Largest ‘flying reptile’ from the Crato formation? Maybe not.

Cheng et al. 2018
report on a partial wing finger (MPSC R 1221, Fig. 1) that they say represents, “The largest flying reptile from the Crato Formation, Lower Cretaceous, Brazil.”

But is it? 

Figure 1. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221.

Figure 1. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221. If the scale bars are correct, the SMNS specimen is much larger.

No…
if the scale bars are correct. The larger, as yet undescribed, and very impressive SMNS PAL 1136 specimen (Fig. 1) is not mentioned in the text. I do not know if the SMNS specimen is from the Crato or Roualdo formation (I have not gone back to look up that datum). In any case, the authors overlooked this specimen, because it is not mentioned in the text or charts that list a few dozen other large pterosaurs. It should have been included. Of course, then the headline would have read, “…second largest…” and no one wants that.

So was this oversight intentional?
We’ll never know. The SMNS specimen has been in the literature for 24 years (Frey and Martill 1994).

Addendum several days later
The Crato Formation was not erected until 13 years after the 1994 paper by Martill, Bechly and Loveridge. Therefore all layers were considered Santana Formation in 1994. So the SMNS specimen from the Santana formation might have come from the upper or lower layers. It should have been included in the 2018 survey.

The authors conclude
“Based on the fusion of the extensor tendon process and the first wing phalanx and bone histology, MPSC R 1221 presents a subadult individual of a late ontogeny stage (OS5) at time of death, whichmeans that the final maximized wingspan might have been larger. This is corroborated by the osteohistological sections since this individual did not present an external fundamental system.” Look how eager the authors are to hang on to that superlative, ‘largest’, even though we know of at least one that is so much larger.

The authors do not realize
or continue to deny data, that pterosaurs do not follow archosaur fusion patterns during ontogeny—because pterosaurs are not archosaurs, and their fusion patterns follow phylogenetic patterns.

I never heard the term,
“external fundamental system” before. So, I looked it up: “A closely spaced series of lines of arrested growth that is called the External Fundamental System (EFS) indicates that adult size has been reached.” Now we all know!

I hope this blog post
will one day turn out dozens of young paleontologists who will read every paper they see with a seasoned and skeptical eye. If so, a few of you may someday become editors of academic journals or manuscript referees. When that happens, don’t let mistakes like this slip out. Having a website, like ReptileEvolution.com, that is full of data and illustrations, makes it easy to fact-check superlative claims, like this one, with just a few clicks.

On that note:
here (Fig. 2) is a published illustration of a pterosaur wrist from Duque and Barret 2018 with labels that were a little mixed up with regard for the ulna and radius. The referees should have caught this.

Figure 1. From figure 9 from Duque and Barreto 2018 with corrections noted and digit 5 colorized

Figure 2. From figure from Duque and Barreto 2018 with corrections noted and digit 5 colorized. This mistake should have been caught by the authors and referees, not me.

References
Cheng X, Bantim RAM, Sayão JM, Kellner AWA, Wang X and Saraiva AAF 2018. The largest flying reptile from the Crato Formation, Lower Cretaceous, Brazil. Historical Biology. https://doi.org/10.1080/08912963.2018.1491567
Duque RRC and Barret AMF 2018. New exceptionally well-preserved Pterosauria from the lower Cretaceous Araripe Basin, Northeast Brazil. Cretaceous Research 10.1016/j.cretres.2018.05.004
Frey E and Martill DM 1994. A new Pterosaur from the Crato Formation (Lower Cretaceous, Aptian) of Brazil. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 194: 379–412.

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Battle of the giant Quetzalcoatlus sculptures

Bigger is better
especially when it comes to pterosaurs in museum exhibits. To wit: The Field Museum (Chicago, IL, USA) is installing a flying Quetzalcoatlus (Fig. 3) and a standing Quetzalcoatlus (largely imagined and restored, based on an almost complete wing bone, Fig. 1).

The artist/professors in Southern England
have one as well (Fig. 1). And full scale Q. northropi sculptures can be found worldwide! (See links and images at the end of this post.)

Figure 1. Field Museum Quetzalcoatlus (tan) vs. English Quetzalcoatlus (gray) vs. a tracing of the real Q. sp. and Q. northropi scant remains.

