows.

Figure 2. Black images are from Naish and Witton 2017. Cervical series is from Witton and Naish 2008. Purple and red are added here. Improper cervical identity in 2008 led to bigger problems in 2017.

Figure 2. Black images are from Naish and Witton 2017. Cervical series is from Witton and Naish 2008. Purple and red are added here. Improper cervical identity in 2008 led to bigger problems in 2017 where the authors switched real for imaginary in their graphic, which makes it look like they had more data than they really did. BTW, none of these belly-flopping pterosaurs could have taken off in this fashion.

As much as Naish and Witton write about azhdarchids,
they should not be making basic mistakes over and over again. Not only do they misidentify a cervical, they illustrate their pterosaurs doing belly flops in a purported take-off configuration that has no chance of succeeding. See here, here and here for details.) And finally they should no longer consider that pterosaurs had nine cervicals. That goes back to S. Christopher Bennett’s PhD thesis in which he considered vertebrae number 9 to be a cervical since it did not contact the sternum. Even so, it bore long ribs and was located inside the thorax.

Pictured here
(Fig. 3) is the Hatzegopteryx cervical in question. Compared to both Phosphatodraco (Fig. 2) and Quetzalcoatlus sp. (Fig. 3) this is cervical #8, the short one, not cervical #7, the long one.

Figure 3. Hatzegopteryx cervical. If it is number 7, as Naish and Witton suggest, then it is very short and likely would be part of a very short neck. But if it is number 8, then the proportions are typical for azhdarchids. This is where Occam's Razor might have been useful.

Figure 3. Hatzegopteryx cervical. If it is number 7, as Naish and Witton suggest, then it is very short and likely would be part of a very short neck. But if it is number 8, then the proportions are typical for azhdarchids. This is where Occam’s Razor might have been useful.

Some azhdarchids and their kin
have a tall neural spine only on cervical #8. Quetzalcoatlus is in this clade. Some, like Zhejiangopterus and Chaoyangopterus, have no tall neural spines. That’s also the case with the tiny basalmost clade members. By contrast, the flightless pterosaur, JME-Sos 2428 has a tall neural spine on cervicals 6-8, which makes me wonder if Phosphatodraco (Fig. 2) is a sister to it, given the present limited amount of data.

The Domino Effect
When Naish and Witton decided that Hatzegopteryx cervical #8 was #7, that mistake unleashed the possibility that they had discovered the first “short neck” azhdarchid! They must have been excited.

What Naish and Witton did not show you…
In lateral view, the Hatzegopteryx cervicals Naish and Witton illustrated actually look normal for an azhdarchid, but in dorsal view the omitted cervicals would have to have been twice as wide as typical and no longer cylinders (Fig. 2). So the “short” neck was really a “wide flat” neck, but that does not have the same headline cache. Such a major departure from the azhdarchid bauplan should have caused Naish and Witton to reconsider that their ‘discovery’ was actually a simple error in identification, now percolating online for the last 8 years.  Hope this helps quell the notion!

References
Naish D and Witton MP 2017. Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked predators. PeerJ 5:e2908; DOI 10.7717/peerj.2908
Witton MP and Naish D 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLOS ONE 3:e2271 DOI 10.1371/journal.pone.0002271.
Witton MP and Naish D 2015. Azhdarchid pterosaurs: water-trawling pelican mimics or terrestrial stalkers? Acta Palaeontologica Polonica 60:651660 DOI 10.4202/app.00005.2013.

Brian Switek blog
wiki/Hatzegopteryx

Forfexopterus: a Huanhepterus sister

Boy, it’s been a long time
since we’ve looked at a new pterosaur. Several months, perhaps… maybe longer…

Figure 1. Forfexopterus reconstructed. Note the metacarpals: 1>2>3, shared with Ardeadactylus. The rostrum tip is off the matrix.

Figure 1. Forfexopterus reconstructed. Note the metacarpals: 1>2>3, shared with Ardeadactylus. The rostrum tip is off the matrix. Note the difference between the actual fingers and the traced fingers by Jiang et al. The lack of precision in the Jiang et al. tracing, despite it being traced from a photograph, is a little disheartening.

Jiang et al. 2016
present a new disarticulated, but largely complete Early Cretaceous pterosaur, Forfexopterus jeholensis (Figs. 1–3). Jiang et al. consider their new find an ‘archaeopterodactyloid’ based on the ‘long metacarpus and reduced mt5’–but those are convergent traits in four pterodactyloid-grade clades. The large pterosaur tree (LPT) nests Forfexopterus near the base of the azhdarchid clade, which arises from the Dorygnathus clade, specifically nesting between Ardeadactylus and Huanhepterus + Mesadactylus (BYU specimen, not the anurognathid with the same name).

