Anhanguera animation at the NHM (London)

This one started off with so much promise
as the animators at the National History Museum (NHM) in London assembled their version of the ornithocheirid pterosaur, Anhanguera, bipedally (Fig. 1), as you’ll see when you click on the video under ‘References’.

Figure 1. Animated by the NHM, Anhanguera is bipedal and flapping its literally oversize wings.

Figure 1. Animated by the NHM, Anhanguera is bipedal and flapping its literally oversize wings standing on oversize feet with an undersized skull and hyperextended elbows and unbalanced stance.

Unfortunately there were some morphology issues (compared in Fig. 2):

  1. wings too long
  2. sternal complex missing
  3. gastralia missing (but rarely preserved in ornithocheirids)
  4. feet way too big
  5. skull too small
  6. tail too short
  7. not sprawling
  8. free fingers too big
  9. wing fingers should tucked tight against elbows (in the same plane)
  10. one extra cervical
  11. anterbrachia too short and gracile
  12. elbows overextended (in Fig. 1)
  13. too much weight put on forelimbs, center of balance (wing root) should be over the toes
  14. Prepubes are extremely rare in ornithocheirds, but when present they are tiny, putter-shaped and oriented ventrally in line with the bent femora, not anteriorly
Figure 2. NHM Anhanguera compared to skeletal image from ReptileEvolution.com.

Figure 2. NHM Anhanguera compared to skeletal image from ReptileEvolution.com. There are at least 10 inaccuracies here. See text for list.

Also unfortunately, the video quickly devolved
to the invalid and dangerous quad launch, when (doggone it!) it was all set up to do a more correct and  much safer bird-like launch. The laws of physics and biomechanics are ignored here, but at least David Attenborough narrates.

Figure 3. NHM Anhanguera quad launch select frames.

Figure 3. NHM Anhanguera quad launch select frames. The laws of physics and the limitations of biomechanics are ignored here.

Attempts to convince readers and workers
that the quad-launch hypothesis cheats morphology and physics (as recounted here and at links therein) have so far failed. But I’m not giving up. So, if anyone has a connection to the NHM in London, please make this post available to alert them of their accidental foray into wishful thinking and inaccurate morphology.

References
National History Museum (NHM) in London

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“Why we think giant pterosaurs could fly” (…NOT!)

Yesterday the Dinosaur Mailing List
linked a MarkWitton.com blogspot.com post titled, Why we think giant pterosaurs could fly.” It’s worthwhile looking (once again) at the arguments Dr. Witton most recently put forth to test them against the evidence presented by pterosaurs here at PterosaurHereseies. After all, it’s not fair to dredge up arguments Dr. Witton may have long ago abandoned. Alas, Dr. Witton is holding fast to his old arguments and pet hypotheses, many of which paint a false picture of pterosaur biology and behavior, based on evidence to the contrary (see below).

Dr. Witton precedes his arguments
with the admission that, “Giant azhdarchids are invariably known from scant remains, sometimes a handful of fragments representing bones from across the skeleton or, in the case of Quetzalcoatlus northropi, an incomplete left wing.” We looked at Q. northropi wing elements earlier here (Fig. 1). They are indeed scant, but nevertheless, impressive.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 1. Quetzalcoatlus specimens to scale. Q. sp. is also enlarged to the humerus length of Q. northropi. Gray zones are hypothetical and/or restored. Reduction of the wing, even in the smaller species, argues against flight in giant azhdarchid pterosaurs, as it does in much smaller flightless pterosaurs.

 

Dr. Witton reports,
…just a few bones can betray volant habits. It’s evident that even the largest pterosaurs bore wing anatomy comparable to their smaller, incontrovertibly flightworthy relatives. The huge deltopectoral crest…is a clear correlate for powered flight in giant species.” 

Unfortunately
Dr. Witton does not acknowledge the presence of any flightless pterosaurs (taxon exclusion). Flightless pterosaurs could test Dr. Witton’s ‘dp crest clear correlate’ hypothesis. Three flightless pterosaurs have been reported here based on their relatively short wings: SoS2428, PIN 2585-4, and Alcione (Fig. 2). Notably, all three have an unreduced deltopectoral crest.

Figure 2. Flightless pterosaurs, SOS24248, PIN2584-4, Alcione, to scale.

Figure 2. Flightless pterosaurs, SOS24248, PIN2584-4, and Alcione, to scale. Reducing the span of the wing is the easiest and most common way to become flightless in pterosaurs.

Wing length vs body size
provides the best argument for flightlessness in the case of SoS2428 (Fig. 3), itself a pre-azhdarchid. The same argument works for the other two flightless pterosaurs when comparisons to flighted sisters are presented.