Figure 1. Field Museum Quetzalcoatlus (tan) vs. English Quetzalcoatlus (gray) vs. a tracing of the real Q. sp. and Q. northropi scant remains. Yes, the skull on the Field Musuem model is too long, evidently following the invalid archosaur hypothesis of origin. Pterosaurs, like other tritosaurs, do not change their proportions during growth as fossils demonstrate.

These models arrive on the heels
of a recent post on flightless giant pterosaurs. The Field Museum model (Fig. 1) appears to have a more precisely modeled skull, though about 50% too long (but really, without a skull, who knows?). Perhaps the skull was elongated (based on the smaller ?species) based on the invalid archosaur hypothesis of pterosaur origins. We know from the evidence of fossils that hatchlings and juvenile pterosaurs had adult proportions, not longer skulls.

Both models suffer
from putting too much weight on the tiny free fingers. The feet should be beneath the shoulder joint, as in birds, to take the weight off the tiny hyperextended fingers, acting more like ski poles, not providing thrust, only some sort of support.

The folded wing membrane should tend to disappear
(Fig. 2), but it shows in both models. The wing finger should flex closer to the elbow, but it doesn’t (probably to let the wing membrane show). The wing membrane chord should be shorter, to the elbow, but in both models the brachiopatagium blends with the leg, always awkwardly and in defiance of the data preserved in all pterosaur fossils (Fig. 2) that preserve soft tissue.

Here's how the wing membrane in pterosaurs virtually disappeared when folded.

Figure 2. Here’s how the wing membrane in pterosaurs virtually disappeared when folded. This is a tiny pre-azhdarchid, CM 11426.

Over at the Carnegie Museum (Pittsburgh, PA, USA)
they have a tiny pre-azhdarchid, CM 11426 (Fig. 2), with real wing membranes, as described above, matching those of other pterosaur soft tissues.

Figure 3. Field museum flying Quetzalcoatlus model has the invalid deep chord wing that attaches to the tibia.

Figure 3. Field museum flying Quetzalcoatlus model has the traditional but invalid deep chord wing that attaches to the tibia and makes this sort of pterosaur untenably awkward.

Figure 2. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. No wonder the results were odd. The math was wrong.

Figure 4. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. This is a possible slightly deeper wing chord. Compare this one to figure 5, which is more typical. And look at those hind limbs, like those of Sharovipteryx, forming a horizontal stabilizer, just like a typical airplane. And it matches the evidence (Fig. 2).

Not sure why pterosaur paleontologists
keep insisting that evidence (Fig. 2) can and should be ignored. It’s disheartening to see this and leaves them open to criticism.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 5. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate. Giant azhdarchids gave up flying by reducing the lenth of their wings, following the patterns of other flightless pterosaurs. There is no awkwardness with this narrow chord wing design, which follows fossils like CM 11426 (Fig. 2).

Other online Quetzalcoatlus models/sculptures:

Low Poly Quetzalcoatlus model

https://www.alamy.com/stock-photo-muenchehagen-germany-10th-apr-2017-a-sculpture-of-the-quetzalcoatlus-138149396.html

https://blog.everythingdinosaur.co.uk/blog/_archives/2014/07/07/collecta-quetzalcoatlus-with-prey-model.html

If some of these seem to defy the ability to fly based on
a too far aft center of lift and a too far forward center of balance, or too small of a wing for such a large mass, no worries mate! If the imagination can soar, then so can these giants (NOT!) In the above YouTube video, the invalid, but traditional batwing shape of the brachiopatagium is best seen in the pterosaur’s shadow.

Quetzalcoatlus northropi

Tierra de dinos - Quetzalcoatlus Northropi

IF the wing membranes seem encumbering
awkward, liable to trip up the pterosaur or catch on some low lying shrub, no worried, mate! As these pterosaurs once wandered, let your imagination wander. There’s no need to precisely follow the evidence (Fig. 2) that shows the wing membranes essentially disappearing while flexed/folded.