Figure 1. Forfexopterus original tracing, colors added.

Figure 2. Forfexopterus original tracing, colors added. See how simple colors ease the chaos of the roadkill fossil.

Unfortunately 
the Jiang et al. phylogenetic analysis suffers from taxon exclusion. They consider the Archaeopterodactyloidea to be composed of Germanodactylidae, Pterodactylus, Ardeadactylus. Gallodactylidae and Ctenochasmatidae. Those members are only monophyletic if the clade also includes Dorygnathus in the LPT, which was not the intention of the authors. It’s been awhile, but let us recall that the former clade “Pterodactyloidea” had four separate origins in the LPT, two from Dorygnathus (Ctenochasmatidae and Azhdarchidae) and the rest from Scaphognathus which was, in turn, also derived from Dorygnathus through several intervening transitional taxa.

Figure 2. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

Figure 3. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

Forfexopterus
has the slender proportions of Huanhepterus and Ardeadactylus. The rostrum was longer and lightened with several fenestra, one of which was likely a naris. Metacarpals 1–3 were longer medially, the opposite of basal pterosaurs. That trait lines up the joints in m1-3. Manual 4.2 is sub equal to m4.1, unique to this clade and atypical for pterosaurs in general.  Atypical for smaller members of this clade, but typical for larger members (like Jidapterus, but evidently not Huanhepterus (data comes from awkwardly produced original drawing)), the scapula was subequal to the coracoid and would have articulated with a notarium, which is not preserved, or is still largely buried (Fig. 2).

Shorthand suggestion (again)
There are two ways you can label a tetrapod phalanx:

  1. ph3d4 = phalanx 3, digit 4 (manus or pes? as shown in figure 2 above) or
  2. m4.3 = manual 4th digit, 3rd phalanx

Jiang et al. labeled their illustration using #1. You may find that method cumbersome and space consuming. I use and encourage others to use #2, the shorthand version.

When you check out the
Wikipedia page on Forfexopterus, the link to Archaeopterodactyloidea references three papers with Dr. Brian Andres as a co-author including his dissertation on
Sytematics of the Pterosauria. It’s great that PhD candidates tackle large projects. It’s hard work that makes them study their subject and prove their mettle. However, by definition, PhD candidates are not experts. They want to become experts by creating a dissertation, but they come to their projects naive, trusting the literature and beholding to their professors. These are all potential problems, as we talked about earlier.

In like manner, 
for my second paper (Peters 2000) I came to the project naive and trusting the literature. Judging from a vantage point, 17 years later, my observations were not those of an expert. Even so, I hit the mark with regard to pterosaur origins despite the many errors in that paper that have been corrected here and at ReptileEvolution.com. The nesting of pterosaurs apart from archosaurs and close to Macronemus, Tanystropheus, Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama has been validated and cemented by the large reptile tree (LRT). No other candidate taxa have ever been shown to be closer (= produce a gradual accumulation of derived traits). Attempts at correcting the observational errors in academic publications have been rejected by the referees who don’t want any more evidence published that pterosaurs are not dinosaur kin — or that tiny Solnhofen pteros are not babies.

Unfortunately
the Andres dissertation fails to produce a cladogram in which a gradual accumulation of traits can be traced in all derived taxa. For instance, anurognathids are basal to pterodactyloids in the Andres cladogram and the clade Archaepterodactyloidea was recovered. The Andres dissertation shortcoming can be attributed to taxon exclusion. By contrast, the LPT minimizes taxon exclusion by including many specimens ignored by Andres and other prior workers including multiple species within several genera and all those sparrow- and hummingbird-sized Solnhofen specimens. I know pterosaur workers are loathe to admit it, or recognize it, but those extra specimens are key to understanding pterosaur interrelations.

If you don’t look, you’ll never see.
If you don’t ask, you’ll never find out. Fellow pterosaur workers, don’t keep your blinders on. Expand your taxon lists to include a wider gamut of specimens.

This is Science.
When workers publish and referee allow manuscripts to be published they are judging the work fit for print. At that point they have stated their case. If the work stands up to rigorous scrutiny, then it will be cherished. If the work has flaws, then it’s up to fellow workers to expose those flaws for the good of Science.

References
Andres BBB 2010. Systematics of the Pterosauria. Dissertation. Yale University. p. 366.
Jiang S, Cheng X, Ma Y and Wang X 2016. A new archaeopterodactyloid pterosaur from the Jiufotang Formation of western Liaoning, China, with a comparison of sterna in Pterodactylomorpha. Journal of Vertebrate Palaeontology: e1212058.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

wiki/Forfexopterus
wiki/Archaeopterodactyloidea

Azdarchid pterosaurs as terrestrial stalkers? (Again?)