Lateral, ventral and dorsal views of SoS 2428

Figure 3. Lateral, ventral and dorsal views of SoS 2428 alongside No. 42, a volant sister taxon. In dorsal view it becomes very apparent which one would be flightless.

Arthurdactylus

Figure 4. Arthurdactylus in dorsal view. Note the rather small deltopectoral crest in this taxon.

It’s a good time to remember
that hatchling pterosaurs had adult proportions. They were able to fly shortly after hatching. This also means that small to tiny pterosaurs had wing/body ratios comparable to those of the largest incontrovertibly flying pterosaurs, the ornithocheirids (Fig. 4) and pteranodontids. Notably, the deltopectoral crest of the ornithocheirid, Arthurdactylus, is relatively smaller than one would predict using Witton’s hypothesis, and quite variable in other members of this clade.

Dr. Witton reports,
“for large azhdarchids: their functional morphology and trackways show strong terrestrial abilities and they probably spent a lot of time grounded, only flying when harassed, or wanting to move far and fast. Indeed, in all likelihood giant pterosaurs couldn’t launch every few moments.”

Unfortunately
Dr. Witton does not consider the possibility that large azhdarchids could have employed wing thrust to hasten their getaways on the ground, like many large birds do (Fig. 5).

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 5. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

Witton and Habib 2010
used software designed to model bird flight to predict that giant azhdarchids could fly faster than 90 kph and were easily able to sustain long distance glides.

Witton reports: “The key to everything: quad launch”
and provided a helpful illustration (Fig. 6) to show the moment of takeoff. Remember, in pterosaurs the wing finger never makes an imprint, so the three tiny free fingers must bear some multiple of the entire weight of the pterosaur at the moment of lift-off, then the ventrally-oriented wing finger must circle around to provide at least one upward lift and one downward flap before the otherwise inevitable crash. Not even a heavily muscled kangaroo can lift itself to such a height on the first leap. Not even a body builder can perform such a push-up… but a tiny vampire bat can, and does so routinely.

Figure 6. In the 'quad launch' hypothesis, for which there is currently no fossil imprint evidence, the pterosaur does a sort of leaping push-up using its tiny free fingers to bear a multiple of its entire weight during the acceleration, without flapping, to takeoff speed.

Figure 6. In the ‘quad launch’ hypothesis, for which there is currently no fossil imprint evidence, the pterosaur does a sort of leaping push-up using its tiny free fingers to bear some multiple of its entire weight during the acceleration, without flapping, to takeoff speed. Then the dangerous part begins. The pterosaur has to swing its wings up and down to creat aerial thrust before crashing (see figs. 7, 8). The short humerus provides little leverage to do this. Among tetrapods, only tiny highly derived bats are able to succeed with this sort of takeoff scenario. All other pterosaurs flap first, then fly.

What happens
if pterosaurs don’t make altitude every time they attempt a launch? (Fig. 7) Calamity (Fig. 8). There is no room for error, no evolutionary path to perfection, even if possible. Can one enhanced pushup provide the necessary airspeed and altitude without wing assistance? Witton and Habib think so? Look what those giant wings have to do before contributing to thrust and lift. Much better to get those wing providing thrust and lift at the moment of takeoff, rather than waiting until, perhaps, too late.

Successful Pteranodon wing launch based on work by Habib (2008).

Figure 7. Successful Pteranodon wing launch based on work by Habib (2008). Best case scenario.

 

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 8. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Successful heretical bird-style Pteranodon wing launch

Figure 9. Successful heretical bird-style Pteranodon wing launch in which the hind limbs produce far less initial thrust because the first downstroke of the already upraised wing provides the necessary thrust for takeoff in the manner of birds. This assumes a standing start and not a running start in the manner of lizards. Note three wing beats take place in the same space and time that only one wing beat takes place in the Habib/Molnar model.

 

re: the pelvis
Witton reports, “The avian skeleton has two large girdles for limb muscles: an enlarged shoulder and chest region for flight muscles, and an enhanced pelvic region to anchor those powerful hindlimb launch muscles. Pterosaurs, in contrast, have only one large limb girdle – their shoulders, making this the de facto likely candidate for powering their launch cycles.”

Standing Pteranodon

Figure 10 Standing Pteranodon (the Triebold specimen). Note the robust and extended pelvis supported by at least nine sacrals.

It may be traditional to discount the pelvic region
of pterosaurs, but in all cases, the pelvis is also enhanced (Fig. 10) with fused sacrals, prepubes and an anteriorly expanded ilium anchoring powerful, and under appreciated muscles.

Ignoring evidence that does not serve a pet hypothesis.
Witton ignores the hard evidence of bipedal pterosaur trackways, when he quotes Habib 2008, who “also notes that launch in living tetrapod fliers correlates to terrestrial gait: the number of limbs used to locomote on the ground is the same as the number used to take-off. Birds walk and launch with two legs, while bats walk and launch using all four. An extensive record of pterosaur trackways shows that pterosaurs were quadrupedal animals like bats, and it stands to reason that they also launched from four limbs: they would contrast with our living fliers if they had to shift gaits to take off.” 