Quetzalcoatlus at the Toledo Zoo

It’s going to be difficult to raise the wings for flight
given some of these awkward quadrupedal poses. Much better to have the center of balance over the toes at all static times (see below), shifting the balance forward while running at full speed (Fig. 5), like birds.

http://www.iaapa.org/DigitalShowDaily/2016/wed/Billings.asp

https://hiveminer.com/Tags/quetzalcoatlus

Why is this Houston Museum Quetzalcoatlus posed like this? Very strange.

Why is this Houston Museum Quetzalcoatlus posed like this? Very strange.

Quetzalcoatlus neck poses. Dipping, watching and displaying.

Quetzalcoatlus neck poses from David Peters Studio. Dipping, watching and displaying. Yes, the third finger is wrong here. It should be pointing posteriorly.

With what we know about pterosaurs
this should be a golden age of restoration. Instead, these models will someday be seen for what they are… near misses. They replace elegance with awkwardness, facts with fancy, and precision with tradition.

References
https://blog.everythingdinosaur.co.uk/blog/_archives/2018/06/01/pterosaur-models-go-on-display.html

Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist 
Historical Biology 15: 277-301

Axial rotation: fingers in pterosaurs, toes in birds

A somewhat recent paper by Botelho et al. 2015
looked at the embryological changes that axially rotate metatarsal 1 to produce a backward-pointing, opposable, perching pedal digit 1 (= hallux).

Hallux rotation phylogenetically
Botelho reports: Mesozoic birds closer than Archaeopteryx to modern birds include early short-tailed forms such as the Confuciusornithidae and the toothed Enantiornithes. They present a Mt1 in which the proximal portion is visibly non-twisted, while the distal end is offset (“bent”) producing a unique “j-shaped” morphology. This morphology is arguably an evolutionary intermediate between the straight Mt1 of dinosaurs and the twisted Mt1 of modern birds, and conceivably allowed greater retroversion of Mt1 than Archaeopteryx.”

“D1 in the avian embryo is initially not retroverted9, and therefore becomes opposable during ontogeny, but no embryological descriptions address the shape of Mt1, and no information is available on the mechanisms of retroversion.”

Figure 1. Pes of the most primitive Archaeopteryx, the Thermopolis specimen.

Figure 1. Pes of the most primitive Solnhofen bird, the Thermopolis specimen. This digit 1 never left the substrate.

In Tyrannosaurus,
(Fig. 2) the entire metatarsal 1 with pedal digit 1 is rotated just aft of medial by convergence. It’s not axially rotated. It’s just attached to the palmar side of the pes. This pedal digit 1 was elevated above the substrate.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views. This digit 1 was elevated above the substrate.

In some birds
like the woodpecker, Melanerpes, and the unrelated roadrunner, Geococcyx, pedal digit 4 is also retroverted. Sorry, I digress.

Further digression
The axial rotation of pedal digit 1 in birds is convergent with the axial rotation of metacarpal 4 in Longisquama (Fig. 3) and pterosaurs. In both taxa the manus was elevated off the substrate and permitted to develop in new ways. Manual digit 4 never leaves an impression in pterosaur manus tracks… because it is folded, like a bird wing, against metacarpal 4. In Longisquama such extreme flexion is not yet possible.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs.

Figure 3. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized and the metacarpal is axially rotated, as in pterosaurs. Manual digit 5 is useless, but not yet a vestige. A pteroid is present, as in Cosesaurus. The coracoid is elongate as in birds. The sternum, interclavicle and clavicle are assembled into a single bone, the sternal complex, as in pterosaurs.

Note the lack of space between
the radius and ulna in Longisquama. This is what also happens in pterosaurs. It prevents the wrist from pronating or supinating, as in birds and bats… which means, the forelimb is flapping, not pressing against the substrate, nor grasping prey. That means all those images of Longsiquama on all fours are bogus. Now you know.

So now we come full circle
While the toes of birds axially rotate and the wing metacarpal of pterosaurs axially rotates, the forearms of birds, pterosaurs and Longisquama do not axially rotate. No one wants their wing to twist.

