A new cat-sized flightless azhdarchoid from Canada

Martin-Silverstone, Witton, Arbour and Currie 2019 bring us
news of a humerus and several vertebrae (some fused into a notarium) they taxonomically narrow down to a cat-sized Campanian (Late Cretaceous) azhdarchoid pterosaur. It was found on Hornsby Island, close to the much larger Victoria Island in Southwestern Canada.

The authors report,
“the individual was approaching maturity at time of death.”

In their discussion, the authors state:
“The thin bone walls, gracile bone construction and humeral morphology of RBCM.EH.2009.019.0001, indicate it clearly belonged to a volant Mesozoic animal, a pterosaur or avialan.”

There’s not much to see or reconstruct here.
The few bones found are fragments still in the matrix. The link below will take you to the online PDF.

On closer inspection,
the small triangular deltopectoral crest is smaller than in flightless pterosaurs (e.g. Sos2428 in Fig. 1) and the bone is thicker than one might expect of a volant pterosaur. The authors do not consider the possibility that their specimen had a volant ancestry, but was itself no longer volant, as happens often enough in the azhdarchid line of wading pterosaurs. Some were tiny (Fig. 1), some cat-sized, some man-sized and others much larger. Some were volant. Others were not, convergent with birds of all sizes.

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 1. The flightless pre-azhdarchid pterosaur, Sos 2428, along with two ancestral taxa, both fully volant. Note the reduction of the wing AND the expansion of the torso. This deltopectoral crest is at least twice the size of the new Canadian specimen

Dr. Witton has invested much time and treasure
in telling us giant azhdarchids were volant, despite the facts that weigh against that hypothesis. He also omits the data on three flightless pterosaurs, including Sos2428 (Fig. 1). Now we can add a fourth, his new cat-sized Hornby Island pterosaur.

Earlier co-author Witton
and Habib 2010 discussed hypothetical flightlessness in giant azhdarchids from many angles, but never introduced actual flightless taxa, two of which were known at the time. This online paper included infamous illustrations of an ornithocheirid manus in the process of a quadrupedal launch that had been cheated to implant the wing finger on the substrate, something that never happens according to the ichnite record. They did this by shrinking the free fingers.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 2. Quetzalcoatlus running like a bipedal lizard with no need or ability to fly.

Postscript
Interesting blog post here on an unfortunate bone misidentification on a paper earlier by one of the co-authors. Thank goodness Witton chose not to vilify his co-author.


References
Martin-Silverstone E, Witton MP, Arbour VM and Currie PJ 2019. A small azhdarchoid pterosaur from the latest Cretaceous, the age of flying giants. Royal Society open science 3: 160333. http://dx.doi.org/10.1098/rsos.160333
Witton MP, Habib MB 2010. On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. PLoS ONE 5(11): e13982. https://doi.org/10.1371/journal.pone.0013982

Time to trash the widely embraced ‘Azhdarchoidea’

According to Wikipedia
Unwin (2003) defined the group Azhdarchoidea as the most recent common ancestor of Quetzalcoatlus and Tapejara, and all descendants.

Unfortunately
Unwin’s phylogenetic analysis excluded several dozen relevant taxa. When those are added back in, as shown in the large pterosaur tree (LPT, 232 taxa), azhdarchids arise from certain phylogenetically miniaturized Dorygnathus clade specimens (TM 10341) while tapejarids arise from certain phylogenetically miniaturized germanodactylids (Nemicolopterus) and before that, phylogenetically miniaturized scaphognathids (Ornithocephalus brevirostris, BSPG 1971 I 17). Tapejarids and azhdarchids don’t have a common ancestor in the LPT until you go back to Sordes PIN 2585-25. And that was not the intent of Unwin 2003.

Competing hypotheses of relationships
by Naish and Martill 2006; Lu et al. 2008; Pinheiro et al. 2011; and Andres, Clark and Xu 2014 all suffer from the same cherry-picking and taxon exclusion issues. At least Vidovic and Martill 2014 added germanodactylids and dsungaripterids nesting basal to tapejarids, but failed to add dorygnathids and pre-azhdarchids among other relevant taxa basal to azhdarchids. By the way, you heard it here first: germanodactylids and dsungaripterids were ancestral to tapejarids. Thanks are due to Vidovic and Martill for confirming this.

Pterosaur workers are ‘missing the boat’
when they are content to cherry pick traditional genus-based taxa. If they were to employ more specimen-based taxa in an unbiased fashion, as the LPT does, they, too, would recover a wealth of interrelationships otherwise invisible to them.