Witton calls the quad-launch
“the most efficient launch mechanism conceivable for a tetrapod,” ideal for such a strong humerus and such a weak femur. Julia Molnar produced a video of a quad launch.  You might remember that the Molnar pterosaur free fingers were incorrectly reduced (Fig. 11) and relocated to the dorsal (in flight) surface of the wing in order to get that big wing finger on the ground and ready to snap like a grasshopper’s hind limb. Yes, they cheated the anatomy to make their pet hypothesis work… and Dr. Witton warmly embraced, rather than pointing out its faults.

The so-called catapult mechanism in pterosaurs

Figure 11a. Left: The so-called catapult mechanism in pterosaurs. The fingers are in the wrong place and cheated small in order to let the wing finger make contact with the substrate – which never happens according to hundreds of pterosaur tracks. Right. The actual design of pterosaur (in this case Anhanguera/Santandactylus) fingers. Click to enlarge.

Errors in the Habib/Molnar reconstruction of the pterosaur manus

Figure 11b. Errors in the Habib/Molnar reconstruction of the pterosaur manus

 

The infamous animation by Molnar
(click to play YouTube video) apparently assumes a nearly weightless mass, a super powerful pushup, and a suspension of the moment of inertia required to drag that big pool stick of a wing finger around to the flying position after it has just been oriented ventrally to say nothing about the effects of drag while opening that less than aerodynamic wing membrane. Isn’t it better to completely extend that wing and set it in the upward position before launch?

Summary of points ignored by Dr. Witton

  1. The largest flying pterosaurs have the largest/longest wings
  2. Flightless pterosaurs do exist and they are identified by their short wings
  3. Flightless pterosaurs retain a large deltopectoral crest and continued flapping to provide thrust for fast getaways and threat displays
  4. The quad launch hypothesis was built on the false premise of wing finger contact with the substrate
  5. The quad launch is dangerous for its participant every time they perform it. Much better to generate wing thrust at the moment of takeoff, not some time later. Such takeoffs can be aborted or diverted without the danger of a crash landing.
  6. The quad launch hypothesis works well for small  bats, ankle high to a Dimorphodon (Fig. 12), which fly in a different fashion from other volant tetrapods, but this ability does not scale up well for giraffe-sized or other pterosaurs.
  7. Dr. Witton cherry-picks the data that fits his hypotheses and ignores data that invalidates the last few years of his work.
  8. Given the paucity of data at present for giant azhdarchids, it would have been appropriate to restore Q. northropi as flightless AND volant, and tell us where the dividing line would be if the missing bones were one way or the other, making comparisons to smaller azhdarchids and to other fully volant large pterosaurs, like ornithocheirids and pteranodontids.
  9. It would have been professional and appropriate for Dr. Witton to alert us to the (perhaps inadvertent) cheating Molnar and Habib did to their pterosaur manus (Fig. 11) before some rank amateur brought it to our attention, and not to adopt this bogus and untenable idea with such gusto (Fig. 6), perhaps out of friendship.
Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It's more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Figure 12. Dimorphodon and Desmodus (the vampire bat) compared in size. It’s more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters.  Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours, especially with giant finger claws.

At what stage(s) did azhdarchids lose the ability to fly?
If we just look at wing length (reduction of distal elements) then this clade appears to have become flightless at least twice (Fig. 13). In both instances that happens when the wing finger tip is no higher (when folded) than the dorsal rim of the dorsal vertebrae. And that happens the second time when azhdarchids double in size to standing over a meter tall. If valid, then the doubling and doubling in size of azhdarchids was possible because they gave up aerial pursuits in favor of a fully terrestrial and/or wading niche, as in the many giant flightless birds we are more familiar with.

Azhdarchids and Obama

Figure 13. Click to enlarge. Here’s the 6 foot 1 inch former President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our former President. The doubling and doubling again in size was made possible by giving up the constraints of flying. 

 

References
Habib MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana, 159-166.
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.

markwitton-com.blogspot.com/2018/05/
Seven problems with the quad launch hypothesis

Were early pterosaurs inept terrestrial locomotors?

Witton 2015 asked:
“Were early pterosaurs inept terrestrial locomotors?” Sorry, this online paper escaped my notice until now. It’s two years old.

The answer is
an unqualified “YES” when Witton turns perfectly good bipeds (supported by morphology, outgroups (Fig. 2), ichnites and omitted citations), into stumbling quadrupeds encumbered by imaginary wing membranes (Fig. 3) that connect the ankles and lateral pedal digits to the wing tips and binds the legs together with a single uropatagium. The Unwin influence is strong in those English youngsters. He also rotates the humerus in a shoulder joint that does not permit rotation (Fig. 1), which would be very bad for a flapping reptile, bird or bat.