References
Botelho JF, Smith-Paredes D, Soto-Acuña S, Mpodozis J, Palma V and Vargas AO 2015. Skeletal plasticity in response to embryonic muscular activity underlies the development and evolution of the perching digit of birds. Article in http://www.Nature.com/Scientific Reports · May 2015 DOI: 10.1038/srep09840

More evidence for a narrow chord wing membrane in pterosaurs

Unidentified by a museum number
this beautifully complete and articulated Solnhofen (Late Jurassic) Rhamphorhynchus specimen (Figs. 1, 2) preserve outlines of soft tissue, including a narrow-chord wing membrane (supporting Zittel 1882; Schaller 1985; Peters 2002; contra Unwin and Bakhurina 1994; Elgin, Hone and Frey 2011).

Figure 1. Rhamphorhynchus specimen preserving soft tissue, including a narrow-chord wing membrane. For details see figure 2.

Figure 1. Rhamphorhynchus specimen preserving soft tissue, including a narrow-chord wing membrane. For details see figure 2.

A closer view reveals a wing-tip ungual
(Fig. 2) better presented when Photoshop increases the contrast in the photo. Note: the other wingtip is more buried. This one less so. You’re still seeing the matrix over the wingtip ungual. The preparators did not excavate the entire wingtip from either wing.

Also worthy of note:
the propatagium extends to the deltopectoral crest, not to the neck. Pedal digit 5 is not connected to the uropatagia or any other membrane. And there is no single deep chord uropatagium extending between the legs. The toes are also webbed in other specimens. Here those webs are covered by the brachiopatagium.

Figure 2. Closer view of the specimen in figure 1 with overlays showing the various membranes and wingtip ungual.

Figure 2. Closer view of the specimen in figure 1 with overlays showing the various membranes and wingtip ungual, here a little bit buried along with the tip of m4.4, probably expanding the apparent size of the wing tip, just as burying an arrowhead necessitates using more mud to cover the edges and smooth out the edges.

As documented
earlier, the deep chord wing membrane is never found in pterosaurs. Both Unwin and Bakhurina 1994 and Elgin, Hone and Frey 2011 used cartoonish outlines to fudge their data. And when Elgin, Hone and Frey 2011 could not fudge their data (e.g. the Zittel wing), their desperation to avoid confirming Peters 2002 forced them to claim ‘membrane shrinkage‘ when there was none. I’m not sugar-coating this. This is what some paleontologists do in the present age. Be ready for it when you enter this field.

Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Is this a case of confirmation bias?
Yes. But I have yet to see any examples that confirm any other interpretation. Please send them if you have them.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Prondvai E and Hone DWE 2009. New models for the wing extension in pterosaurs. Historical Biology DOI: 10.1080/08912960902859334
Schaller D 1985. Wing Evolution. In: Hecht, M., Ostrom, J.H., Viohl, G. and Wellnhofer, P., eds, The Beginning of Birds. Proceedings of the International Archaeopteryx Conference, Eichstätt 1984, (Freundes Jura Museum, Eichstätt),pp. 333–348.
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.
Zittel KA 1882. Über Flugsaurier aus dem lithographischen Schiefer Bayerns. Palaeontographica 29: 7-80.

http://reptileevolution.com/pterosaur-wings.htm
http://reptileevolution.com/pterosaur-wings2.htm
http://reptileevolution.com/rhamphorhynchus-wings.htm

 

Elgin 2014 PhD dissertation: nits and picks, part 2

Yesterday we looked at
a misidentified pterosaur specimen from the State Museum of Natural History Karlsruhe (SMNK) that wasn’t a Tupuxuara, as originally considered by then PhD candidate, now Dr. Ross Elgin. Consider that blogpost an unlabeled part 1.

Today, in part 2,
we’ll take a look at several other aspects of the Ross Elgin 2014 PhD dissertation that deserve credit and discredit. 

FIgure 1. GIF animation of image from Elgin 2014 comparing wing membrane configurations and a more accurate rendition of what Peters 2002 proposed. See text for list of issues here.

FIgure 1. GIF animation of image from Elgin 2014 comparing wing membrane configurations and a more accurate rendition of what Peters 2002 proposed and Elgin distorted. See text for list of issues here. In reality, like birds, the wings and hind limbs are decoupled. Most pterosaur workers don’t believe the data.