The clade name Azhdarchia
is hereby defined as TM 10341, Beipiaopterus, their last common ancestor and all descendants. These include Huanhepterus, Ardeadactylus, CM 11426, BSPG 1911 I 31, the flightless azhdarchid JME-Sos 2428, JME Sos 2179, and the traditional azhdarchids, Jidapterus, Chaoyangopterus, Zhejiangopterus, Azhdarcho, Quetzalcoatlus and kin. With origins in the late middle Jurassic, and no matter what size, these are all stork-like waders, gradually getting phylogenetically larger, toothless and ultimately flightless as their distal wing phalanges become vestiges.

The Azhdarchidae.

Figure 1. The Azhdarchidae. Click to enlarge. (That’s a juvenile Zhejiangopterus shown). These are all waders.

We already have a suitable name for the clade Tapejaridae,
which developed elaborate head crests and never stopped flying (so far as is known), based on their elongate distal wing phalanges.

The new skull compared to other tapejarids. Click to enlarge.

Figure 2. Click to enlarge. The rising size of the tapejaridae. These are not waders.

The expansion of the antorbital fenestra above the level of the orbit
in tapejarids and azhdarchids is (I hate to be the only one saying the obvious) a convergent trait. LPT relationships were introduced and published in Peters 2007, and (with a few modifications to incomplete taxa) hold true today. Peters 2007 reported, Major clades typically have a spectral series of tiny pterosaurs at their base suggesting that paedomorphosis was a major factor in pterosaur evolution.” Since then, no other workers have included the vital and relevant tiny pterosaurs in their phylogenetic analyses.

It is also time to trash the clade ‘Pterodactyloidea’
When tiny pterosaurs are added to a phylogenetic analysis (click here) the traditional clade ‘Pterodactyloidea’ divides into two clades that arise from tiny Dorygnathus derived taxa (Fig. 1) and two more that arise from tiny Scaphognathus derived taxa (Fig. 3), for a total of four pterodactyloid-grade taxa. There’s one more semi-pterodactyloid clade,  Darwinopterus and kin, with a large skull and long neck, but also a long tail. And yet another, the anurognathids that do not have a large skull (exception: Dimorphodon) and long neck. However anurognathids do shrink the tail, a pterodactyloid-grade trait that Longrich, Martill and Andres 2018 used to nest anurognathids as the proximal outgroup to their clade ‘Pterodactyloidea’ with the mistakenly reconstructed Kryptodrakon (= Sericiterus) at the base. The LPT lumps and splits all pterosaurs in a logical and tenable fashion.

Figure 1. Scaphognathians to scale. Click to enlarge.

Figure 3. Scaphognathians to scale. Click to enlarge.

From one generation to another
If you were a full professor, would you venture to include taxa suggested by an amateur? So far, none have shown the courage to do so (see below), while outside of pterosaur studies, confirmation of discoveries first announced here has happened several times (e.g. Chilesaurus), without citation. So methods used here work.

Dr. S. Christopher Bennett once told me:
“If you submit that manuscript, it will not get published. And if you somehow get it published it will not get cited.” Uncanny how that prophecy came true… but it doesn’t reflect on the value of the manuscript.

And that’s why
this blog and the website ReptileEvolution.com were launched, outraged at the insanity and insular thinking out there.

PS. As I write this,
Bestwick, Unwin, Butler, Henderson and Purnell (2018) compiled statistics on pterosaur dietary preferences (over 300 pterosaur dietary statements identified from 126 published studies) employing a traditional cladogram with the tiny hand, four-toed crocodylomorph, Scleromochlus as the outgroup, anurognathids basal to eudimorphodontids, wukongopterids basal to ‘pterodactyloids’, cycnorhamphids nesting with ctenochasmatids, pteranodontids nesting with ornithocheirids, and tapejarids nesting with azhdarchids, with loss of resolution at half the nodes. It’s quite disheartening to see this, when we know better… through specimen-based taxon inclusion.

Pity the first author, poor PhD student (U of Leicester) Jordan Bestwick. He is under the tutelage of Dr. David Unwin. You might remember Leicester, was earlier seeking a pterosaur tracker, a student who could somehow find evidence for the invalidated pterosaur forelimb launch hypothesis. Evidently, this is how they operate: Don’t find out for yourself… rather your job is to continue the legacy and dictates of your professor(s).

In addition to the invalid Azhdarchoidea,
Dr. Unwin has promoted:

  1. the invalid ‘uropatagium‘ incorporating pedal digit 5 in basal pterosaurs
  2. the invalid deep chord wing membrane of pterosaurs
  3. the invalid quadrupedal basal pterosaur hypothesis
  4. the invalid pterosaur egg burial hypothesis
  5. the invalid quad-launch hypothesis of pterosaur takeoff
  6. the invalid archosauromorph (Scleromochlus) origin of pterosaurs (see above)
  7. the invalid modular evolution hypothesis to support
  8. the invalid nesting of the Darwinopterus clade basal to
  9. the invalid Pterodactyloidea.

