150 million years of pterosaur flight efficiency

Venditti et al. 2020
attempts to chronicle an increase in pterosaur flight efficiency over their 150 million year long clade span.

From the Venditti et al. abstract:
“The long-term accumulation of biodiversity has been punctuated by remarkable evolutionary transitions that allowed organisms to exploit new ecological opportunities. Mesozoic flying reptiles (the pterosaurs), which dominated the skies for more than 150 million years, were the product of one such transition. The ancestors of pterosaurs were small and probably bipedal early archosaurs (Andres et al. 2014), which were certainly well-adapted to terrestrial locomotion.”

Citation and taxon exclusion here. Andres et al. 2014 cherry-picked four euarchosauriform outgroups for the Pterosauria: Euparkeria, Ornithosuchus, Herrerasaurus and Scleromochlus. All of these taxa have a short to vestigial manual digit 4, the opposite of pterosaurs. This list followed the direction of co-author Mike Benton, well known for citation and taxon exclusion to promote his pet hypotheses, invalidated by Peters 2000, 2007, 2009. Readers have seen Benton omissions many times. The actual ancestors of pterosaurs were not archosaurs, but these lepidosaurs: Cosesaurus (Fig. 1), Sharovipteryx and Longisquama. So Venditti et al. 2020 starts off poorly, without a proper phylogenetic context.

By the way, Andres et al.  2014 did not find ‘the earliest pterodactyloid,’ but bits and pieces of a gracile dorygnathid, Sericipterus found in the same formation.

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 1. Click to enlarge and animate. Cosesaurus flapping – fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Continuing from the Venditti et al. abstract:
“Pterosaurs diverged from dinosaur ancestors in the Early Triassic epoch (around 245 million years ago); however, the first fossils of pterosaurs are dated to 25 million years later, in the Late Triassic epoch.”

False: Pterosaurs diverged from fenestrasaur ancestors (Peters 2000).

“Therefore, in the absence of proto-pterosaur fossils, it is difficult to study how flight first evolved in this group.”

False. We have those proto-pterosaur fossils and pterosaur ancestors all the way back to Cambrian chordates. Adding taxa resolved this problem in Peters 2000, 2007, 2009 and that continues today.

“Here we describe the evolutionary dynamics of the adaptation of pterosaurs to a new method of locomotion. The earliest known pterosaurs took flight and subsequently appear to have become capable and efficient flyers. However, it seems clear that transitioning between forms of locomotion2,3—from terrestrial to volant—challenged early pterosaurs by imposing a high energetic burden, thus requiring flight to provide some offsetting fitness benefits.”

Or the other way around, as documented by the four fenestrasaurs listed above.

“Using phylogenetic statistical methods and biophysical models combined with information from the fossil record, we detect an evolutionary signal of natural selection that acted to increase flight efficiency over millions of years.”

What is ‘flight efficiency’? Are hummingbirds more efficient? Or are albatrosses? Or ducks? Did the authors use the proper pterosaur wing shape (Fig. 2) ? Or the traditional invalid batwing-shape preferred by those in the Benton arc.

The Vienna Pterodactylus.

Figure 2. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. There is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

“Our results show that there was still considerable room for improvement in terms of efficiency after the appearance of flight.”

Without valid outgroups, how do they know? They don’t.

“However, in the Azhdarchoidea4, a clade that exhibits gigantism, we test the hypothesis that there was a decreased reliance on flight5,6,7 and find evidence for reduced selection on flight efficiency in this clade.”

Odd that these authors do not include the many examples of flightless pterosaurs, including derived and sometimes giant members of the Azhdarchidae.  They only say ‘there was a decreased reliance on flight.’

“Our approach offers a blueprint to objectively study functional and energetic changes through geological time at a more nuanced level than has previously been possible.”

There is no ‘blueprint’ here, only more misdirection and mythology. Sad that the works of professor Mike Benton have now become suspect following the present continuation of his long-standing pattern of cherry-picking and taxon exclusion favoring the textbooks and lectures that provide his income.