Elgin mistakenly reported,
“The primary flight membrane is reconstructed with an ankle attachment of the trailing edge, a configuration that was never fundamentally altered throughout the evolutionary history of the group.” Elgin ignored the bipedal origin of the Pterosauria, and ignored the narrow-chord wing membrane data that attends every pterosaur fossil that preserves wing membranes, perhaps on the advice of his mentors. And he ignored, or distorted, what Peters 2000 actually proposed for a wing membrane and bone orientation in pterosaurs (Fig. 1).  This may be what happens when you have to feed the fever dreams of a teacher rather than recording actual data. Elgin reported, “I am indebted to both David Hone and Eberhard “Dino” Frey for the opportunity to undertake this project and continue my work on the enigmatic and curious group of animals known as pterosaurs.”

Solutions to problems with Figure 1.

  1. The scapula/coracoid should rotate laterally, as in all articulated fossils
  2. The elbow should angle further posteriorly, as in all articulated fossils (+ in birds and bats)
  3. The pteroid should point to the deltopectoral crest, as in all articulated fossils
  4. The free fingers should point ventrally (in flight). Crushing typically rotates the narrow claws anteriorly.
  5. Metacarpals 1-3 should line up anteriorly, not stack themselves against mc4
  6. Manual 4.4 should articulate at an angle to m4.3, deepening the wing tip
  7. The propatagium should extend only to the deltopectoral crest
  8. The brachiopatagium should stretch between the wingtip and elbow with a fuselage fillet to distal thigh, as in all articulated fossils
  9. The thigh should be more meaty based on the long anterior ilium
  10. The femur should extend laterally to form a horizontal stabilizer (and note the sprawling lepidosaur orientation!)
  11. The femur should be flipped, as shown in Elgin’s figure 3 below.
  12. The uropatagia do not extend to the tiny tail, as in all articulated fossils. Elgin’s essentially creates a single uropatagium, which is a decades-old false paradigm.

If the above illustration by Elgin 2014 looks familiar
it’s because we looked at it earlier here, after publication of Elgin, Hone and Frey 2011. Also check out all the images on this ReptileEvolution page. You might remember these authors employed the fiction of ‘wing membrane shrinkage’ to explain the data, instead of just accepting the data, as is. We have evidence of pterosaur ancestors with wings decoupled from the hind limbs, so there was never a gliding transitional phase. Flapping preceded flying.

Along the same lines
Hone and Benton (2007, 2008); and Nesbitt and Hone (2010a, b) preferred to see things their own way, rather than strict adherence to the data. So, maybe young Elgin was unduly influenced by his professors and mentors.

Elgin introduced us to
Microtuban altivolan, which he described as a non-azhdarchid azhdarchoid. In the large pterosaur tree (LPT, 1189 taxa) Microtuban indeed nests at the base of the azhdarchid clade, arising from certain dorygnathids, a relationship Elgin never tested.

Elgin suggested a possible sexual dimorphism,
“where the pelvic girdle lacks a symphysis and remains open even in large adults is observed within Coloborhynchus robustus.” (Fig. 2) Let’s blame this one partly on his teachers, and partly on sloppiness. The base of the pterosaur pelvis opens and closes in phylogenetic patterns, not gender patterns. That tricked up Bennett, too, and Elgin’s teachers followed Bennett’s mistakes. On the sloppiness point, the open pelvis of C. robustus is missing its ventral and posterior borders, exactly the bones needed to join the ischia together (Fig. 2). It doesn’t look like Elgin was cheating. He must have thought he was not cheating. But he was cheating by changing points of view, changing scales and not adding back missing bone to follow generic patterns. This was all resolved with a little tracing in Adobe Photoshop, the paleontologists’ best friend.

Figure 1. Elgin compared these two Coloborhynchus pelves together, but failed to align them, scale them and add back missing bone.

Figure 2. Elgin compared these two Coloborhynchus pelves together, but failed to align them, scale them and add back missing bone.

Elgin was also tricked by
traditional archosaur patterns and paradigms in ontogeny. He expected sutures to close at adulthood. This tricked up Bennett, too. Instead, since pterosaurs are lepidosaurs, sometimes they do, sometimes they never do, and sometimes they fuse sutures before maturity and reading their final size. It’s all phylogenetic, not ontogenetic with lepidosaurs, including pterosaurs.

Figure 2. Coloborhynchus robustus (bones and outlines from Elgin 2014) compared to C. spielbergi (b&w). Notes added.