Anyone can test these hypotheses by
adding taxa to current published studies using whatever characters one chooses. Really. That’s all it takes to upset these cherry-picked (taxon exclusion riddled) studies.

References
Andres B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology24: 1011–6.
Bestwick J, Unwin DM, Butler RJ, Henderson DM and Purnell MA 2018. Pterosaur dietary hypotheses: a review of idea and approaches. Biological Reviews online pdf
Longrich NR, Martill DM and Andres B 2018. Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biology, 16(3): e2001663.
Lü J, Unwin DM, Xu L and Zhang X 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften. 95 (9): 891–897.
Pinheiro FL et al. (4 co-authors) 2011. New information on Tupandactylus imperator, with comments on the relationships of Tapejaridae (Pterosauria). Acta Palaeontologica Polonica. 56 (3): 567–580.
Peters D 2007. The origin and radiation of the Pterosauria.Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. Pp. 139-190. in Buffetaut, E. & Mazin, J.-M., (eds.) (2003). Evolution and Palaeobiology of Pterosaurs. Geological Society of London, Special Publications 217, London, 1-347.

wiki/Azhdarchoidea
wiki/Pterodactyloidea

 

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. 

Restoring the skull of Quetzalcoatlus sp.

We know of at least three partial skulls of Quetzalcoatlus sp. (Kellner and Langston 1996), the smaller version of Q. northropi (Lawson 1975), for which no skull is known. This is how Kellner and Langston (1996) reconstructed the skull.

Figure 1. Quetzalcoatlus sp. skull according to Kellner and Langston (1996).

Figure 1. Quetzalcoatlus sp. skull according to Kellner and Langston (1996).

Since this is such a popular pterosaur, many have attempted restorations based on their access to the specimen and their own artistic license. See one here and another here.

Here’s how I do it.
Below are images traced from Kellner and Langston (1996), scaled to the same scale (they were nearly identical in length and proportion) then combined to create the restoration (Fig.1).

Figure 1. Quetzalcoatlus skulls individually and combined to create a restoration.

Figure 2. Quetzalcoatlus skulls individually and combined to create a restoration. Not preserved possible soft tissue in gray. Back of the skull based on chaoyangopterids and Zhejiangopterus. Not sure what to make of the two bony crest shapes (red and black), whether a result of taphonomy or individual variation. Considering the angle between the cranial and rostral parts of this skull, apparently Q kept its snout down, not out. 

The skull turns out to be a little taller due to a low rostral crest, with a taller antorbital fenestra. Kellner and Langson (1996) assumed that the dentary continued on to more of a point and that may be so considering the example of Azhdarcho. The details and sutures of the skull are sometimes easy to make out but otherwise the texture of the gnarled bone  makes things more difficult.

All the same size? Yes.
And what does that mean? Were all three specimens juveniles of the same age? Or adults of the same age but of a species distinct from Q. northropi? I don’t know.

Figure 3. The dentary tip of the TMM 42161 specimen, twisted and skewed in dorsal view. Not sure what to make of this. If  the tip does extend further (in pink), it likely does not extend very much further. The tip currently has the shape of a yardstick with some added ridges and valleys. Color represent distinct areas, not distinct bone. This is the anterior part of paired fused bones, the dentaries. Bottom view skewed segments unskewed. This dentary tip is wider than tall, unlike the tip of Eopteranodon and Eoazzhdarcho.

Figure 3. The dentary tip of the TMM 42161 specimen, twisted and skewed in dorsal view. Not sure what to make of this. If the tip does extend further (in pink), it likely does not extend very much further. The tip currently has the shape of a yardstick with some added ridges and valleys. Color represent distinct areas, not distinct bone. This is the anterior part of paired fused bones, the dentaries. Bottom view skewed segments unskewed. This dentary tip is wider than tall, unlike the tip of Eopteranodon and Eoazzhdarcho. Green areas are hypothetical lines to join and continue apparent missing areas. 

The dentary tip
I can only wonder what is going on at the tip of this dentary. It was skewed left and right several times, but in lateral view it appears undistorted. Distinct from sharp-jawed and tooth-tipped Eopteranodon and Eoazhdarcho (which are not azhdarchids), this rostral tip Fig. 3) is wider than tall, like a yardstick. It doesn’t appear strong enough to battle prey that fights back, but supports a gentle wading after tiny crustacean lifestyle.