Figure 1. Tracings from bones (on left) compared to Witton's freehand quads. Comments in red.

Figure 1. Tracings from bones (on left) compared to Witton’s freehand quads. Comments in red.

From the Witton abstract:
“Pterodactyloid pterosaurs are widely interpreted as terrestrially competent, erect-limbed quadrupeds, but the terrestrial capabilities of non-pterodactyloids are largely thought to have been poor.”

This may be true when you construct pterosaurs that don’t match footprints and you have no idea where ‘early pterosaurs’ came from, even though that has been known for 17 years. Obligate bipeds (Longisquama and Sharovipteryx) are outgroups. Basalmost pterosaur, Bergamodactylus (Fig. 2) , has longer hind limbs and shorter forelimbs (Fig. 2) than other pterosaurs, retaining these plesiomorphic traits.

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Figure 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus. Does this look like a quadruped to anyone? All derived pterosaurs have relatively shorter legs. Outgroups, whether the invalid Scleromochlus, or the valid Sharovipteryx, have long legs like these. Uropatagia are not preserved, but they are on a related taxa one node away, Sharovipteryx. Note the tail is NOT incorporated.

Witton’s abstract continues
“This is commonly justified by the absence of a non-pterodactyloid footprint record,”

(False, see Peters 2011)

“suggestions that the expansive uropatagia common to early pterosaurs”

(False, misinterpretation of Sordes)

“would restrict hindlimb motion in walking or running, and the presence of sprawling forelimbs in some species.”

(sprawling at the top, narrow gauge on the substrate (Fig. 3).

“Here, these arguments are re-visited and mostly found problematic. Further indications of terrestrial habits include antungual sesamoids, which occur in the manus and pes anatomy of many early pterosaur species, and only occur elsewhere in terrestrial reptiles, possibly developing through frequent interactions of large claws with firm substrates.”

Or possibly by grasping branches and tree trunks, but even that possibility is not considered or argued against by Witton.

Getting back to the uropatagium found in bats…
primitive bats extend a membrane from both legs back to the tail. Only in the most derived bats, like Desmodus (Fig. 3), is the tail a vestige to absent. The resulting uropatagium without the tail extends between the legs – while completely avoiding the toes. Thus the pterosaur/bat analog, is also bogus. Final point: basal bats don’t walk or run on their hind limbs. They hang. Only in bats like the vampire do some bats reacquire the ability to actively hop around on horizontal surfaces, like cow buttocks and grassy knolls.

Witton carefully avoids
any mention of papers in which bipedal pterosaur trackways are described (Peters 2011). He fully supports the uropatagium hypothesis proposed by Sharov 1971 and further supported by Unwin and Bakhurina 1994 (disputed by Peters 2002 and here). That uropatagium, found in no other specimens of Sordes or any other pterosaur, is really a displaced wing membrane (Figs. 3–5) along with a displaced radius and ulna as shown here. Note: a few days ago Witton’s latest illustration used pedal digit 5 to frame both the uropatagium and the brachiopatagium. No one else does this. No argument or explanation is given.

Figure 6. Above, from Witton 2017 focusing on the pterosaur uropatagium. Note: even though fanciful, it does not incorporate the tail, but goes from leg to leg, UNLIKE Desmodus the bat, which incorporates what little tail is left.

Figure 3. Above, from Witton 2017 focusing on the pterosaur uropatagium. Note: even though fanciful, it does not incorporate the tail, but goes from leg to leg, UNLIKE Desmodus the bat, which incorporates what little tail is left. Besides, their is NO homology here. Witton is trying to support a bad interpretation with a bad analogy. Not a good idea to support an analogy with invalid drawings. Witton gives no support through testing to the uropatagium controversy, but accepts it with blinders on.

Witton carefully avoids
any mention of other candidate pterosaur outgroups, like fenestrasaurs (Fig. 2), and the assistance they can offer to the questions posed, but supports the basal bipedal crocodylomorph, Scleromochlus, as a potential outgroup. Ironic, isn’t it?

My first question would be, which outgroup taxon has anything resembling a leg-spanning uropatagium?Certainly not phytosaurs. Nor any archosaur. Sharovipteryx has separate uropatagia, but in Witton’s world view those are not the same, nor are they to be mentioned, because that would involve citing some academic paper from Peters, which would be antithetical to Witton’s premise. In good science, all counterarguments are considered, attacked or supported.

The myth of the pterosaur uropatagium

Figure 4. The Sordes uropatagium is actually displaced wing material carried between the ankles by the displaced radius and ulna.