Witton and Naish 2015
once again conclude that terrestrial foraging remains the most parsimonious habit for azhdarchid pterosaurs. (Didn’t we see this earlier in Witton and Naish 2008?) There’s nothing new here. The two professors have put forth the same lame hypothesis seven years later with no apologies for the former and no improvements in the latter.

Unfortunately for Witton and Naish
the best modern analogs, birds that most closely resemble azhdarchid pterosaurs, are all shallow water waders (Fig. 3). That fact/observation has not changed in seven years. To make matters worse, and for reasons known only to themselves, Witton and Naish have set up a straw dog, the pelican for their foil.

Straw dog = In business, something (an idea, or plan, usually) set up to be knocked down. It’s the dangerous philosophy of presenting one mediocre idea, so that the listener will make the choice of the better idea which follows.

Foil = a character who contrasts with another character (usually the protagonist) in order to highlight particular qualities of the other character.

No one thinks azhdarchids resemble pelicans!
What were Witton and Naish thinking?? The key word ‘pelican” is found thirty times in their paper prior to the references. The word “stork” is found nine times. The word ‘hornbill” is found three times. The word “heron” is not found.

Figure 1. Witton and Naish 2015 azhdarchid based on a chimaera of pterosaurs including Zhejiangopterus juvenile for the skull.

Figure 1. Witton and Naish 2015 azhdarchid based on a chimaera of pterosaurs including using a Zhejiangopterus juvenile for the skull. Juvenile skulls are fine because pterosaurs develop isometrically according to ReptileEvolution.com. But Witton and Naish don’t see it that way. They think juvenile pterosaurs have large eyes and a short rostrum, like archosaurs. So, are they straddling the fence? Being hypocritical? Or taking their first steps out of the dark side?

There is no denying
that long-legged, long-necked, long-billed azhdarchid pterosaurs (Figs. 1, 2) most closely resemble today’s similarly built wading storks and herons (Fig. 3). And yet Witton and Naish don’t quite see it that way. Yes, they report that azhdarchid traits were “stork-like.” But, oddly they choose the one stork that does not have an elongate neck, the Marabous stork (Fig. 4, which often wades). SO… they also add in the ground hornbill, which does not wade because it does not have extra-long legs nor an extra-long neck.

Earlier (in 2013) we noted that hornbills most closely resemble similarly short-legged germanodactylids…something that was overlooked by Witton and Naish in 2008 and ignored in 2015.

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.

Once again we trot out
the Zhejiangopterus azhdarchid ontogeny series (Fig. 2) demonstrating isometric growth, but Witton and Naish don’t subscribed to isometry, but rather to allometry. Perhaps hypocritically, and without comment, Witton and Naish used the giant skull of a small juvenile Zhejiangopterus and placed it on the body of an adult specimen. Why didn’t they elongate the rostrum and reduce the orbit to follow their “pterosaurs as archosaurs” hypothesis? They should have, but they didn’t. Actually, I’m glad they did not elongate the rostrum of the juvenile when they put it on the adult body. Apparently Witton and Naish hopped the fence and embraced the hypothesis that was otherwise only found at ReptileEvoluton.com and hoped to that nobody would notice.

As Pterosaur Heresies readers all know…
Pterosaurs, like other lepidosaurs, develop isometrically. Archosaurs go through a short nose “cute” phase known as allometry. You’ll see such short-nosed juvenile pterosaurs throughout the illustrations of Witton, but this is no paradigm shift for him.

The bird genera
that Witton and Naish consider effective analogues for ground-feeding azhdarchids, are the large African stork, Leptoptilos and the ground hornbill, Bucorvus (Fig. 4). I can’t imagine that anyone else agrees, especially when you have better analogs in the saddle-bill stork (Fig. 3), all ready to Google under the keyword, “stork.”

Figure 3. In my opinion this saddle-bill stork wading in water appears to be the bird closest to azhdarchid morphology and, for that matter, niche.

Figure 3. In my opinion this saddle-bill stork wading in water appears to be the bird closest to azhdarchid morphology and, for that matter, niche.

Oddly
Witton and Naish avoid the herons completely. Sure they have a smaller skull, but herons do have a long neck lacking in the birds that Witton and Naish prefer. You just don’t get both huge skull and a long neck in modern birds, otherwise we would note them as modern analogs. Wading azhdarchids were illustrated here in prior blogs.

Figure 4. Two herons, a Marabou stork and a ground hornbill, which is of these birds, the least like an azdarchid. Perhaps that is why one was not pictured in Witton and Naish 2015, despite the manuscript.