References
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.

wiki/Quetzalcoatlus

The new Chaoyangopterus is really a Jidapterus. Close, but no cigar.

It really pays to make reconstructions. And to analyze traits in a large data matrix.

 Not Chaoyangopterus, but Jidapterus.

Figure 1. Not Chaoyangopterus, but Jidapterus is LPM-R00076.

In 2010, Zhou reported on a complete but disarticulated skeleton of a stork-like pterosaur, a small azhdarchid they assigned to Chaoyangopterus. They reported, “LPM-R00076 lacks a pneumatic foramen on the proximal end of first wing phalanx that has been reported in Jidapterus edentus (LÜ et al. 2006a). Therefore, LPM-R00076 is identified as Chaoyangopterus zhangi on the basis of the similar skull shape and limb proportions.

Chaoyangopterus  (Zhou 2012)

Figure 2. Click to enlarge. Left: Jidapterus. Right: Chaoyangopterus. Middle: Chaoyangopterus (Zhou 2012, LPM (Liaoning Paleontological Museum)-R00076) nests closer to Jidapterus, but it’s close. All of the data available has been crappy at best. They are all closely related.

Phylogenetic analysis in the large reptile tree nests the new specimen firmly with Jidapterus. Nested between them adds three steps. Nested with Chaoyangopterus adds 18 steps. Sure would be nice to get better resolution on those photos.

Eopteranodontids and early azhdarchids are very similar in appearance, but the large (derived from Germanodactylus) vs. small (derived from Dorygnathus) sternal complex is a dead giveaway, among several other traits. Closeups of the jawtips would be nice. Feet are good lumpers and dividers.  I’d like to correct any and all mistakes.

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
Zhou C-F 2010. New material of Chaoyangopterus (Pterosauria: Pterodactyloidea) from the Early Cretaceous Jiufotang Formation of western Liaoning, China. N. Jb. Geol. Paläont. Abh. 257/3, 341–350.

The Evolution of Gigantism in Pterosaurs: The Ancestry of Quetzalcoatlus

Earlier we followed up on a National Geographic article on how many generations it takes to create a blue whale and an elephant. Today we’ll look at the evolution of the giant pterosaur Quetzalcoatlus (Fig.1) from the Latest Cretaceous (65 mya) from a much smaller ancestor of the Late Jurassic (150 mya), a span of 85 million years.

Others consider azhdarchids, like Quetzalcoatlus, to be related to tapejarids based on the shared trait of an antorbital fenestra taller than the orbit. The large reptile tree did not recover that relationship, but found that antorbital trait to be a convergence.

The beauty of the large reptile tree and the large pterosaur tree is the ability to trace the ancestry of any listed taxon back to the basal tetrapod, Ichthyostega. Today we won’t go that far back. Rather we’ll start with the first Late Jurassic pterosaur in the lineage of Quetzalcoatlus that actually has the approximate proportions of Quetzalcoatlus. That pterosaur is tiny specimen inaccurately referred to Pterodactylus? elegans? BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog, Fig. 1).

Quetzalcoatlus and its ancestor, no 42, note scale bars.

Fig. 1. Quetzalcoatlus and its ancestor, no 42, note scale bars. Also note the flat rostrum in both taxa, distinct from the pointed tapejarid rostrum derived from Germanodactylus.

Similar but different, especially in size.
We’re often taught that as organisms grow larger they also become more robust, with stronger, thicker bones to withstand the effects of their greater mass and weight. Here, not so much. Giant Quetzalcoatlus was just as gracile as the VERY much smaller, no. 42. Sure the humerus is more robust. So is the pectoral girdle. Otherwise it’s hard to find thicker bones and the neck is definitely more gracile in Quetzalcoatlus. That’s engineering!!

Tiny no 42 is dwarfed by the specimen referred to Quetzalcoatlus, which is dwarfed by the hypothetical skull of Q. northropi, based on wing elements.

Figure 2. Tiny no 42 is dwarfed by the specimen referred to Quetzalcoatlus, which is dwarfed by the hypothetical skull of Q. northropi, based on wing elements. Click to learn more.

What can we learn here?
Between no. 42, which was reduced from early Dorygnathus specimens, and Quetzalocoatlus, one of the largest known azhdarchids, the proportions are not much different overall. This is likely due to the restrictions imposed by flight. Only certain balances between power and weight can fly. Over time and millions of generations the lineage of Quetzalcoatlus gradually grew and reengineered itself to withstand the increasing stresses imposed by that growth.