References
Andres B, Clark J and Xu, X 2014. The earliest pterodactyloid and the origin of the group. Current Biology 24:1011–1016 (2014).
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Hist Bio 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Venditti C, Baker J, Benton MJ, Meade A and Humphries S 2020. 150 million years of sustained increase in pterosaur flight efficiency. Nature https://doi.org/10.1038/s41586-020-2858-8

From the Nature comments section:
“The ancestors of pterosaurs were recovered twenty years ago (in Peters 2000) by simply adding Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama to four previously published analyses. Peters (2007) nested these bipedal taxa within the Lepidosauria by once again simply adding taxa. Omitting citations and omitting taxa results in statements like the following found in the Venditti et al. 2020 abstract: “in the absence of proto-pterosaur fossils, it is difficult to study how flight first evolved in this group.” Had the authors included Cosesaurus they would have known this taxon was flapping without flying due to a locked down, stem-shaped coracoid otherwise found only in birds and pterosaurs. Bats flap anchored by an analogous clavicle.”

 

New Quetzalcoatlus northropi skeletal model from Triebold Paleontology

Short one today
… focusing on a tall pterosaur skeleton model.

Figure 1. A Quetzalcoatlus northropi model from Triebold Paleontology scaled up from a Q. sp. sculpture I made and sold to Triebold.

Figure 1. A Quetzalcoatlus northropi model from Triebold Paleontology scaled up from a Q. sp. sculpture I made and sold to Triebold. Maybe it is posed trying to cool itself off, by those wing fingers can fold up against the arms for membrane protection.

First time I’ve seen this. 
Although I heard rumors that Mike Triebold (Triebold Paleontology) had scaled up the Q. sp. model I sold him a few years ago (Fig. 2) to create a 3x taller Quetzalcoatlus northropi model (Fig. 1). Giants are fascinating.

Quetzalcoatlus neck poses. Dipping, watching and displaying.

Figure 2. Quetzalcoatlus neck poses. Dipping, watching and displaying. Yes, that was my living room.

The shorter original was held together by wire
so it could be manipulated into one pose after another, or stuffed away into a small box.

As a reminder,
the brevity of the wings (vestigial distal phalanges) and the top-heavy proportions otherwise mark this as a flightless pterosaur.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 3. Quetzalcoatlus running like a lizard unable to take off due to vestigial distal wing elements and proportions that sent the center of balance anterior to the wing chord.

Even so, those wings were powerful thrusters
for speedy getaways on land (Fig. 3). I realize this is heresy, but facts are facts. Clipped wings in birds and pterosaurs means they cannot fly. And only flightless birds and pterosaurs are able to achieve such giant sizes (Fig. 4).

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.

Quetzalcoatlus wingspan compared to other azhdarchids

There are those who think
the giant azhdarchid pterosaur, Quetzalcoatlus (Fig. 1), was flightless. Almost all others think Quetzalcoatlus was the largest flying animal of all time. The question is: were the wings of Quetzalcoatlus large enough to initiate and sustain flight?

Sometimes it just helps to compare
azhdarchids to azhdarchids to azhdarchids. In this case we’ll compare Quetzalcoatlus in dorsal view to two azhdarchids so small that traditional paleontologists don’t even consider them to be azhdarchids. BSPG 1911 I 31, (Figs. 2, 3) is a traditional, small volant pterosaur with a long neck and a standard pterosaur wingspan. JME-Sos 2428 (Fig. 2) is an odd sort of flightless pterosaur with a very much reduced wingspan. Neither of these taxa seems to ever make it to the cladograms of other workers.

Figure 1. Quetzalcoatlus in dorsal view compared to two much smaller azhdarchids from the Solnhofen formation, JME-Sos 2428, a flightless pterosaur, and BDPG 1911 I 31, a volant pterosaur. The wingspan of Quetzalcoatlus does not match that of the much smaller azhdarchid, so perhaps the giant was unable to fly. At least, this is the evidence for flightlessness.

Figure 1. Quetzalcoatlus in dorsal view compared to two much smaller azhdarchids from the Solnhofen formation, JME-Sos 2428, a flightless pterosaur, and BDPG 1911 I 31, a volant pterosaur. The wingspan of Quetzalcoatlus does not match that of the much smaller azhdarchid, so perhaps the giant was unable to fly. At least, this is the evidence for flightlessness.

