YPM VP057103: neither Dromicosuchus nor Poposaurus

Revised March 31, 2020
with the realization that the postfrontal and postorbital of the YPM specimen were fused, the quadrate was dislodged from its anterior lean and the restoring of several other traits that now nest this taxon with wider-skulled Orthosuchus (Fig. 2), both of which had binocular vision due to somewhat forward-facing orbits.

Figure 1. YPM VP 057 103 skull in situ, traced with colors using DGS methodology and reconstructed.

Figure 1. The well-known skull of tiny Orthosuchus. Note the concave maxilla and dentary, resulting in a large gap.

Figure 1. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades.

Identified online
by Brian Switek in 2016 on Twitter Fossil Friday as Poposaurus (Fig. 6), and published by the Yale Peabody Museum as cf. Dromicosuchus (Fig. 4) by Sterling Nesbitt 2018, specimen YPM VP 057 103 (Figs. 1–3) nests in the large reptile tree (LRT, then 1342 taxa, now 1660+ taxa) as a member of the Crocodylomorpha, close to Dromicosuchus, but closer to Orthosuchus.

FIgure 2. YPM VP 057 103 in situ with bones colored and reconstructed skull shown alongside.

Notable traits in the YPM specimen:
The premaxilla was elevated and pointed anteriorly forming a shark-like nose. The rostrum was elongate. The cervicals are longer than in sister taxa. The pubis may have curved posteriorly, as in another quadruped, Trialestes (Fig. 5), which led to earlier confusion. Distinct from sister taxa (and most tetrapods), the humerus was much longer than the femur in the YPM specimen. This basal crocodylomorph with long limbs and a short torso appears to have been able to gallop rapidly, something a few extant crocs are able to do.

Figure 3. YPM VP 057 103 reconstructed using color tracings from figures 1 and 2 in two scales. The smaller one shows the tail attached.

The skull of the YPM specimen
does indeed remind one of Dromicosuchus (Fig. 4), but the skull of the YPM specimen all by itself can nest it with basal crocs in the LRT, 20 steps apart from Dromicosuchus.

Figure 4. Dromicosuchus makes a first appearance here at PH.WP.com. Note the similarities to the YPM specimen. Phylogenetic analysis nests the YPM specimen apart from Dromicosuchus by 20 steps.

Poposaurus (Fig. 6) has distinctly different proportions. Likely the identification of this specimen changed behind the scenes between 2016 and 2018. Someone should mention this to Brian Switek so he can make an edit to his Twitter account.

Figure 6. Revised skull reconstruction for the PEFO specimen. Here the anterior is considered a premaxilla. Those teeth are shaped like triangles, but they are very deeply rooted and exposed very little, which casts doubts on its hypercarnivory.

References:
http://collections.peabody.yale.edu/search/Record/YPM-VP-057103

 

SVP 2018: Study says: Hatchling Massospondylus a likely biped

Earlier we looked at a Massospondlylus embryo and a reconstruction that appeared to be quadrupedal based on various limb and torso proportions (Fig. 1).

FIgure 1. Massospondylus carinatus embryo in situ and reconstructed.

Chapelle et al. ((3 co-authors) 2018 report,
“Our results clearly show that M. carinatus was a biped from hatching, and possessed bipedal skeletal proportions even in ovo.”

This is a judgement call. Up to you.

References
Chapelle KE, et al. 2018. Locomotory shfits in dinosaurs during ontogeny. SVP abstracts.

Rapetosaurus: my what a big pubis you have!!

Rapetosaurus krausei
(Curry, Rogers & Forster, 2001) is a Late Cretaceous titanosaur sauropod that is known from several bits and pieces from 3 adults, plus the majority of a juvenile specimen (Fig. 1). Adult lengths are estimated up to 15 m.

Figure 1. Rapetosaurus in traditional quadrupedal and imagined bipedal poses. Here that giant pubis is carrying a big gut.

In the large reptile tree (LRT, 1293 taxa) Rapetosaurus nests with the much taller and longer Diplodocus. Rapetosaurus has a much larger pubis for no better reason than to help support its guts when bipedal.

Figure 2. Rapetosaurus skull compared to other sauropods. That long antorbital fenestra on Rapetosaurus appears to be a combination of the maxillary fenestra seen in Tapuiasaurus. Note: every facial bone has less bone in Rapetosaurus.

The down-turned snouts here
reflect their angle relative to the occiput and probably the semi-circular canals.

References
Curry Rogers K and Forster CA 2001. The last of the dinosaur titans: a new sauropod from Madagascar. Nature. 412: 530–534. doi:10.1038/35087566

https://en.wikipedia.org/wiki/Rapetosaurus

“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. 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, 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.

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.

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).

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 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.

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

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.

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.”

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.

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.

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 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.

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. 

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

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.

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 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 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.

