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 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus.

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

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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.

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.

Chalicothere220

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.

Gorilla knuckle-walking.

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

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.

Dorygnathus on a tree.

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

The Case Against Bipedal Pterosaurs

Two Camps
The subject of pterosaur bipedality remains contentious. In the modern era, Stokes (1957 attributed odd quadrupedal tracks to pterosaurs. For the next 25 years no one argued against it. Then Padian and Olsen (1983) determined that Pteraichnus tracks were crocodilian in origin. This convinced several other paleontologists along the way (Unwin 1989). In 1995 two papers independently determined that Pteraichnus tracks could only be pterosaurian in origin (Mazin et al. 1995; Lockley et al. 1995), which turned attitudes around universally. No one else bought into the bipedal story except Bennett (1997, 2003) who illustrated the oddly proportioned and fingerless Nyctosaurus as a biped, but otherwise fell in with the quadrupedal folks.

The Bipedal Ancestor Irony
Virtually all the quadrupedal theorists also insist on a close relationship with the obligate biped, Scleromochlus and a close relationship to basal bipedal dinosaurs. Hmm…

The Heretic
My own phylogenetic work (Peters 2000, 2011) shows that basal fenestrasaurs (including pterosaurs) were occasionally to obligatorily bipedal and that several clades of derived pterosaurs were quadrupeds. All pterosaurs would have been capable of bipedal locomotion in the manner of lizards that can attain a bipedal configuration (Fig. 1, that’s how they spread their wings in preparation for a take-off). However many clades preferred quadrupedal locomotion during beachcombing/feeding/ordinary walking as demonstrated by their quadrupedal ichnites and the relative length of the fore and hind limbs. This form of locomotion was secondarily derived, as demonstrated by the orientation of the manual fingers. Manual digit 3 often is oriented posteriorly, the opposite of all other terrestrial tetrapods, and digits 4 and 5 were elevated off the substrate.

BAHH!
The quad proponents dispute virtually all suggestions of bipedality (see below). Hone and Benton (2007) went so far as to say, Cosesaurus is treated as a biped by Peters (2000) with characters coded based on this assumption.” Not sure how that could possibly affect bone traits and ratios, but that’s the attitude and paradigm out there. The authors were aware that Peters (2000) stated Cosesaurus was an occasional biped based on matching its feet to Rotodactylus ichnites, which are occasionally bipedal.

The Evidence from Ichnites
So far we have quadrupedal ichnites for pre-germanodactylids, ornithocheirids, pterodactylids, ctenochasmatids and azhdarchids. We have pedal ichnites without manus impressions for anurognathids. We have pedal ichnites with occasional manus ichnites for cosesaurids that are called Rotodactylus (Peters 2011).

A 2003 Argument Against Bipedal Pterosaurs
Darren Naish is a brilliant paleontologist with many discoveries to his credit, but on this subject he was in the “all quadruped virtually all the time” camp. In 2003, Darren discussed on the DInosaur Mailing List (DML) bipedality in lizards compared to that of pterosaurs in response to the publications of Peters (2000 and 2002) and several posts I had made to the DML. I have abridged his arguments (in yellow below, but you can read his full post here).

Darren: …here I state more clearly why I think the lizard/pterosaur analogy is flawed. then he quotes an earlier post I made to the DML , “If lizards can do it, irrespective of the math, pterosaurs could do it because they have superior equipment (increased sacral number, anteriorly hypertrophied ilium = bigger thigh muscles). As in birds or bipedal lizards, the CoG can be easily manipulated to be either head heavy or tail heavy by moving the tail, head, femur, tibia or angle of the back. Nothing out of the ordinary is required to balance a pterosaur. And the forelimbs are always within a whisker of touching the substrate to deal with momentary lapses.”

Then Darren reports, “– Why do certain lizard species run bipedally? Is it just so that they are faster? Probably not: the fastest lizards are quadrupedal runners.”

Indeed. Speed is not the reason.