Witton supports
the invalid shrinkage hypothesis of Elgin, Hone and Frey (2011) to explain away narrow-chord wing membranes preserved in the fossil record…which would be ALL of them

The hind limbs and soft tissues of Sordes.

Figure 5. The hind limbs and soft tissues of Sordes. Above, color-coded areas. Below the insitu fossil. Note how insubstantial the illusory uropataigum is compared to the drawing that solidifies the area. Tsk.Tsk.

Witton reports,
“Trackways made by running pterodactyloids indirectly demonstrate how elastic their proximal membranes must have been, allowing track makers to take strides of considerable magnitude (Mazin et al., 2003) despite membranes stretching from the distal hindlimb to their hands (Elgin, Hone & Frey, 2011).” The other explanation is that the wings and hind limbs were always decoupled (as documented in all known fossils). Pterosaurs do not have a membrane extending to the ankles. Witton proposes a bounding gait for pterosaurs, even though no pterosaur tracks document this.

Figure 7. A plesiomorphic bat with the tail incorporated in the uropatagium. This bat, Myotis, cannot walk very well. Desmodus, highly derived, has required the ability to walk, but at the expense of its tail and a vestige uropatagium.

Figure 6. A plesiomorphic bat with the tail incorporated in the uropatagium. This bat, Myotis, cannot walk very well. Desmodus, highly derived, has required the ability to walk, but at the expense of its tail leaving a vestige uropatagium. Everything must be put into a phylogenetic context, even in analogies.

Thankfully Witton supports
“Assessments of pterosaur hindlimb muscle mechanics seem to confirm that the pterosaur pelvic and femoral musculoskeletal system is optimally configured for an erect stance.” 

But then he puts the fingers on the ground (Fig. 1). Why???

Perhaps Witton does not realize
what happens to his uropatagium when the pes is plantigrade, which is how Witton always reconstructs pterosaur pedes. Somehow he avoids drawing the lateral digit reversed toward the pelvis, as he proposed earlier.

Witton has no criticism
for one of his references, Hone and Benton 2007 (but did not cite the setup 2007 paper. Readers know, for many reasons, this is one of the worst papers ever published in this field. The facts will stun even freshmen paleontologists. 

Witton ignores the pterosaur sacrum,
which has more than the typical two sacrals found in a wide range of quadrupedal reptiles. Why does the pterosaur sacrum add and fuse vertebrae phylogenetically and more with larger taxa? For the same reason that humans, apes and theropod dinosaurs do. They are bipedal and the sacrum acts as the fulcrum to a long lever arm.

Earlier we talked about pterosaur workers wearing blinders, ignoring papers with hypotheses that conflicted with pet hypotheses. Now you see that happening in real time.

When workers, like Witton, stopped citing papers
I had published in academic journals is when I took my evidence and arguments online.

Earlier, in a multipart critique,
here, here, here, here and here we talked about Witton’s previously published work combined in a single book. I only wish someone with influence on Witton and his collaborators would remind them that their ideas and papers are going to end up like the Victorian-age cartoons they mock – unless they get back to facts and evidence.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeonntologica Polonica 56(1): 99-111.
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
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.
Witton MP 2015. Were early pterosaurs inept terrestrial locomotors? PeerJ 3:e1018 DOI 10.7717/peerj.1018

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.

One of the largest Pterodaustro specimens had stomach stones

aka: Gastroliths.
And that’s unique for pterosaurs of all sorts. So, what’s the story here?

Figure 1. The V263 specimen compared to other Pterodaustro specimens to scale.

Figure 1. The MIC V263 specimen compared to other Pterodaustro specimens to scale. Its one of the largest and therefore, most elderly.

One of the largest Pterodaustro specimens
MIC V263 (Figs. 1-5), was reported (Codorniú, Chiappe and Cid 2013) to have stomach stones (gastroliths). That made news because that represented the first time gastroliths have been observed in 300 Pterodaustro specimens and thousands of pterosaurs of all sorts.

Unfortunately,
Codorniu, Chiappe and Cid followed tradition when they aligned pterosaurs with archosaurs, like dinos (including birds) and crocs. Those taxa also employ gastroliths for grinding devices. According to Codorniú, Chiappe and Cid, other uses include as a personal mineral supply, maintaining a microbial flora, elimination of parasites and hunger appeasement. Shelled crustaceans may have formed a large part of the Pterodauastro diet and stones could have come in handy on crushing their ‘shells’ according to the authors.

FIgure 2. Pterodaustro specimen MIC V263 in situ and as originally traced.

FIgure 2. Pterodaustro specimen MIC V263 in situ and as originally traced.

The authors also noticed
an odd thickening of the anterior dentary teeth and the relatively large size of the MIC V 263 specimen (Fig. 1) and suggested their use as devices for acquiring stones.

The wingspan of this big Pterodaustro is estimated at 3.6 meters.