Forelimb Take-Off
Dr. Mike Habib (2008) has noted the greater size of the humerus vs femur in Quetzalcoatlus and other large pterosaurs. He didn’t mention no. 42, which does not have a humerus greater in diameter than the femur. Habib considered the more robust humerus a sign that pterosaurs used a vampire bat-like forelimb launch sequence demonstrated here, rather than a bird-like hind limb launch demonstrated here. Unfortunately, its all math at present. We know of no pterosaur take-off tracks, nor any that document the implantation of the wing metacarpal into the substrate. Rather only the fragile first three digits make any impression. Perhaps the increased size of the humerus is a sign that the pectoral engine for wing flapping is much larger to drive the larger wings. After all, traditional physics has to enter into pterosaur evolution someplace!

Tomorrow we’ll look at the similar situation in the ancestry of Arthurdactylus and Anhanguera, two giant ornithocheirids.

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
Habib MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana B28:159-166.
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
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.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Quetzalcoatlus

The Azhdarchoidea?

The Azhdarchoidea (Unwin 1995) is a putative clade of derived pterosaurs created to unite the Azhdarchidae (Quetzalcoatlus and kin) with the Tapejaridae (Tapejara and kin). Characters uniting taxa within this putative clade include: 1) Orbit positioned lower than dorsal rim of nasoantorbital fenestra; 2) Manual 4.2 more than a third shorter than m4.1.

Is Azhdarchoidea a Valid Clade?
The tall antorbital fenestra either unites Chaoyangopterus with Huaxiapterus (Fig. 1) or this trait developed by convergence. Manual 4.2 is indeed only 2/3 the length of m4.1 in Chaoyangopterus, but m4.2 is a bit too long (82%) in Huaxiapterus. Manual 4.2 is likewise less than 2/3 of m4.1 in the tiny pterosaur, n42. In Tapejara m4.2 is also a bit too long, but 2/3 the length of m4.1 in other tapejarids, such as Tupuxuara.

utative members of the Azhdarchoidea

Figure 1. Click to enlarge. Putative members of the Azhdarchoidea include Chaoyangopterus and Huaxiapterus (red arrows). The larger study found no clade uniting just the Azhdarchidae and the Tapejaridae. Instead n42 was found to be basal to azhdarchids and Germanodactylus cristatus n61 was found to be basal to tapejarids.

Similarities
It’s easy to see several similarities in azhdarchids and tapejarids, including the elongated metacarpus, the depth of the suborbital jugal, the depth of the mandible at mid length, and the short m4.4. Unfortunately many other distinctions separate these two taxa in the larger pterosaur tree.

Distinctions
In dorsal view, the azhdarchid mandible has parallel sides ending in a rounded tip. In tapejarids and germanodactylids the mandible is sharp with a tooth at its tip. A posterior cranial crest is present in tapejarids and germanodactylids, but not in azhdarchids. The antorbital fenestra extends for 2/3 of the rostrum in tapejarids and germanodactylids, not in azhdarchids. The number of dorsal vertebrae is smaller in azhdarchids and protoazhdarchids. The pedal phalangeal ratios are more similar in protoazhdarchids and azhdarchids than in tapejarids. Similar pedal phalangeal proportions unite germanodactylids and tapejarids.

Aurorazhdarcho

Figure 2. Left to right, Eopteranodon, Wellnhofer's No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

A Basal Azhdarchoid?
Aurorazhdarcho (Frey, Meyer and Tischlinger 2011, Fig. 2) was promoted as the basalmost azhdarchoid. Unfortunately no phylogenetic analysis was published. Here, in the large pterosaur tree, Aurorazhdarcho nested with other stork-like pterosaurs, Eopteranodon and Eoazhdarcho, at the base of Nyctosaurus + Pteranodon, distinct from both the Tapejaridae and the Azhdarchidae.

The Benefit of a Larger Family Tree
Here again the benefit of a larger family tree permits an entire suite of traits, from head to toe, define cladistic relations. More taxa is the key to understanding, as any paleontologist will tell you, except when dealing with pterosaur relations [sarcasm]. Not sure why other paleo scientists refuse to expand their taxon list to match mine.

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, Meyer CA and Tischlinger H 2011. The oldest azhdarchoid pterosaur from the Late Jurassic Solnhofen Limestone (Early Tithonian) of Southern Germany. Swiss Journal of Geosciences 104 (Supplement 1): 35–55. doi:10.1007/s00015-011-0073-1.
Unwin DM 1995. Preliminary results of a phylogenetic analysis of the Pterosauria (Diapsida: Archosauria); pp. 69-72 in Sun, A. and Wang, Q.-Y. (eds.), Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, short papers. China Ocean Press, Beijing.

wiki/Azhdarchoidea