Largest birds and pterosaurs to scale (finally!)

Question: Could the largest azhdarchids fly?
Tradition says: Yes! Most pterosaur workers say: Yes! Flying azhdarchid models say: Yes!

Heresy:
We looked at that question earlier and came to another conclusion based on comparable vestigial wingtip phalanges in flightless pterosaurs. Today there’s more to consider.

Let’s take another look at that same problem,
this time comparing the largest flying bird to the largest flying pterosaurs, and the largest non-flying bird to a giant pterosaur (Fig. 1). Since the largest flying birds and pterosaurs had the longest wing/neck and wing/torso ratios, the reduction of wing span/neck length points toward flightlessness—if analogous.

As reported yesterday,
lacking the ability to fly removes the constraints for multiple increases in size. We know of no pterosaurs that had vestigial wings, only vestigial distal wing phalanges. Three of the four flightless pterosaurs we looked at earlier were pterodactyloid-grade quadrupeds, so their free fingers had to contact the substrate. Moreover, all flightless pterosaurs could still flap vigorously, whether to ward off threats by display and/or increase thrust while fleeing.

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale. Are large soaring birds analogs to large flying pterosaurs. If so, then are large non-flying birds analogs to large non-flying pterosaurs. Does giving up flight enable giantism in birds and pterosaurs?

While recognizing obvious differences
between the largest pterosaurs and birds, which are more alike?

On the one hand
we have pterosaurs and birds with shorter necks, shorter legs and longer wings.

On the other hand
we have a pterosaur and a bird with a longer neck, longer legs and a relatively shorter wing (compared to those of volant pterosaurs). Is it really as simple as that?

Or did I cherry-pick taxa?

Figure 2. Azhdarchids are stork-like waders, so Ciconia, the stork, is a good analog. It is notably smaller than the smallest known Quetzalcoatlus.

Figure 2. Azhdarchids are stork-like waders, so Ciconia, the stork, is a good analog. It is notably smaller than the smallest known Quetzalcoatlus, about the size of flying azhdarchids.

Azhdarchids are often compared to storks.
And they do have similar proportions (Fig. 2). But all storks fly and some of the largest (e.g. Ciconia) are only half as tall as the smallest Quetzalcoatlus sp. We know of no giant storks. Even so, at half as tall, the legs of Ciconia were equal in length to the larger Q. sp, the torso was similar in size, and the neck and skull were only half as long. All this would appear to make azhdarchids top heavy relative to the volant stork (Fig. 3), despite a longer wing span, even with reduced distal elements.

Figure 3. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.

Figure 3. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct albatross/gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork and gannet, despite the longer wingspan compared to the stork. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of Pelagornis show what is typical for a giant volant wide-ranging tetrapod, and Q. sp. comes up short in comparison.

What about those wings?
Compared to the stork, Q sp. had longer wings. Compared to albatrosses and pterosaurs, Q. sp. had shorter wings. In any case, that long neck is strikingly different in azhdarchids. Such a long lever arm had to affect the center of balance (Fig 3 red line).

Figure 3. Quetzalcoatlus model ornithopter by Paul Macready getting walked to its take-off point.

Figure 4. Quetzalcoatlus model ornithopter by Paul Macready getting walked to its take-off point. The wing chord extends to the posterior pelvis, which is invalid. The demonstrated wing chord is shown in figure 3.

What about that mechanical flying Q. sp?
Paul Macready built and flew a gliding Q. sp., (Fig. 4) not a Q. northropi. It did not have a long enough neck or large enough skull. As it was, it was well-engineered and all the mechanics in the torso were unlikely duplicated in the Late Cretaceous taxon.

Figure 5. The Macready flying model compared to Q. sp. Perhaps it has always been overlooked that the neck proportions were changed and heavy mechanical motors and batteries filled the torso.

Figure 5. The Macready flying model compared to Q. sp. Perhaps it has always been overlooked that the neck proportions were changed and heavy mechanical motors and batteries filled the torso. The hind limbs are unnaturally tucked in in the model, following Kevin Padian’s invalidated view that pterosaurs were close to dinosaurs.

The question(s) comes down to:
If large soaring birds are analogs to large flying pterosaurs, then are the largest non-flying birds analogs to the largest pterosaurs? Does giving up flight enable and promote gigantism in birds AND pterosaurs?

At present, the evidence says: yes.

However, it’s not that giant pterosaurs were “too big to fly”.
Here’s the working hypothesis: Smaller pterosaurs that stopped flying were then able to grow much bigger, with less constraint for maintaining a center of balance at the shoulders.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure  6. Quetzalcoatlus running like a lizard prior to takeoff. Leaning forward while running fast is what humans do to. Perhaps the neck was held more erect, like an ostrich or giraffe, back in the Late Cretaceous.

Not sure why it took so long
to put large pterosaurs and birds together. This should have been posted years ago.