Figure 1. Pterodaustro elements from specimen MIC V263.

Figure 3. Pterodaustro elements from specimen MIC V263.

Unfortunately,
the authors overlooked a wingtip ungual (Fig. 4), or so it seems… The confirming wingtip ungula is off the matrix block. But they weren’t looking for it…

Figure 2. One wing ungual was preserved in this specimen of Pterodaustro. The other is missing off the edge of the matrix.

Figure 4. One wing ungual was preserved in this specimen of Pterodaustro. The other is missing off the edge of the matrix.

The authors overlooked a distal phalanges on the lateral toe (Fig. 5). It is hard to see. And they were not looking for it. Note the double pulley joint between p2.1 and p2.2. That’s where the big bend comes in basal pterosaurs.

Figure 5. Pterodaustro MIC V263 pes in situ and with pedal digit 2 reconstructed from overlooked bones.

Figure 5. Pterodaustro MIC V263 pes in situ and with pedal digit 2 reconstructed from overlooked bones.

The authors overlooked a manual digit 5, the vestigial near the carpus (Fig. 6) displaced to the disarticulated carpus during taphonomy. Again, easy to overlook. And they were not looking for it…

Figure 6. Carpus of the Pterodaustro specimen MIC V263 withe elements colorized. Manual digit 5 elements are in blue on the pink ulnare.

Figure 6. Carpus of the Pterodaustro specimen MIC V263 withe elements colorized. Manual digit 5 elements are in blue on the pink ulnare. Not sure where carpal 5 is.

The authors
labeled the unguals correctly (Fig. 7), but some of the phalanges escaped them. Note the manual unguals are not highly curved, like those of Dimorphodon and Jeholopterus. And for good reason. Pterodaustro is a quadrupedal beachcomber with the smallest fingers of all pterosaurs. It’s not a tree clinger. And for the same reason, pterosaurs with long curved manual claws are not quadrupeds. Paleontologists traditionally attempt to say all pterosaurs are quadrupeds, rather than taking each genus or clade individually. Beachcombers made most of the quadrupedal tracks. It’s also interesting to note that Pterodaustro fingers bend sideways at the knuckle, in the plane of the palm, probably in addition to flexing toward the palm. It’s easier for lizards to do this, btw. Not archosaurs. That’s how you get pterosaur manual tracks with digit 3 oriented posteriorly, different from all other tetrapods.

Figure 7. Pterodaustro MIC V 263 fingers reconstructed and restored.

Figure 7. Pterodaustro MIC V 263 fingers reconstructed and restored. Pterodaustro is unusual in having metacarpals 1 > 2 > 3. Note the flat tipped manual unguals. Not good for climbing trees, like those of many other pterosaurs.

So the question is: why did this specimen have stones inside—
when other pterosaurs do not? Since MIC V263 is larger, it is probably older, closer to death by old age. Was it supplementing an internal grinding structure that had begun to fail? Was this some sort of self-medication for a stomach ailment? It’s not standard operating procedure for pterosaurs to have stomach stones. So alternate explanations will have to do for now. Let’s not assume or pretend that all pterosaurs had gastroliths. They don’t.

Figure 8. Elements of the MIC V263 specimen applied to the smaller PPVL 3860 specimen scaled to the length of the metacarpals. At this scale the large Pterodaustro had a shorter wing and shorter fingers with smaller unguals.

Figure 8. Elements of the MIC V263 specimen applied to the smaller PVL 3860 specimen scaled to the length of the metacarpals. At this scale the large Pterodaustro had a shorter wing and shorter fingers with smaller unguals.

Compared to the largely complete and articulated Pterodaustro specimen,
PVL 3860, there are subtle differences in proportion (Fig 8) to the larger MIC V263 specimen. If metacarpals are the same length, then the wing is shorter in the larger specimen. This follows a morphological pattern in which no two tested pterosaurs are identical. Still looking for a pair of twins.

References
Codorniú L, Chiappe LM and Cid FD 2013. First occurrence of stomach stones in pterosaurs. Journal of Vertebrate Paleontology 33:647-654.

Pterosaur worker puts on blinders

Sorry to have to report this, but… 
Witton (2015) decided that certain published literature (data and hypotheses listed below) germane to his plantigrade, quadrupedal, basal pterosaur conclusions, should be omitted from consideration and omitted from his references.

Everyone knows, iI’s always good practice
to consider all the pertinent literature. And if a particular observation or hypothesis runs counter to your argument, as it does in this case, your job is to man up and chop it down with facts and data. That could have been done, but wasn’t. Instead, Witton put on his blinders and pretended competing literature did not exist. Unfortunately that’s a solution that is condoned by several pterosaur workers of Witon’s generation.