Figure 3. Coloborhynchus robustus (bones and outlines from Elgin 2014) compared to C. spielbergi (b&w). Notes added.

Elgin described and did not illustrate the missing wing finger:
“The wing finger phalanges in almost all pterosaurs are similar in form with expanded proximal and distal margins, the shafts of which show various degrees of curvature. Those preserved in SMNK PAL 1133 are not exception and agree well with other descriptions of pterodactyloids.” This description can only be the result of naiveté and inexperience. In reality phalanx proportions change between genera and species. It would have been helpful to see the wing finger of C. robustus since the C. spielbergi wing finger is missing.

Elgin 2014 mistakenly considered

  1. pterosaurs to be archosauromorphs.
  2. anurognathids to be basal pterodactyloids
  3. Darwinopterus to be ‘an animal intermediate’ linking basal to derived pterosaurs

These issues are resolved and settled
here and here when you add more taxa. It’s good for science to be critical. If nothing else this blog will hopefully show all readers that published scientific text and figures can sometimes include errors that can be exposed and corrected by colleagues.

It’s not okay
to disfigure the figures of other workers and then claim that’s the essence of their work (contra Fig. 1). We’ve seen this before with other PhDs.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Elgin RA 2014. Palaeobiology, Morphology, and Flight Characteristics of Pterodactyloid Pterosaurs. Innaugural Dissertation. Zur Erlangung der Doktorwürde Fakultät für Chemie und Geowissenschaften Institut für Geowissenschaften Ruprecht-Karls-Universität Heidelberg. Available online  here.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Nesbitt SJ and Hone DWE 2010a. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Nesbitt SJ and Hone DWE 2010b. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233

https://pterosaurheresies.wordpress.com/2012/04/13/a-supertree-of-pterosaur-origins-hone-and-benton-2007-2009/

http://www.reptileevolution.com/pterosaur-wings.htm

https://pterosaurheresies.wordpress.com/2011/11/18/did-dimorphodon-have-an-external-mandibular-fenestra/

https://pterosaurheresies.wordpress.com/2013/01/16/a-closer-look-at-the-antorbital-fossa-in-two-pterosaurs-raeticodactylus-and-dimorphodon/

Why do pterosaur workers ignore the most basic data?

I don’t know why,
but today’s leading pterosaur experts are actively ignoring the data from the last twenty years while inventing their own fanciful versions of what pterosaurs looked like (Fig. 1) – while claiming to be the latest word on the subject. Today we’ll be looking at a short paper from the latest Flugsaurier book by Hone, Witton and Martill 2017. And we’ll criticize the artwork that crystalizes their latest intentions. This is part 1.

For some reason
Hone, Witton and Martill like to show ancient cartoons that have little to no bearing on the present knowledge base (Fig. 1). I think it’s an English thing since most, if not all of the old engravings are indeed English in origin and easily lampooned. ‘See how far we’ve come!’, they seem to be saying. Doing so only takes up space that could otherwise go to competing current versions – which they want to avoid.

We’ve seen this
earlier when English professor D. Naish preferred to criticize work that preceded (= was not included in) ReptileEvolution.com. He employed cartoons made by others, rather than artwork that was actually posted on the website to show how bad the whole website was.

Evidently
It’s what they like to do. Someday, perhaps, they’ll look in a mirror and see some of the faults I present here… using their own artwork – which will soon enough joint their ancient engravings in a drawer full of foolish ideas they can draw upon in future decades.

Figure 1. Images from Hone, Witton and Martill 2017 showing the 'evolution' of our concept of Dimorphodon. Compare the latest color version to tracings of the several skeletons in figure 2.

Figure 1. Images from Hone, Witton and Martill 2017 showing the ‘evolution’ of our concept of Dimorphodon. Artists are credited in the text. Compare the latest color version to tracings of the several skeletons in figure 2. The long tail is based on a disassociated fossil probably belonging to a campylognathoid.

In figure 1
images of Dimorphodon through time are presented from Hone, Witton and Martill 2017.