 

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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

 

Azhdarcho restored (from bits and pieces)

Earlier
we looked at the neck and skull of Azhdarcho… Today we’ll put all the bits and pieces we know (from several individuals, unfortunately) to see what we get, following the Q. sp. bauplan (Fig. 1).

Figure 1. Azhdarcho to scale with more complete smaller Quetzalcoatlus specimen and in proportion to the bauplan of Q. sp. Note the robust femur and gracile humerus. These together with the small sternal complex and short distal wing elements indicate a flightless condition.

Figure 1. Azhdarcho to scale with more complete smaller Quetzalcoatlus specimen and in proportion to the bauplan of Q. sp. Note the robust femur and gracile humerus. These together with the small sternal complex and short distal wing elements indicate a flightless condition.

Azhdarcho lancicollis (Nesov 1984, Averianov 2010) is the namesake for the clade Azhdarchidae. This species is known from several individuals of various sizes and very few complete bones. That is why reconstructions of this genus are rare. This reconstruction is based on the more complete Q. sp., but about half as tall.

Given these limitations,
(no complete long bones), the femur appears to be more robust than in other azhdarchids, while the humerus is more gracile. Only in Huanhepterus is the femur so relatively short. The sternal complex is quite small, but with a deep cristospine, distinct from other azhdarchids. (Perhaps the rest of the sternal complex is missing.) Manual 4.4 was identified by Averianov, but it appears to be the distal portion of m4.3. The scale bars for the distal femur appear to be in error, or apply to a much larger individual (see Fig. 1).

The invisible aid in this reconstruction
is the observation that in nearly all post-Huanhepterus azhdarchids, the metacarpus, manual digit 4 and tibia are similar in length (Fig. 1), no matter how small or tall… probably to facilitate terrestrial locomotion.

Unfortunately,
not enough is known of Azhdarcho to add it to the LRT. So much has to be imagined.

References
Averianov AO 2010. The osteology of Azhdarcho lancicollis Nessov, 1984 (Pterosauria, Azhdarchidae) from the Late Cretaceous of Uzbekistan. Proceedings of the Zoological Institute of the Russian Academy of Sciences, 314(3): 246-317.
Nesov LA 1984. Upper Cretaceous pterosaurs and birds from Central Asia. Archived 17 March 2012 at the Wayback Machine. Paleontologicheskii Zhurnal, 1984(1), 47-57.

wiki/Azhdarcho

Help fix ‘Dracula’ the giant Romanian pterosaur

This comes from a press release with photos,
not an academic paper. Evidently there is a new giant azhdarchid pterosaur named Dracula, known from ‘a majority of bones’, from which the following museum mount was created (Fig. 1).

Figure 1. Dracula the giant azhdarchid pterosaur museum mount. Hopefully it's not too late to fix the problems here.

Figure 1. Dracula the giant azhdarchid pterosaur museum mount. Hopefully it’s not too late to fix the problems here. Most will just take some twisting, some disassembly and reassembly.

Here are the visible problems:

  1. The ridged sternal complex looks like it was created from gastralia. No other sternal complex has such ridges and those from azhdarchids are not big and square.
  2. Fingers 1–3 are located laterally. They should be medially.
  3. The pteroid should anchor on the radiale (not the ulnare), the pre-axial carpal on the medial side of the distal carpal. And the pteroid should always point back to the deltopectoral crest.
  4. In azhdarchids m4.4 is always tiny,
  5. This looks like a dinosaur pterygoid.
  6. Pedal digit 5 should be on the lateral side of the foot.
  7. Twist metacarpal 4 90º laterally so the wing finger extends posterior to the forelimb.

Translated from German:
“In Denkendorf you can now marvel at a bone of “Dracula”, several dozen other bone fragments of the animal are located in Florida, where they are scientifically studied with elaborate technology. A publication on the sensation finding, the researchers have announced for the fall. Until then, “Dracula” remains only the unofficial name of the pterodactyl.”

Maybe it is all based on just the one cervical and some shards. We’ll find out later.

Some links below,
courtesy of Ben Creisler on the Dinosaur Mailing List.

http://www.donaukurier.de/nachrichten/panorama/Denkendorf-DKmobil-Dracula-in-Denkendorf;art154670,3721531

https://www.n-tv.de/wissen/Museum-stellt-Riesensaurier-Dracula-aus-article20350242.html

The origin of giant birds: Grus, the giant stilt

Basal taxa near this node are medium-sized birds
like Aramus the limpkin and Corvus the crow.

So
the stilt, Himantopus, and the sunbittern Eurypyga, both medium-sized birds, are basal to the crane, Grus (Fig. 1), and all are more closely related to each other than to other taxa in the large reptile tree (LRT, 1119 taxa).

Figure 1. Himantopus the stilt compared and to scale with the larger Grus, the crane.

Figure 1. Himantopus the stilt compared and to scale with the larger Grus, the crane.