Not the first time inconvenient data
has been omitted from a pterosaur paper. Hone and Benton (2007, 2008) did the same for their look into pterosaur origins after their own typos cleared their way to delete from their second paper one of the two competing candidate hypotheses.

Witton (2013) and Unwin (2005) did the much the same by omitting published papers from their reference lists that they didn’t like.

Publication
is a great time to show colleagues that you have repeated all competing observations and experiments and either you support or refute them. To pretend competing theories don’t exist just increases controversy and reduces respect.

So, what’s this new Witton paper all about?

From the Witton abstract: Pterodactyloid pterosaurs are widely interpreted as terrestrially competent, erect-limbed quadrupeds, but the terrestrial capabilities of non-pterodactyloids are largely thought to have been poor (false). This is commonly justified by the absence of a non-pterodactyloid footprint record (false according to Peters 2011), suggestions that the expansive uropatagia common to early pterosaurs would restrict hindlimb motion in walking or running (false), and the presence of sprawling forelimbs in some species (not pertinent if bipedal).

“Here, these arguments are re-visited and mostly found problematic. Restriction of limb mobility is not a problem faced by extant animals with extensive fight membranes, including species which routinely utilize terrestrial locomotion. The absence of non-pterodactyloid footprints is not necessarily tied to functional or biomechanical constraints. As with other fully terrestrial clades with poor ichnological records, biases in behaviour, preservation, sampling and interpretation likely contribute to the deficit of early pterosaur ichnites. Suggestions that non-pterodactyloids have slender, mechanically weak limbs are demonstrably countered by the proportionally long and robust limbs of many Triassic and Jurassic species. Novel assessments of pterosaur forelimb anatomies conflict with notions that all non-pterodactyloids were obligated to sprawling forelimb postures. Sprawling forelimbs seem appropriate for species with ventrally-restricted glenoid articulations (seemingly occurring in rhamphorhynchines and campylognathoidids). However, some early pterosaurs, such as Dimorphodon macronyx and wukongopterids, have glenoid arthrologies which are not ventrally restricted, and their distal humeri resemble those of pterodactyloids. It seems fully erect forelimb stances were possible in these pterosaurs, and may be probable given proposed correlation between pterodactyloid-like distal humeral morphology and forces incurred through erect forelimb postures. Further indications of terrestrial habits include antungual sesamoids, which occur in the manus and pes anatomy of many early pterosaur species, and only occur elsewhere in terrestrial reptiles, possibly developing through frequent interactions of large claws with firm substrates. It is argued that characteristics possibly associated with terrestrially are deeply nested within Pterosauria and not restricted to Pterodactyloidea as previously thought, and that pterodactyloid-like levels of terrestrial competency may have been possible in at least some early pterosaurs.”

Bottom Line: Unfortunately Witton paid little attention to
the literature on non-pterodactyloid ichnites and feet. And he ignored certain basic tenets.

Witton writes: “Given that likely pterosaur outgroups such as dinosauromorphs and Scleromochlus bore strong, erect limbs (e.g.,Sereno, 1991; Benton, 1999), it is possible that these early pterosaurs retained characteristics of efficient terrestriality from immediate pterosaur ancestors.”

Wrong as this ‘given’ supposition is, both of the above taxa (dinos and scleros) are bipedal, yet Witton refuses to consider this configuration in basal pterosaurs (for which he claims have no ichnite record).

Figure 1. Witton's errors with a quadrupedal Preondactylus. For a study on terrestrially, there is little effort devoted to the feet of pterosaurs here.

Figure 1. Witton’s errors with a quadrupedal Preondactylus. For a study on terrestrially, there is little effort devoted to the feet of pterosaurs here. Click to enlarge.

Digitigrady vs. plantigrady
Pterosaur feet come in many shape and sizes. Some have appressed metatarsals. Others spread the metacarpals. These differences were omitted by Witton. Some have a very long pedal digit 5. Others have a short digit 5. These differences were also omitted. Some pterosaurs were quadrupeds (but not like Witton imagines them), others were bipeds (Figs. 1-6). Basal pterosaurs had a butt-joint metatarsi-phalangeal joint, but that just elevates the proximal phalanges, as confirmed in matching ichnites.

Figure 2. Witton's quadrupedal Dimorphodon.

Figure 2. Witton’s quadrupedal Dimorphodon. Click to enlarge.

The quadrupedal hypothesis is a good one,
but it really only works in short-clawed plantigrade clades that made quadrupedal tracks on a horizontal substrate. Otherwise a quadrupedal configuration works only on vertical surfaces, like tree trunks, where the trenchant manual claws can dig into the bark. This was omitted by Witton.

Figure 3. Dimorphdon toes and fingers. Here, in color, I added the keratinous sheath over the claws that show how ridiculous it would be for Dimorphodon to  grind these into the ground. Better to use those on a vertical tree trunk.