When you compare azhdarchids to azhdarchids to azhdarchids
you get the overwhelming impression that IF Quetzalcoatlus was volant, it would not have reduced the distal wing phalanges so much. And yet it did, just like other flightless pterosaurs did. Since weight increases by the cube as size in dorsal view increases by the square, the wings of the giant should actually be larger than those of the smaller azhdarchid to handle the relatively larger mass.

So what did Quetzalcoatlus use its flightless wings for?
Thrust (Fig. 2).

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 2. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

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

Fig. 3. Quetzalcoatlus and its ancestor, BSPG 1911 I 31, note scale bars. At 72dpi, the pterosaur on the left is nearly full scale on a monitor. The one on the right is as tall as a tall human, with giant relatives more than doubling that height. 

Contra tradition, the azhdarchid bauplan
was initiated with Late Jurassic small pterosaurs like BSPG 1911 I 31, so misbegotten  that traditional paleontologists have forgotten to give it its own generic and specific name distinct from the wastebasket taxon Pterodactylus, with which it is not related, as we learned earlier here.


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.
Witton MP and Habib MB 2010. On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PloS one, 5(11), e13982.

More data here: why-we-think-giant-pterosaurs-could-fly-not/

wiki/Quetzalcoatlus

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

Avimaia and her enormous egg

Bailleul et al. 2019 reported
on the posterior half of an Early Cretaceous enantiornithine bird from China, Avimaia schweitzerae (IVPP V25371, Figs. 1,2), including an enormous eggshell within her torso. The authors commented on the eggshell, which had not one, but several several layers, an abnormal condition, probably leading to the demise of the mother.

Phylogenetic analysis
The Bailleul et al. 2019 phylogenetic analysis nested Avimaia with eight most closely related taxa, of which only one, Cathayornis (Fig. 1), was also tested in the large reptile tree (LRT, 1425 taxa, subset Fig. 3) and likewise nested with Avimaia. Significantly, Cathayornis also has a very deep ventral pelvis capable of developing and expelling very large eggs.

Figure 1. Avimaia compared to Cathayornis to scale.

Figure 1. Avimaia compared to Cathayornis to scale. Cathayornis is the only other tested enantiornithine bird to have such a deep ventral pelvis.

A long, thin, straight, displaced bone was found
beneath the rib cage and identified as a rib by Bailleul et al. 2019. I wonder if it is instead a radius (Fig. 1) because it is not curved like a rib and it does not have an expanded medial process. The radius is vestigial. Regardless of the identify of this slender bone, Avimaia, appears to be ill-suited for flying based on her robust tibiae, short dorsal ribs  and giant egg. Cathayornis (Fig. 1) appears to be better-suited for flying, based on its chicken-like proportions.

Figure 2. Avimaia in situ. Some bones were originally mislabeled. Here the egg is reconstructed with a more traditional egg shape.

Figure 2. Avimaia in situ. Some bones were originally mislabeled. Here the egg is reconstructed with a more traditional egg shape.

Mislabeled bones
The right ‘pubis’ (Fig. 2) is the right ischium. The reidentified pubis has a pubic boot and the ischium does, not as in sister taxa. The authors failed to identify vestigial pedal digit 5.

The egg was originally reconstructed as a sphere (drawn as a circle) inside the abdomen. Here (Figs. 1, 2) the egg is reconstructed in a more traditional egg shape more likely to pass through the ischia and cloaca.

Figure 2. Subset of the LRT focusing on the clade Enantiornithes and the nesting of Avimaia as a derived taxon within that clade.

Figure 3. Subset of the LRT focusing on the clade Enantiornithes and the nesting of Avimaia as a derived taxon within that clade.

Most birds
lay more than one egg in a clutch. Another exceptional bird that develops a very large egg is the flightless kiwi (Apterypterx, Fig. 4).

Figure 2. Jurapteryx, Pseudocrypturus, Apteryx and Proapteryx to scale.

Figure 2. Jurapteryx, Pseudocrypturus, Apteryx and Proapteryx to scale.