  1. Rev. GE Howman 1829. Probably based on the headless holotype BMNH R1034 (Fig. 2). The authors labeled this as ‘monstrous’ when ‘inaccurate’, ‘fanciful’ or ‘medieval’ would do.
  2. Owen 1870. Probably based on the short-skull specimen, BMNH 41212 (Fig. 2), along with the disassociated tail specimen. The authors labeled this rendition as ‘ungainly, bat-like’. Odd word choice when among all the presented illustrations it is the one most like Witton’s 2017 version (#5).
  3. H Seeley 1901. Probably based on the long-skull specimen, BMNH PV R 1035 (Fig. 2) In the their comment Hone, Witton and Martill report, ‘progressive interpretation of D. macronyx as an erect-limbed quadruped’, but note that a biped interpretation was also offered. They thought it best not to show that possibility. 
  4. K Padian 1983. Probably based on the short-skull specimen, BMNH 41212 (Fig. 2). The authors report, ‘a highly active, bird-like digitigrade biped, a controversial interpretation that nevertheless symbolises the reinvention of pterosaurs in the late twentieth century.’ While there are minor issues associated with this figure (the orientation of fingers 1–3 and pedal digit 5, the over-extension of the metatarsophalangeal joint, the great length of the tail), it is the one that is most closely based on the skeleton (Fig. 2). BTW, when authors use the word, ‘controversial’ it usually means it does not fit their world view, but they have no evidence against it, nor any evidence to support their traditional hypothesis. 
  5. M Witton 2017. Not sure which skeleton this one is based on as it appears to have been done entirely freehand from memory and imagination. The authors report, ‘Modern interpretation of D. macronyx adult and speculative juveniles reflecting contemporary interpretations of pterosaur soft tissues, muscle development and ecology.’ Ahem…we’ll run through this illustration step-by-step below.
Figure 2. Images of Dimorphodon from ReptileEvolution.com. The tail attributed to Dimorphodon is shown in figure 3.

Figure 2. Images of Dimorphodon from ReptileEvolution.com. The tail attributed to Dimorphodon is shown in figure 3.

You know, you really can’t go wrong
when you strictly adhere to the bones (Figs. 2,3), soft tissue (Peters 2002) and footprints of the most closely related taxa (Peters 2011), which were made by digitigrade and bipedal pterosaur trackmakers. Unfortunately no such citations appear in this chapter. Those are purposefully omitted.

Dimorphodon model by David Peters

Figur 3. Dimorphodon model by yours truly. The tail is too long based on the disassociated tail.

Witton
fell under the spell of the quad-launch hypothesis (Habib 2008), then took it one step further and made Dimorphodon a galloping hunter (Fig. 4), forsaking its wings and erect, digitigrade hind limbs (according to related ichnite makers) to hunt prey on mossy logs with backward pointing fingers. The finger unguals are again too small here.

While writing this I became aware
of Sangster 2003, a PhD thesis that evidently used computer modeling to show Dimorphodon was a quadruped. I have not seen the thesis and Ms. Sangster can no longer be found online. I wonder about these conclusions because:

  1. PhD theses are, by definition, the work of inexperience workers; and
  2. Sangster may have had to earn her PhD by succumbing to the unveiled interests of her English professors, as we’ve seen before here and here.
Figure 4. Galloping Dimorphodon by Mark Witton.

Figure 4. Galloping Dimorphodon by Mark Witton.

To counter the awkward, dangerous and ultimately unproductive
quad-launch scenario, I proposed the following bipedal launch animation (Fig. 5). It combines the hind limb leap with the first flap of the large wings to provide the maximum thrust at takeoff. In the Habib proposal, you don’t get that wing flap until later in the cycle – maybe too late in the cycle. The quad launch also depends on directing the force of liftoff through the fragile free fingers. They were not strong enough for that, especialy not when there is a better option available using giant muscles in the chest and pelvis. That’s why the sacrum is so strong, to act as a fulcrum on that long, heavy lever!

FIgure 5. Dimorphodon take off (with the new small tail).

FIgure 5. Dimorphodon take off (with the new small tail).

So let’s get back
to Witton’s cover illustration (Fig. 6), which they tout as our contemporary view of Dimorphodon. I will note several inaccuracies (below). See figures 2 and 3 for accurate tracings.

Figure 6. Touted as the contemporary view of Dimorphodon, this Mark Witton illustration suffers from several fancies and inaccuracies.