Darren: “What appears most likely is that bipedal running in lizards has evolved to circumvent Carrier’s constraint: by relying on the hindlimb complex alone, bipedal running lizards are not compressing the thorax as they run, and they are therefore able to maintain breathing while sprinting (in contrast to quadrupedal running lizards).

Unfortunately not true. According to Christopher Clemente“When you see a lizard running bipedally, it’s just a consequence of its acceleration.”  Clemente found that lizards trotting on two legs ran out of steam quicker, indicating that bipedalism does not serve to conserve energy.

Bipedal lizard video marker

Figure 1. Click to play video. Just how fast can quadrupedal/bipedal lizards run? This video documents 11 meters/second in a Callisaurus at the Bruce Jayne lab.

If you want to see a video of a quadrupedal lizard screaming along at a breakneck pace, then, for reasons known only to itself, lifts up its forelimbs and continue running, click here. This is not an acceleration situation. Some lizards run more upright than this one.

Then Why Go Bipedal?
Clemente said, “If you’re not using your front legs anymore, they can develop for something else.” Pterosaur predecessors, like Cosesauruswere flapping their forelimbs according to their bird-like/ pterosaur-like, strap-like scapula and locked down stem-like coracoids (both very un-lizard-like).

Sharovipteryx, another pterosaur sister, could not have contacted the substrate with such short forelimbs and long hindlimbs. It too flapped forelimbs anchored with a stem-like coracoid.

Longisquama was similar, but with much larger, more pterosaur-like hands. Certain pterosaurs were secondarily quadrupedal, as demonstrated by phylogeny and the lack of pronation in the manus. Certain pterosaurs left only pedal impressions.

Darren: Given that pterosaurs would clearly not have needed to avoid Carrier’s constraint (because, even if they were to run quadrupedally, they would not be compressing the thorax with each stride), why run bipedally?

Bipedal lizards do not avoid Carrier’s constraint.
Following Clemente’s comments (above), bipedal lizards “run out of gas” sooner rather than later. So, they’re still holding their breath while running bipedally. In pterosaurs a short stiff torso was one trait to help avoid Carrier’s constraint. Combine that with a lack of large caudofemoral muscles. Lizards use these to propel their sprawling hind limbs with alternate lateral pulls of the femur. Instead pterosaurs and their fenestrasaur antecedents had large, dinosaur-like thighs as long as the extent of their elongated ilia. They ran using fundamentally different muscles than lizards do (thigh muscles vs. tail muscles), and basal pterosaurs had more erect hind limbs than more derived pterosaurs.

Darren: Furthermore, given that pterosaurs exhibit features associated with leaping (see, e.g., Bennett 1997) and/or scansoriality, it is probable that they wouldn’t need to sprint in order to take off.

Not sure why Darren discounts running in creatures capable of leaping. I can think of several mammals that are great leapers AND runners (rabbits, deer, roadrunners, squirrels, big cats, Michael Jordan. With birds some can take off with a simple leap. Others require a runway.

Darren: Bottom line: there is no inherent ‘need’ for good bipedal running abilities in pterosaurs, in contrast to the situation in lizards.

Unfortunately, Darren did not take into account the possibility of a secondary sexual characteristic, flapping, that pterosaur predecessors practiced (based on their stem-like coracoids). Flapping to show off is how pterosaurs developed the necessary ‘equipment’ to flap to fly. Ironically, Darren’s remarks seem to be indicating there IS a need for bipedality in lizards, after arguing there was no good reason for it in lizards either (see above) – yet they do it! (but not for sex~). Evolution does not proceed based on “need” in any case, but on random changes, some of which prove to enhance survivability.