References
Bailleul AM, et al. 2019. An Early Cretaceous enantiornithine (Aves) preserving an unlaid egg and probable medullary bone. Nature Communications. 10 (1275). doi:10.1038/s41467-019-09259-x
Pickrell, J 2019. “Unlaid egg discovered in ancient bird fossil”. Science. doi:10.1126/science.aax3954

wiki/Avimaia

Tiny flightless Early Cretaceous bird from Spain

Kaye et al. 2019
illuminated feathers with laser-stimulated fluorescence (Fig. 1) in a tiny, unnamed, enantiornithine bird specimen, MPCM-LH-26189 from the Las Hoyas locality (Barreminian, Early Cretaceous) of Spain. Based on the presence of those illuminated feathers and the size of the specimen (Fig. 2) the authors judged it to be a precocial hatchling, capable of walking shortly after hatching. This is the same specimen first described and not named by Knoll et al. 2018.

Figure 1. Specimen MPCM-LH-26189 a tiny enantiornithine bird in situ under white light (above, plate and counter plate) and under laser stimulated fluorescene (below). DGS colors added and used in the reconstruction in figure 2. Not sure what those red highlighted items are at lower right. See figure 2b for skull details. 

Figure 1. Specimen MPCM-LH-26189 a tiny enantiornithine bird in situ under white light (above, plate and counter plate) and under laser stimulated fluorescene (below). DGS colors added and used in the reconstruction in figure 2. Not sure what those red highlighted items are at lower right. See figure 2b for skull details.

A reconstruction of the new extra-tiny bird
is shown (Fig. 2) alongside that of another tiny coeval and closely related enantiornithine bird, Iberomesornis, to scale. Note the tiny fingers in the tiny MPCM specimen indicating flightlessness. The lower crus, distal tail and feet extend off the matrix block, so they remain unknown. Contra Kaye et al. 2019, the tiny MPCM specimen does not appear to have juvenile proportions, despite its reduced size.

Figure 2. Tiny Iberomesornis compared to scale with even tinier MPCM specimen. Note the tiny fingers. Two tibial lengths are presented since this data remains unknown. The tiny MPCM specimen does not appear to have juvenile proportions.

Figure 2. Tiny Iberomesornis compared to scale with even tinier MPCM specimen. Note the tiny fingers. Two tibial lengths are presented since this data remains unknown. The tiny MPCM specimen does not appear to have juvenile proportions.

Figure 2b. Skull of MPCM specimen traced using DGS methods and reconstructed using the resulting color parts.

Figure 2b. Skull of MPCM specimen traced using DGS methods and reconstructed using the resulting color parts.

It is always a good idea
to create a reconstruction (Fig. 2) from ‘road-kill’ taxa (Fig. 1). Such a reconstruction would have indicated the MPCM specimen did not have juvenile proportions, despite its small size… and it did not have traditional bird wings.

It is also a good idea to compare taxa
in a phylogenetic analysis to see how what you have relates to others of its kind. Here in the large reptile tree (LRT, 1423 taxa) the MPCM specimen nests close to Iberomesornis within the clade Enantiornithes.

Reversals
The MPCM specimen is the first enantiornithine to have short un-birdlike fingers (a reversal due to neotony) and such short forelimbs (another reversal).

If the tail lacked a pygostyle, as it currently appears, that would also be a reversal shared with long-tailed descendants, Pengornis and Protopteryx.

The small size of this possible adult specimen is also due to the same forces that led to tiny Iberomesornis in Early Cretaceous Spain. If the MPCM specimen had nested with much larger specimens, rather than tiny Protopteryx and Iberomesornis, then the MPCM specimen would more likely have been considered a juvenile.

Knoll et al. 2018 first studied the MPCM specimen
or its osteological correlates with other juvenile birds, not considering the possibility that phylogenetic miniaturization might make a tiny adult bird appear to be a juvenile. Perhaps that is why they concluded, “the hatchlings of these phylogenetically basal birds varied greatly in size and tempo of skeletal maturation.” Knoll et al. did not create a reconstruction nor put this specimen under phylogenetic analysis, probably on the basis of its presumed juvenile character. As your mother told you, if you assume something, you might miss out on its most intriguing aspects.

Phylogenetic analysis is so important
because it reveals so much more than just ‘eyeballing’ specimens.