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…

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 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

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 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.

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 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 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.

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. 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. 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 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. 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. 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 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 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.

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. 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

https://pterosaurheresies.wordpress.com/2015/03/10/the-evolution-of-the-sordes-wing-and-uropatagia-1971-to-2011/

ITunes disfigures Dimorphodon

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).

What’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.

When fingers bend backwards while walking

Primitively tetrapod fingers formed an anterior arc, extending forwards, supporting the body and helping to provide thrust to each step. In the majority of terrestrial tetrapods, this remains true, even if the fingers shorten, hyperextend and flex to become, for instance, complex cat paws.

Figure 1. Anisodon (formerly Chalicotherium). A knuckle-walker. Click for enlargement and attribution.

In only a few tetrapods do the fingers point backwards.
In most this occurs because the tetrapod has adopted the configuration of “knuckle-walking,” turning the hand dorsal side down, flexing the fingers, often to protect giant claws. Anisodon (formerly Chalicotherium), the platypus (Ornithorhynchus anatinus) and giant anteaters (Myrmecophaga tridactyla) are examples of these. Typically weight is put upon the second phalanges with the proximal phalanges acting as columns.

Apes
In ape-like primates the nails/claws are not so long, but the fingers are, so knuckle-walking helps them walk quadrupedally. Apes can even carry small objects this way. Chimps tend to extend the wrist while knuckle-walking. Apes do not, but form a column with the arm, wrist and metacarpals (hand bones) all aligned. This form is no doubt derived from brachiation in which the fingers support the weight while flexed around branches and the legs are secondarily used in locomotion.

Figure 2. Gorilla knuckle-walking. This enables the gorilla to carry things, and follows the natural curl of all brachiators. Click to enlarge and check attribution.

Then there are the pterosaurs…
Earlier we talked about the strange toe #5 of basal pterosaurs and fenestrasaurs, like Cosesaurus, and how it bent dorsal side down to create a small  impression in the substrate far behind the anterior four toes. Rotodactylus tracks preserve this form of toe knuckle-walking.

Finger #3 also created backwards impressions of their entire length in all quadrupdal pterosaur tracks by extension (palmar side down), no flexion. Sometimes finger #2 was angled as much laterally as posteriorly. Finger #1 often pointed laterally, which also makes it distinct among tetrapods. Rarely #1 pointed anteriorly. These we’ll take a closer look at now.

How does a forward pointing finger work?
We’ve all seen how forward-pointing toes work. They help extend the length of the push-off phase of the step-cycle. They help support the torso, shoulders, head and neck that arc out ahead. During the recovery phase of the step cycle the anterior digits flex to provide clearance, extending only at the last moment when the entire paw or hand plops down almost at once. Some forelimbs are digitigrade, so only the distal phalanges and sometimes only the unguals are in contact with the substrate.

Bipedalism brings on changes
Pterosaurs ancestral cousins, like Sharovipteryx, were bipeds. Based on the shapes of their locked down coracoids, their forelimbs transformed into flapping limbs before they began to elongate into wings. So when pterosaurs re-elongated their forelimbs after the basalmost pterosaur, they did so with the forearms locked into a neutral configuration (unable to supinate or pronate) so their fingers extended laterally (like yours do while clapping or flapping), not anteriorly (when you’re on all fours with a child on your back).

Like lizards
Pterosaurs were derived from tritosaur lizards. In arboreal lizards with elongated fingers we can see the joints don’t move exactly like hinges, but often have more spherical, rather than cylindrical metacarpophalangeal joints. This gives them the ability to cling more readily to any substrate shape. Pterosaurs had the same sort of fingers, especially at the metacarpophalangeal joint on finger #3. Lizards are not known for their grasping abilities, so it is doubtful that pterosaurs could carry a berry or a baseball (depending on size).

Figure 3. Pteraichnus nipponensis, a pterosaur manus and pes trackway, matched to n23, ?Pterodactylus kochi (the holotype), a basal Germanodactylus.

So, did the claw of #3 touch down first while pterosaurs walked quadrupedally?
It’s hard to say, but appears likely. It was often (but not always) longer than digits 1 and 2 and it would have been unnecessarily awkward to keep the claw elevated until the rest of the fingers had touched down. You can see (Fig. 3) that manual digit 3 was directed posteriorly whenever it touched down. To that point, digit 4 never made an impression, but was kept folded against the forelimb while walking due to an axially rotated metacarpal 4. To THAT point, maybe that’s why digit 3 extended backwards, directly beneath digit 4, which needed protecting.

Beachcombers, like Pterodaustro and Ctenochasma had small, weak manual fingers with small claws. Almost afterthoughts or vestiges by comparison.