Darren asks, “What allows certain lizards to run bipedally? Dave is fond of stating that pterosaurs could run bipedally because they exhibit an increased number of sacrals relative to their probable outgroups, and a large preacetabular process on the ilium. As has been pointed out several times in the literature, it?s relatively easy for a lizard to run bipedally IF it combines these two features WITH (1) hindlimbs that are proportionally longer than its forelimbs (and consequently the animal has proportionally short forelimbs), (2) a proportionally short thorax and (3) short neck*, and (4) a long muscular tail (see Synder 1954, 1962, Bellairs 1969, Rieppel 1989 etc). Note that most of these features are to do with reducing the mass of the foreparts and thus shifting the CoG caudally. On point (4), as shown by Russell and Bauer (1992), the most important anatomical correlate of bipedality in lizards is the presence of a large m. caudofemoralis longus that inserts relatively distally on the tail (thus explaining why the lizards that run bipedally are the same ones that don?t practise caudal autotomy). *Apparently _Chlamydosaurus_ has a longer neck than most other agamids. Its neck is still not as proportionally long as that of a pterosaur though. Pterosaurs obviously don’t have proportionally short forelimbs, but more importantly they don’t have the short neck seen in bipedal lizards, nor do they have a tail that would have supported a large m. caudofemoralis longus: even in basal long-tailed forms, transverse processes (and hence a reliance on m. caudofemoralis longus) are extremely reduced (and, incidentally, there is no indication that pterosaurs switched to the knee-based retraction system seen in birds). On the relevance of this reduction in caudofemoral musculature to bipedal locomotion, Synder (1954) writes “while a long, heavy tail does not necessarily indicate bipedal habits, a short, lighter tail precludes the possibility of this type of locomotion? (p. 9). Given then the profound differences evident here between pterosaurs and bipedal lizards, I think the analogy is seriously suspect.”

Unfortunately Darren (like so many others) completely ignores or overlooks the origin of bipedality in pterosaur ancestors that I described in 2000. Bipedality appeared with Cosesaurus, which had feet which matched occasionally bipedal and always narrow-gauge, digitigrade tracks. Cosesaurus, Longisquama and basal pterosaurs (including anurognathids) all had short necks. Longer necks evolved later. Sharovipteryx, an obvious biped, had a long neck. So that’s not an issue. Basal pterosaurs with short forelimbs and long hindlimbs, like MPUM6009 would have been awkward quadrupeds. The longer forelimbs developed AFTER pterosaur ancestors were already flapping, leaping and running about bipedally.

Darren continues, “– So what of the alleged correlates of bipedality present in pterosaurs? Dave suggests that an increased number of sacral verts and a hypertrophied preacetabular process on the ilium are indicative of “improved: bipedality in pterosaurs. The problem is that, firstly, the features discussed above are needed as well (viz, proportionally short neck, big m. caudofemoralis longus etc), and, secondly, when the sacral and iliac features are present without these others, they may not be indicative of bipedality but of quadrupedality. Look at (e.g.) ceratopsians. Relative to basal ceratopsians, ceratopsids have a longer preacetabular process and an increased number of sacrals (10-11 compared to 6), so according to your criteria ceratopsids might be better suited to bipedality than psittacosaurs. Parareptiles come to mind too: in nycteroleterids, nyctiphruretids, procolophonoids and sclerosaurs there are (usually) 3 sacrals and a short or absent preacetabular process, but in pareiasaurs – most notably in big derived forms like _Scutosaurus_ – there are 4-6 sacrals and the preacetabular process may be so hypertrophied that the pelvis looks much like that of a pterosaur (see Fig. 14E in Lee 1997). As in ceratopsians, these sacral and iliac trends are to do with improved quadrupedal abilities.”

Well, when you start comparing pterosaurs to pareiasaurs and ceratopsians, I think we can all agree, Darren is really reaching here. Certainly a high sacral number is a convergent feature here, but for different reasons. Note, he avoids mention of Sharovipteryx and Cosesaurus, both with an increased sacral count and much closer to pterosaurs than pareiasaurs and ceratopsians.