Earlier we looked at other birds
that experienced a similar reversal from wings to hands. Among these are Mei long, Jinianhualong and Liaoningvenator.

In the Late Jurassic
tiny pterosaurs experienced a similar size squeeze. Traditionally considered juveniles, tiny hummingbird-sized taxa like B St 1967 I 276 (Fig. 3) and BMNH 42736 with fly-sized hatchlings, were among the few pterosaur lineages to survive the Jurassic and produce Cretaceous taxa.

From NatGeo.com
Paleo bird expert, Jingmai O’Connor reports, “All enantiornithines were super-precocial, born fully-fledged and ready to fly.”

A closer examination
indicates the MPCM specimen was never going to be ‘ready to fly.’ 

Figure 2. Smallest known bird, Bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults.

Figure 3. Smallest known bird, the bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults.

Is the MPCM specimen the smallest dinosaur?
If it is an adult, the MPCM specimen appears to be slightly larger than the smallest known dinosaur, the bee hummingbird (Fig. 3).

Since no one else wants to name the MPCM specimen,
probably because others considered this a hatchling rather than a phylogenetically miniaturized adult, let’s call him Microcursor sanspedes (‘tiny runner without feet”) in the meantime.


References
Kaye TG, Pittman M, Marugán-Lobón J, Martín-Abad H, Sanz JL and Buscalioni AD 2019. Fully fledged enantiornithine hatchling revealed by Laser-Stimulated Fluorescence supports precocial nesting behavior. Nature.com/scientific reports (2019) 9:5006 https://doi.org/10.1038/s41598-019-41423-7

Knoll, F. et al. (16 co-authors) 2018. A diminutive perinate European Enantiornithes reveals an asynchronous ossification pattern in early birds. Nature Communications 9, 937 (2018).

Publicity

https://www.nationalgeographic.com/science/2019/03/dinosaur-era-birds-born-ready-to-run-fossil-feathers-show/

When Pteranodon gets big, so do its wing bones, so it can keep flying

Earlier we looked at 
how the best known two dozen Pteranodon specimens can be readily split into about two dozen species. No two are alike and all can be lumped and split in a pterosaur cladogram. Contra traditional studies, no gender differences are apparent.

Size
As certain Pteranodon specimens grew larger and larger (Fig. 1) the arm bones, especially the antebrachium and metacarpal 4, became increasingly robust. This must have been a structural modification for keeping the largest specimens flying. Perhaps this is so because the weight increases more or less by the cube of the length… and the skulls + crests are getting larger, too.

Figure 1. Four Pteranodon specimens of increasing size. More robust arm bones are found in larger specimens. There is no reduction of distal wing elements.

Figure 1. Four Pteranodon specimens of increasing size. More robust arm bones are found in larger specimens. There is no reduction of distal wing elements in this volant genus.

Importantly,
the distal wing phalanges do not become vestiges in volant pterosaurs (Fig. 1) whether in the genus Pteranodon or the very large ornithocheirids.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 2. Quetzalcoatlus specimens to scale with a former 6-foot-tall president. Note the slender antebrachium (radius + ulna) and vestigial distal wing phalanges.

This is distinct from
mid-sized to giant azhdarchids, which have vestigial distal wing phalanges (Fig. 2). This pattern of wing reduction follows the same pattern seen in much smaller flightless pre-azhdarchid like Jme-Sos 2428, the flightless anurognathid PIN 2585/4 and flightless nyctosaurs, like Alcione.

There is a clade of pterosaur paleontologists and artists
who are enamored with the idea of giant flying azhdarchids. They say the math is on their side, but they’re not looking at what small pterosaurs do when they become flightless (see above). Given the present data, the flightlessness of six-foot-tall azhdarchids enabled the next magnitude in size increase, just as the near flightlessness of larger tinamous, secretary birds and parrots enabled the next magnitude of size increase to create giant flightless ostriches, terror birds and Gastornis.

FIgure 2. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus

FIgure 2. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus

The largest flying birds,
like Pelagornis, have proportions similar to those seen in the largest flying ornithocheirids and pteranodontids. The largest flying azhdarchid-like, long-legged wading birds, the storks, cranes and shoebills, never get much taller than a human. All larger birds are flightless. All larger azhdarchids are also flightless, based on their reduced wingtips and narrow ante brachia, but still use their wings for thrust (Fig. 3).