Figure 4. Two herons, a Marabou stork and a ground hornbill, which is of these birds, the least like an azdarchid. Perhaps that is why one was not pictured in Witton and Naish 2015, despite the manuscript.

Unfortunately
Witton and Naish still do not indicate the slightest interest in azhdarchid origins (Fig 5). The large pterosaur tree demonstrates their origins in tiny taxa of similar shape. That long neck developed early in their tiny ancestry and was maintained throughout.

Azhdarchids and Obama

Figure 5. 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.

 

Heron damage from spearing a fish

Figure x. Heron damage from spearing a fish. Perhaps this was the preferred technique for the sharp billed germanodactylids, including the nyctosaurs and pterandontids.

A Weapon? Sure!
Witton and Naish describe the use of the long sharp rostrum as a weapon capable of inflicting deep wounds. We looked at that earlier with a photo of a fish after a heron stab.

When you read about Witton and Naish
disrespecting ReptileEvolution.com, remember that they wrote and published two identical papers that overlooked the obvious. They set up a straw dog where one was neither needed nor warranted. They created a chimaera reconstruction. And finally, after blackwashing my work at ReptileEvolution.com, they embraced the use of a juvenile skull on an adult pterosaur.

Perhaps there is still hope
for those two professors! Wonder how they’ll try to backpedal this?

References
Witton MP and Naish D 2008. A Reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271
Witton MP and Naish D 2015. Azhdarchid pterosaurs: water-trawling pelican mimics
or “terrestrial stalkers”? Acta Palaeontologica Polonica 60 (3): 651–660.

SVP 7 – Montanazhdarcho, not an azhdarchid

Carroll 2015 reports
on the North American Late Cretaceous pterosaur, Montanazhdarcho.

From the abstract:
“The latest Cretaceous fossil record of pterosaurs is dominated by azhdarchids, despite various reports of non azhdarchid material from the Late Campanian and Maastrichtian. However, the only indisputable non-azhdarchid pterosaur material from the latest Cretaceous has been the single nyctosaurid humerus from the Gramame Formation of Brazil*. This study presents evidence that Montanazhdarcho minor is a nonazhdarchid member of the Azhdarchoidea**. M. minor was assigned to the Azhdarchidae based on diagnostic features of the humerus, shoulder girdle, and the partial cervical vertebra of the holotype MOR 691. The initial description focused mainly on the diminutive size (2.5 m wingspan). Subsequent discoveries of postcranial material from thallasadromines, tapejarines, and azhdarchids have revealed that the postcranial features initially used to assign M. minor to the Azhdarchidae are synapomorphies for the more inclusive Azhdarchoidea clade. Phylogenetic analysis reveals that Montanazhdarcho possesses multiple characters that are shared by the Tapejarinae and Thallasadrominae: (1) a broad and well-developed tubercle at the ventroposterior margin of the coracoid; (2) a massive, distinct ulnar crest with a developed proximal ridge; (3) a strong boot-like ventral margin of the humeral head; (4) an ulna/radius as long or longer than metacarpal IV; an (5) a phalanx IV-1 that is as long or longer than metacarpal IV. The results of this study show that the Late Cretaceous pterosaur fauna was not entirely dominated by azhdarchids and recognizes important post-cranial characters that better define Azhdarchoidea. The reappraisal of M. minor as a non-azhdarchid member of theAzhdarchoidea also recognizes M. minor as the first known pterosaur of that clade found in North America, as well as one of the latest occurrences of the group.”

*Actually there is a large rostrum that belongs to another tupuxuarid from the Latest Cretaceous of southern Texas (Fig. 1), so it is not surprising to find tapejarid material then and there.

TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 1. TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It’s a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

** Azhdarchoidea improperly includes tapejarids. In the large pterosaur tree the azhdarchids are derived from dorygnathids while the tapejarids are derived from germanodactylids.

References
Carroll N 2015.
Reassignment of Montanazhdarcho minor as a nonazhdarchid member of the Azhdarchoidea. Journal of Vertebrate Paleontology abstracts.
Padian, K., Horner, J.R., and de Ricqlès, A.J 1993. A new azhdarchid pterosaur from the Two Medicine Formation (Late Cretaceous, Campanian) of Montana, identified on the basis of bone histology. Journal of Vertebrate Paleontology 13: 52A.
Padian K, de Ricqlès AJ and Horner JR 1995. Bone histology determines identification of a new fossil taxon of pterosaur (Reptilia: Archosauria)”, Comptes Rendus de l’Academie des Science Serie II (320): 77-84.
McGowen MR, Padian K, de Sosa MA and Harmon RJ 2002. Description ofMontanazhdarcho minor an azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. PaleoBios 22(1): 1–9.

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.

 

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.