In bipeds, like pterosaurs and dinosaurs (both bipeds and descendants of bipeds), the sacrum is put under greater stress as the fulcrum balancing all the weight anterior to the sacrum and all the weight aft. Elongating the ilium, adding to the muscle mass of the thigh, along with strengthening the fulcrum is the reason for adding sacrals (often coosified) in pterosaurs. No one championing the quadrupedal configuration has ever proposed another reason for increasing the sacral count and ilium length in pterosaurs. Sure cynodonts added sacrals. The also reduced their caudofemoralis muscles and their tails while elongating their ilia, all convergent with pterosaurs – without going bipedal. Anyone can take parts and make arguments any way they want to, but they can’t take the whole suite of characters and make the same argument. And, as Darren and most paleontologists would agree, parsimony only rules when you look at the sum of a taxon’s traits, not just a few of its convergent parts.

Darren continued, “A better way of testing for bipedality in Pterosauria might be to look at intermembral indices (viz, forelimb:hindlimb ratios), at the CoG (as I mentioned, Sangster has been working on this), at unambiguous soft tissue evidence (e.g., the Crato azhdarchoid with its preserved brachiopatagium), or at trackway evidence? and right now the evidence from all of these areas shows that quadrupedality is better supported, or in other words that pterosaurs were more likely quadrupedal.

Here Darren is talking about most pterosaurs, not basal taxa or their ancestors. As above, all pterosaurs more derived than MPUM6009 were capable of placing their hands on the substrate – without bending over an iota! (a fact typically overlooked in most other quadrupedal reconstructions of pterosaurs). Even so, the most primitive pterosaurs for which we have ichnites, the anurognathids, preserve no manus impressions.

Darren asked, “– Why be bipedal anyway when the forelimbs are plenty
long enough? Dave notes that, in bipedal pterosaurs, “the forelimbs are always within a whisker of touching the substrate”. Well, if that;s so, it seems more likely to me that the animals would have employed the forelimbs in locomotion. I can’t think of a group of living animals in which the forelimbs are close to the substrate, and are not then employed in locomotion (think monkeys and apes). Again, the hard evidence we have (trackways) shows that the forelimbs were deployed in quadrupedal locomotion.

Darren was not aware of the other hard evidence of pedal impressions of pterosaurs without manus impressions.  In virtually all pterosaurs the forelimbs were plenty long enough to touch the substrate and the tracks show that many clades were quadrupedal. I never argued against that. Some pterosaurs reverted to quadrupedal locomotion, always retaining the ability to walk or run bipedally, simply by lifting the forelimbs off the substrate. Their toes were already planted beneath their centers of gravity, the shoulder glenoid, as ALL of my pterosaur reconstructions demonstrate. It’s that simple. As in Darren’s example, think lemurs, monkey and apes, all of which can go bipedal whenever they want to.

Darren concludes with, “The presence of a well-developed iliopubic ligament (=ligamentum inguinale) might indicate that pterosaurs were good at elevating the thorax, but given that everyone agrees that pterosaurs must have been bipedal when opening or closing their wings (and they thus would have needed to elevate the thorax at least occasionally), this doesn’t necessarily indicate bipedal running. Incidentally, see Hutchinson (2001, pp. 156-8) for a discussion of iliopubic ligament distribution in Reptilia. Because reptiles including ceratopsids, pareiasaurs and turtles appear to have had a hypertrophied iliopubic ligament as well, the correlation between this structure and an enhanced bipedal ability is not immediately clear.

I appreciate the half-hearted concession Darren made regarding opening the wings. Nice to hear. Yes, pterosaurs had to stand bipedally to open the wings. (Forelimb launch was not a consideration when Darren wrote this, and it has major flaws in any case.) The anterior extension of the ilium does not always signal a bipedal configuration (e.g. basal mammals). I never argued that it did. But in the case of pterosaur antecedents, a long ilium is one of a long list or suite of traits  shared with pterosaurs. In Peters (2002), I was moved to report that other than the twist of the wing finger, nearly every pterosaurian trait could be found in fenestrasaur antecedents. No has ever argued against that hypothesis and presented a more parsimonious series of antecedents from some other distant clade. And it has been ten years!

Darren further concluded, “The long forelimbs of pterosaurs, combined with the morphology of the patagia and the evidence from trackways, show that the interpretation of pterosaurs as predominantly quadrupedal is better supported and less speculative than interpretation of them as bipedal.”