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 10. Quetzalcoatlus running like a lizard prior to takeoff. There was no longer any need for aerodynamic balance as a flightless sprinter, so the  neck were free to achieve giraffe-like proportions and size with a giant skull tipping the balance even further.


References

Juvenile Rhamphorhynchus and flightless pterosaur abstracts

Part 4
The following manuscripts are independently published online without peer-review at the DavidPetersStudio.com website. http://www.davidpetersstudio.com/papers.htm

Better to put them out there this way
than to let these works remain suppressed. Hope this helps clarify issues.


Peters D 2018g. First flightless pterosaur
PDF of manuscript and figures

Pterosaur fossils have been discovered all over the world, but so far no flightless pterosaurs have been reported. Here an old and rarely studied pterosaur fossil (Sos 2428) in the collection of the Jura Museum in Eichstätt, Germany, was re-examined and found to have a reduced pectoral girdle, small proximal wing elements (humerus, radius and ulna), three vestigial distal wing elements, the relatively longest pelvis of any pterosaur and the widest gastralia, or belly ribs. This discovery represents a unique morphology for pterosaurs. The Jura specimen lacked the wing size, forelimb muscularity and aerodynamic balance necessary to sustain flapping flight. It was a likely herbivore.


Peters D 2018h. First juvenile Rhamphorhynchus recovered by phylogenetic analysis
PDF of manuscript and figures
Standing seven to 44 centimeters in height, a growing list of 120+ specimens assigned to the pterosaur genus Rhamphorhynchus are known chiefly from the Solnhofen Limestone (Late Jurassic, southern Germany). An early study recognized five species and only one juvenile. A later study recognized only one species and more than 100 immature specimens. Phylogenetic analyses were not employed in either study. Workers have avoided adding small Solnhofen pterosaurs to phylogenetic analyses concerned that these morphologically distinct specimens were juveniles that would confound results. Here a large phylogenetic analysis that includes tiny Solnhofen pterosaurs tests that concern and seeks an understanding of relationships and ontogeny within the Pterosauria with a focus on Rhamphorhynchus. 195 pterosaurs were compiled with 185 traits in phylogenetic analysis. Campylognathoides + Nesodactylus were recovered as the proximal outgroups to the 25 Rhamphorhynchus specimens. The ten smallest of these nested at the clade base demonstrating phylogenetic miniaturization. Two Rhamphorhynchus had identical phylogenetic scores, the mid-sized NHMW 1998z0077/0001, and the much larger, BMNH 37002. These scores document a juvenile/adult relationship and demonstrate isometry during pterosaur ontogeny, as in the azhdarchid, Zhejiangopterus, and other pterosaurs. Rather than confounding results, tiny Solnhofen pterosaurs illuminate relationships. All descended from larger long-tailed forms and nested as transitional taxa at the bases of the four clades that produced all of the larger Late Jurassic and Cretaceous pterodactyloids. No long-tailed pterosaurs survived into the Cretaceous, so miniaturization was the key to pterosaur survival beyond the Jurassic.

These manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1256 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.

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

New flightless and giant nyctosaurs: Alcione and Barbaridactylus

Scale bar problems
and a lack of reconstructions in the original paper are issues here.

Longrich, Martill and Andres 2018
bring us news of “a diverse pterosaur assemblage from the late Maastrichtian of Morocco that includes not only Azhdarchidae but the youngest known Pteranodontidae and Nyctosauridae. [This] dramatically increases the diversity of Maastrichtian pterosaurs. At least 3 families —Pteranodontidae, Nyctosauridae, and Azhdarchidae — persisted into the late Maastrichtian. These patterns suggest an abrupt mass extinction of pterosaurs at the K-Pg boundary.”

The authors summary starts off with an invalid statement:
“Pterosaurs were winged cousins of the dinosaurs.”  That was invalidated by Peters 2000, 2007 and ignored every since. We looked at that problem earlier here, here and here in a 3-part series testing all candidates. It’s time to realize that no one will ever find pterosaur kin among the dinos. They’ve already been clearly identified among the lepidosaurs.