Figure 3. Dimorphdon toes and fingers. Here, in color, I added the keratinous sheath over the claws that show how ridiculous it would be for Dimorphodon to grind these into the ground. Better to use those on a vertical tree trunk (figure 2). Click to enlarge.

Quadrupedal pterosaurs can’t perch
on narrow branches. Peters (2000) showed how a long pedal digit 5 acted like a universal wrench for perching.

Figure 1. Anurognathus  by Witton along with an Anurognathus pes and various anurognathid ichnites.

Figure 4. Anurognathus by Witton along with an Anurognathus pes and various digitigrade anurognathid ichnites, all ignored by Witton. Digit 5 behind the others is the dead giveaway.

Quadrupedal pterosaurs can’t open their wings
whenever they want to, for display or flapping. Witton favors the forelimb launch hypothesis for pterosaurs of all sizes, forgetting that size matters.

Figure 5. Quadrupedal Rhamphorhynchus by Witton (below) with errors noted and compared to bipedal alternative.

Figure 5. Quadrupedal Rhamphorhynchus by Witton (below) with errors noted and compared to bipedal alternative.

Pterosaurs were built for speed
whether on the ground or in the air. They were never ‘awkward.’ Remember basal forms have appressed metatarsals, they have more than five sacrals, their ichnites are digitigrade, the tibia is longer than the femur, the bones are hollow, when bipedal the feet plant below the center of balance at the wing root, and some pterodactyloid tracks are bipedal.

Figure 6. Quadrupedal Campylognathoides by Witton (center) with errors noted and compared to bipedal alternatives.

Figure 6. Quadrupedal Campylognathoides by Witton (center) with errors noted and compared to bipedal alternatives. The lack of accuracy in Witton’s work borders on cartoonish.

Accuracy trumped by imagination
By the present evidence, Witton has not put in the effort to create accurate and precise pterosaur reconstructions. Rather his work borders on the cartoonish and I suspect the reconstructions have been free-handed with missing or enigmatic parts replaced with parts from other pterosaurs. That should be unacceptable, but currently such shortcuts are considered acceptable by Witton’s generation of pterosaur workers.

The Sordes uropatagium false paradigm gets a free pass
and no critical assessment from Witton. (So far this uropatagium has been observed only in one specimen, Sordes (in which a single uropatagium Witton believes was stretched between the two hind limbs), was shown to be an illusion caused by bone and membrane dislocation during taphonomy. All other pterosaurs and their predecessors have twin uropatagia that do not encumber the hind limbs. The dark-wing Rhamphorhynchus (Fig. 5) is an example of a basal pterosaur with twin uropatagia.

References
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.
Peters D. 1995. Wing shape in pterosaurs. Nature 374, 315-316.
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: 293-336.
Peters, D. 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Peters, D. 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
Peters, D. 2009. A Reinterpretation of Pteroid Articulation in Pterosaurs – Short Communication. Journal of Vertebrate Paleontology 29(4):1327–1330, December 2009
Peters, D. 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500
Peters, D. 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141.
Peters, D. 2010-2015. http://www.reptileevolution.com
Unwin DM 2005. The Pterosaurs: From Deep Time. Pi Press, New York.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.
Witton MP 2015.Were early pterosaurs inept terrestrial loco motors? PeerJ 3:e1018<
doi: https://dx.doi.org/10.7717/peerj.1018

ITunes disfigures Dimorphodon

Figure 1. ITunes SM Dinosaurs Dimorphodon. In a word: "awkward." Credit does go to the narrow chord wing membrane.

Figure 1. ITunes SM Dinosaurs Dimorphodon. Upper image, not too bad. Lower image, awkward. Is it getting ready to leap with forelimbs? Pedal digit 5 is useless here.  Tail vanes are unknown in dimorphodontids. Fingers appear too small. Credit goes to the narrow chord wing membrane. Let’s hope the wing finger is short due to foreshortening, but why run with the wing finger deployed? Image lightened to show detail.

Apple ITunes
is offering a dino app. Unfortunately it includes a badly configured Dimorphodon (Fig. 1) in a quadrupedal pose with hands far ahead of the shoulders. Perhaps it is getting ready to launch with forelimbs. While the Seeley inset was the inspiration, the app image takes it over the top. Missing a few fingers apparently and they’re too small as is. Great color and texture!

Here’s what Dimorphodon should look like: (Fig. 2).

Dimorphodon588What’s wrong with a bipedal Dimorphodon?
Like theropod dinosaurs, it has a right angle femoral head, appressed metatarsals, and long fingers with trenchant claws not well made for touching the ground. Sure the arms are long enough to reach the ground, but why should it? The closest known pterosaur tracks are single pedal ichnites matching anurognathids (Peters 2011).

References
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos, 18: 2, 114-141.