Cosesaurus and Rotodactylus, a perfect match.

Figure 2. Click to enlarge. Cosesaurus and Rotodactylus, a perfect match. Elevate the proximal phalanges along with the metatarsus, bend back digit 5 and Cosesaurus (left) fits perfectly into Rotodactylus (right).

Predominate? Yes. However, Darren was not, at the time, aware of certain pterosaur pedes imprints attributed to anurognathids that were not attended by manus imprints. Those were described in Peters (2011), but “Sauria aberrante” (Casamiquela 1962) and Rotodactylus (Peabody 1948, Fig. 2) have been known for decades. Even though they are in the minority at present, they still count.

In summary, looking for reasons to go bipedal is probably not the way to go. Looking at bits and pieces by themselves is also not the way to go. Cladistic analysis and judging a taxon as a whole are the ways to go. And I like the example of quadrupedal/bipedal primates. That’s a good analogy!

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.

Darren Naish, School of Earth & Environmental Sciences University of Portsmouth UK, PO1 3QL

References
Click to read Darren Naish’s complete comment to the DML
Bennett SC 1997. Terrestrial locomotion of pterosaurs: a reconstruction based on Pteraichnus trackways. Journal of Vertebrate Paleontology, 17: 104–113.
Bennett SC 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus.Paläontologische Zeitschrift 77: 61-75.
Casamiquela RM 1962.
 
Sobre la pisada de un presunto sauria aberrante en el Liassico del Neuquen (Patagonia). Ameghiniana, 2(10): 183–186.
Lockley MG, Logue TJ, Moratalla JJ, Hunt AP, Schultz RJ and Robinson JW 1995. The fossil trackway Pteraichnus is pterosaurian, not crocodilian; implications for the global distribution of pterosaur tracks. Ichnos, 4: 7–20.
Mazin J-M, Hantzpergue P, Lafaurie G and Vignaud P 1995. Des pistes de pterosaures dans le Tithonien de Crayssac (Quercy, France). Comptes rendus de l’Academie des Sciences de Paris, 321: 417–424.
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2000.
 Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7(1): 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 2007. 
The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology 22:437-442.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos, 18: 2, 114 —141.
Stokes WL1957. Pterodactyl tracks from the Morrison Formation. Journal of Palaeontology, 31: 952–954.
Unwin DM 1997. Pterosaur tracks and the terrestrial ability of pterosaurs. Lethaia, 29: 373–386.

Darren’s References:
Bellairs, A d’A 1969. The Life of Reptiles, Vol. 1_ Weidenfeld & Nicolson (London), pp. 282.
Bennett SC 1997. The arboreal leaping theory of the origin of pterosaur flight. Historical Biology 12, 265-290.
Hutchinson JR 2001. The evolution of pelvic osteology and soft tissues on the line to extant birds (Neornithes). Zoological Journal of the Linnean Society 131, 123-168.
Lee MSY 1997. Pareiasaur phylogeny and the origin of turtles. Zoological Journal of the Linnean Society 120, 197-280.
Reeder TW, Cole CJ and Dessauer HC 2002. Phylogenetic relationships of whiptail lizards of the genus_Cnemidophorus_ (Squamata: Teiidae): a test of monophyly, reevaluation of karyotypic evolution, and review of hybrid origins. American Museum Novitates 3365, 1-61.
Rieppel O 1989. The hind limb of Macrocnemus bassanii (Nopcsa) (Reptilia, Diapsida): development and functional anatomy. Journal of Vertebrate Paleontology 9, 373-387.
Russell AP and Bauer AM 1992. The m. caudifemoralis longus and its relationship to caudal autotomy and  locomotion in lizards (Reptilia: Sauria). Journal of Zoology 227, 127-143.
Synder RC 1954. The anatomy and function of the pelvic girdle and hind limb in lizard locomotion. American Journal of Anatomy 95, 1-45.
Synder RC 1962. Adaptations for bipedal locomotion of lizards. American Zoologist 2, 191-203.