The authors failed to include the Maastrictian tupuxuarid
found in southern Texas (Fig. 1; TMM 42489-2) and did not consider the Maastrichtian footprints discovered in 1954 and reexamined in 2018 that include two ctenochasmatids we will look at tomorrow.

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.

Alcione elainus gen. et sp. nov.
The new 1.5x larger nyctosaurid, Alcione elainus, known from disassociated bones including a shorter radius + ulna, a shorter metacarpal 4, a larger femur, and a tiny sternal complex (identified as a ‘sternum’ in the text) only 40 percent the size of a standard nyctosaur sternal complex (if the scale bars are correct). When placed on a reconstruction of a more complete Nyctosaurus (UNSM 93000; Fig. 2), scaled to the humerus, the result produces a likely flightless nyctosaur. Strangely, the authors called this a “small nyctosaur” even though it is half again larger than UNSM 93000. The authors mislabeled the shorter, straighter scapula as a coracoid, and vice versa.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved.

Figure 2. GIF movie of Nyctosaurus and Alcione showing a likely flightless nyctosaur based on the parts preserved. Three frames change every 5 seconds. The sternum is tiny (assuming the scale bars are correct), the metacarpus and antebrachium are short and the femur is long.

They did not mention the possibility of flightlessness.
They did report, “The abbreviated distal wing elements in Alcione indicate a specialized flight style. The short, robust proportions suggest reduced wingspan and increased wing loading, implying distinct flight mechanics and an ecological shift. Short wings would increase lift-induced drag at low speeds, but reduced wing areas would decrease parasite drag at high speeds, suggesting that Alcione may have been adapted for relatively fast flapping flight compared to other nyctosaurids. Alternatively, reductions in wingspan might represent an adaptation to underwater feeding, i.e., plunge diving of the sort practiced by gannets, tropicbirds, and kingfishers, where smaller wings would reduce drag underwater.”

Not sure why they mentioned
‘distal wing elements’ here. They did not list or discuss distal wing elements elsewhere. Perhaps they meant proximal.

The reconstructed mandible of Alcione
is narrower than the rostrum in UNSM 93000.

Based on the vestigial fingers of UNSM 93000
and the short metacarpus of the new specimen, Alcione might have been the first pterosaur to walk on metacarpal 4, albeit at the very end of the reign of pterosaurs.

Other flightless pterosaurs include:
the basal azhdarchid form the Solnhofen, Jme-Sos 2428 and the Late Jurassic anurognathid PIN 2585/4 from the Sordes slab. They demonstrate that the distal wing elements reduce first. Thus the reconstruction, based on nyctosaur patterns restores a wing that was not volant.

Longrich, Martill and Andres did find a giant nyctosaur
which they named Barbaridactylus grandis based on a large humerus (Fig. 3). The humerus of the more complete UNSM 93000 specimen is 9.5 cm. By comparison the humerus in Barbaridactylus is 22.5 cm. I’m going to trust the text comment that the ulna + radius are 1.3x longer than the humerus. The scale bars indicate about half that length. Similar problem possible in the scapula/coracoid, according to the nyctosaur bauplan.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown.

Figure 3. Barbaridactylus, a giant nyctosaurid. If the wing was like UNSM 93000, then it could fly. If the wing was like Alcione, then it could not. The scale bars did not match the text description on the ulna + radius, so both sizes are shown. Sometimes you have to be prepared for the occasional mistake in a published paper.

Other giant nyctosaurs
Earlier and here we noted giant nyctosaurs were flying over the Niobrara Sea (midwest North America) based on a large wing finger with unfused extensor tendon process (YPM 2501) and a large nyctosaur pelvis (KUVP 993; misinterpreted by Bennett (1991, 1992) as belonging to a female Pteranodon). 

No reconstructions were provided
by Longrich, Martill and Andres 2018. Reconstructions and a nyctosaur blueprint might have helped these paleontologists with firsthand access to the specimens discover the issues they missed.

It’s good to know
more pterosaurs made it to the latest Cretaceous.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992.
 Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Longrich NR, Martill DM, Andres B 2018.
Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biol 16(3): e2001663. https://doi.org/10.1371/journal.pbio.2001663
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. 
The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

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