Maybe pterosaur fingers didn’t flex (except to dig in the claws while tree perching), but acted like grappling hooks (if the claws were large) on trees. Pterosaurs with the largest fingers and claws, like Dimorphodon and Dorygnathus (Fig. 2), likely did not walk quadruped at all, but used their grappling hook unguals to grapple tree trunks. They have an inturned femoral head enabling parasagittal locomotion and were not far, phylogenetically, from their bipedal ancestors.

Figure 2. Dorygnathus on a tree, an example of pterosaur with large free fingers. This is the neutral configuration, neither supinated nor pronated. Here the flexibility of the metacarpophalangeal joint enabled the pterosaur to shift its position while grappling and to let the fingers find the right sort of bark to maximize adhesion. We’ll know Dorygnathus footprints when we find them because the manual digit 3 will impress longer than any of the digitigrade toes. 

If we ever find dimorphodontid trackmarks, I’m going to guess the claws will be turned toward the palm in a sort of pterosaurian knuckle walk, if the fingers touch down at all.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Air Giants (Habib) – YouTube Video of Royal Tyrrell Museum Lecture Series

The Royal Museum Lecture Series for 2012 featured as one of its speakers, Dr. Mike Habib of Chatham University and placed both the video and audio on YouTube. You can see it for yourself here. Dr. Habib is a good speaker, very entertaining, informative and knowledgeable. He is famous for his skeletal strength studies using beam analysis. This led Habib to his famous forelimb leap launch hypothesis. I blogged earlier on the seven problems found with that hypothesis, including falsifying the data on the hands of its subject matter, the pterosaur Anhanguera.

Habib reports all pterosaurs were quadrupedal, ignoring two reports (Peters 2011, Kim et al. (2012) on bipedal pterosaurs.

Habib reports the wing membrane attached to the ankle, shin or closer to the thigh. This was falsified earlier. Like dinosaur tail draggers, it’s an old idea without any evidence that refuses to die.

On the positive side, Habib compared the humerus and femur cross sections of a small owl with the humerus of an azhdarchid pterosaur, only a few millimeters thick (which is why it is nearly impossible to age such pterosaurs because the earlier layers are resorbed and disappear). He noted higher strength in the humerus compared to birds and less strength in the hind limb, the opposite of birds. Habib reported take-off is hind-limb driven in birds, with the majority of the launch forces coming from the hind limbs, even in tiny-footed hummingbirds where it is reduced to 50/50. The opposite is the case with most pterosaurs, according to Habib, with the forelimbs providing the initial takeoff push.

Habib reports you don’t get a lot of lift initially, which is why the hindlimbs are so important during takeoff in birds, bringing to mind a swimming competition and using the feet to kick off the wall. A vampire bat, by contrast, uses a forelimb launch to bound off the ground with plenty of time to unfold the wings and start the initial flap. This is the analog to pterosaur forelimb take-off, according to Habib.

Wing loading determines airspeed for launching. After feeding a vampire bat has wing loading similar to a larger bird or bat, Habib reported.

Using Quetzalcoatlus Habib calculated a 14.7 m/second launch velocity with a launch time of 0.59 seconds. He reports the flight motor is also the launch motor in pterosaurs, which is the reason why certain pterosaurs were able to become so much larger than birds. This is also why the forelimbs were so much stronger than the hind limbs in azhdarchids, according to Habib.

Habib considered birds, not pterosaurs, to be divers and seed eaters.  Both were arboreal predators. Only pterosaurs were hawkers and soaring giants. Habib does not note the similar sizes found in ornithocheirids, pelicans and albatrosses seen here.

Habib reported a 10,000 mile flight range non-stop for Quetzalcoatlus, similar to that of the much smaller Arctic common tern. Habib reports the earlier, smaller pterosaurs could have launched quadrupedally or bipedally. The question and answer period introduced some interesting subjects.

Taking off from water was blogged earlier.

What started a quadrupedal launch?
It’s [mathematically] better at overperformance during launch, reports Habib, but such a launch puts on additional constraints. Habib reported, since the membrane was attached to the lower leg that helps. He reports if bipedal with a broad wing membrane attached to the lower leg, you get an inappropriate angle of attack (too steep) and flutter in the trailing edge of the wing. Of course, this again ignores all the evidence for a narrow chord membrane and no evidence whatsoever for a deep chord.

Habib thought pterosaurs used anaerobic muscles to fly with. Such muscles provide more burst activity, but tire quickly. Aerobic muscles tend to sustain activity longer, oxygenated by a constant stream of respiration.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again. 

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Habib M 2012. Royal Tyrrell lecture series.
Kim JY, Lockley MG, Kim KS, Seo SJ and Lim JD 2012. Enigmatic Giant Pterosaur Tracks and Associated Ichnofauna from the Cretaceous of Korea: Implication for the Bipedal Locomotion of Pterosaurs. Ichnos 19 (1-2): 50-65.DOI:10.1080/10420940.2011.625779 online
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
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