Here again, in the larger descendant (Grus)

  1. the skull is smaller
  2. the neck is longer with more vertebrae,
  3. the torso is longer, larger
  4. the hind limbs are more robust

In this case, since both taxa are volant
and the size change is not as great as in other examples, the forelimbs are not reduced, the ribcage does not angle anteriorly, the sternum is not smaller, the pelvis is not longer posteriorly, the center of balance does not shift to below the pelvis. In this odd case, the sternum extends anteriorly, curving up toward the scapula.

Figure x. Bird giants in the bird subset of the LRT.

Figure 2. Bird giants in the bird subset of the LRT.

Himantopus mexicanus (Muller 1776) is the extant black-winged stilt. It is a wading bird with extraordinary long legs. Like the hummingbird, the beak is long and gracile. They eat buried invertebrates in mudflats near water.

Grus grus (Linneaus 1758; 120 cm long) is the extant common crane. The skull is much shorter than the cervical series. The sternum extends anteriorly along the coracoids. Note pedal digit 4 has only three phalanges.

Note:
These two waders are structurally similar to the long-legged more primitive flamingoes, seriemas and secretary birds, but stork and stilt ancestors had shorter-legged crows for ancestors. Thus their long legs were secondarily evolved relative to basal euornithes. 

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. This image replaces an earlier one in which a smaller specimen of Zhejiangopterus was used.

Storks are similar to azhdarchid pterosaurs
Basal and outgroup taxa (Fig. 3), like no. 44 and no. 42 were small to tiny, able to wade in only the shallowest of water. Later taxa, like Huanhepterus, Sos 2428 and Jidapterus were larger, able to wade in deeper ponds. More derived azhdarchids, like Zhenjiangopterus and Quetzalcoatlus, could wade in (for humans) waist deep waters. And let’s not forget the hatchlings, which had to wade in shallower waters in every case.

References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Müller OF 1776. Zoologiae Danicae prodromus: seu Animalium Daniae et Norvegiae indigenarum characteres, nomina, et synonyma imprimis popularium. Hafniae, Typiis Hallageriis. 1-274.

wiki/Black-necked_stilt
wiki/Common_crane

A new look at Jidapterus (basal azhdarchid pterosaur)

Wu, Zhou and Andres 2017
bring us long anticipated details on Jidapterus (Early Cretaceous, Dong, Sun and Wu 2003) which was previously presented as a small in situ photograph lacking details. Even so a reconstruction could be made (Fig. 1). Coeval larger tracks (Elgin and Frey 2011) have been matched to that reconstruction.

Figure 2. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton.

Figure 1. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton.

Of interest today
is the fact that Jidapterus was originally and, so far, universally considered toothless. Its specific name, J. edentatus, refers to that condition. Wu, Zhou and Andres 2017 produced tracings (Figs. 2, 3) of the rostrum that are also toothless. However, they are crude and appear to miss the premaxilla and maxilla sutures, the palatal elements… and maybe some teeth. Those jaw rims are not slippery smooth like those of Pteranodon. Outgroups in the large pterosaur tree (LPT), all have tiny teeth.

Figure 2. Rostrum of Jidapterus (RCPS-030366CY) and traced according to Wu et al. and colorized using DGS to reveal skull sutures and possible teeth.

Figure 2. Rostrum of Jidapterus (RCPS-030366CY) and traced according to Wu et al. and colorized using DGS to reveal skull sutures and possible teeth. See figure 3 for details. What Wu, Zhou and Andres label the  “low ridge of rostrum” is here identified as the rostral margin above the palatal portion. 

The cladogram of Wu, Zhou and Andres
lacks dozens of key taxa found in the LPT that separate azhdarchids from convergent tapejarids and shenzhoupterids. In the LPT giant azhdarchids arise from tiny toothy azhdarchids once considered Pterodactylus specimens… and these, in turn are derived from tiny and mid-sized dorygnathids in the Middle Jurassic.

What Wu, Zhou and Andres label the  “low ridge of rostrum”
is here identified as the rostral margin rim at the edge of the palate.

Figure 3. Focus on the rostral tip of Jidapterus shown in figure 2. Are these teeth?

Figure 3. Focus on the rostral tip of Jidapterus shown in figure 2. Are these teeth? You decide. I present the data. 

As in all pterosaurs
each premaxilla of Jidapterus has four teeth according to this data.

Are these tiny teeth?
Or are they tiny occlusions and/or chisel marks. Let’s get even better closeups to figure this out. Phylogenetic bracketing indicates either tiny teeth or edentulous jaws could be present here.

References
Dong Z, Sun Y and Wu S 2003. On a new pterosaur from the Lower Cretaceous of Chaoyang Basin, Western Liaoning, China. Global Geology 22(1): 1-7.
Elgin and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1
Wu W-H, Zhou C-F and Andres B 2017. The toothless pterosaur Jidapterus edentus (Pterodactyloidea: Azhdarchoidea) from the Early Cretaceous Jehol Biota and its paleoecological implications. PLoS ONE 12(9): e0185486.

wiki/Jidapterus

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.