Figure 6. Touted as the contemporary view of Dimorphodon, this Mark Witton illustration suffers from several fancies and inaccuracies.

  1. No Dimorphodon as this shape of skull.
  2. Needs a longer neck.
  3. Free fingers should be long and the unguals much larger.
  4. Wing appears to be too short with a too narrow wing tip chord.
  5. Witton wants to connect the trailing edge membrane from wing tip to ankle (or lateral toe), but look at the tremendous stretch in the membrane when that happens. Seems to be getting dangerously close to the narrow-at-the-elbow wing design of Zittel, Schaller and Peters, which they want to avoid.
  6. Ouch! This is a set of elongate toe bones with butt metatarsophalangeal joints – where Witton breaks them. This is not a calcar (a novel ossification on bat ankles which enters the uropatagium). One one side of these lateral toes the wing membrane attaches. On the other side the uroropatagium attaches. This is not shown in any fossil! Related taxa, from Langobardisaurus to Sharovipteryx, to Tanystropheus, with this same sort of elongate toe morphology, do not dislocate their bones this way. See Peters 2000 for a description that fits Rotodactylus tracks.
  7. No pterosaur has a uropatagium. This comes from a misinterpretation of Sordes. Pterosaur do have paired uropatagia.
  8. The tail is too large. On the BMNH 41212 fossil the traditionally overlooked tail is very small (Figs. 2, 7) This is in accord with related anurognathids. An unassociated tail has been attributed to Dimorphodon (Fig. 5) but it is robust and much longer. It probably belongs to a eudimorphodontid or campylognathoid. I”m surprised the tiny tail of Dimorphodon has gone unnoticed for so long. The specimen has been in English storage for over a hundred years. It was their responsibility for discovering this, but they chose instead to use their imaginations (Fig. 6).
  9. No tail vane is known for Dimorphodon. Tail vanes are found in pterosaurs like Campylognathoides and Rhamphorhynchus, both with a robust tail. Vestigial tails are unlikely to have had tail vanes.
FIgure 7. The tail of Dimorphodon (BMNH 41212 specimen). See figure 2 for reconstruction.

FIgure 7. The tail of Dimorphodon (BMNH 41212 specimen). See figure 2 for reconstruction.

I’m asking my Engllsh colleagues
|to step up their game and become more professional. Otherwise chaps from across the pond are going to continue pointing out the flaws in their thinking. I’m not going to say their approach is not scientific (as they say about my work), but when you forsake accuracy for artistry, you’re treading very close to that line.

References
Habib MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana B28:159-166.
Hone DWE, Witton MP and Martill DM 2017.
New perspectives on pterosaur paleobiology in Hone DWE, Witton MP and Martill DM (eds) New Perspectives on Pterosaur Palaeobiology. Geological Society, London, Special Publications, 455, https://doi.org/10.1144/SP455.18
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods 
Ichnos, 7: 11-41.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist 
Historical Biology 15: 277-301
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification.
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Sangster S 2003. The anatomy, functional morphology and systematics of Dimorphodon macronyx (Diapsida: Pterosauria)..Unpublished PhD thesis, University of Cambridge.

Glide analysis in hatchling pterosaurs

Witton et al. 2017 report in their abstract:
We found that hatchling pterosaurs were excellent gliders, but with a wing ecomorphology more comparable to powered fliers than obligate gliders.”

Since hatchling pterosaurs were scale models of adults,
and adults were powered fliers, the logic follows. Oddly, Witton wrote a book in which this was not the case when he imagined a pre-hatchling Pterodaustro with a short rostrum and big eyes.

Witton et al. 2017 continue:
“Size differences between pterosaur hatchlings and larger members of their species dictate differences in wing ecomorphology and flight capabilities at different life stages, which might have bearing on pterosaur ontogenetic niching.”

Big science words here say nothing concrete. 
Dictate different flight capabilities: no. Dictate different prey items: yes.  Note the weasel word: “might have bearing” which acts like a nail in a tire to deflate everything said after it. Try to avoid using weasel words.

References
Witton M, Martin-Silverstone E and Naish D 2017. Glide analysis and bone strength tests indicate powered flight capabilities in hatchling pterosaurs. https://peerj.com/preprints/3216/