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.

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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.

Scathing Book Review – Pterosaurs (Witton 2013) – Dimorphodon problems

Updated June 10, 2015 with a revised Dimorphodon takeoff  (Fig. 3) that included a downstroke right at the start of the leap. 

Earlier we looked at the inaccurate cartoon produced of the hind-wing glider, Sharovipteryx by author and illustrator, Mark Witton.  Here we’ll continue up the phylogenetic line to consider the disfigurements Witton applied to a basal pterosaur.

As a purported pterosaur expert, Mark Witton, author of the new book “Pterosaurs,” should be able to accurately portray a pterosaur skeleton. Unfortunately his Dimorphodon drawing is filled with errors (Fig. 1). For comparison, an accurate portrayal based on a bone-by-bone tracing is shown below (Fig. 4).

Dimorphodon by Mark Witton, filled with errors.

Figure 1. Dimorphodon by Mark Witton, filled with errors. This pose does allow Witton to avoid the digitigrade and bipedal issues, which would be visibly odd if set in a standing pose. Is there any way this pterosaur could complete a pushup that would launch it into the air high enough to unfold that big wing finger before crashing to Earth. This is a risky move every time it’s attempted!

  1. Apparent mandibular fenestra – caused by a slipped surangular detailed here and confirmed by Bennett (2013).
  2. All pterosaurs have eight cervicals (prior to ninth vert with deep ribs)
  3. 1st and 2nd dorsal ribs should be hyper-robust and 2nd articulates with sternal complex
  4. Prepubis is the wrong shape and should articulate with the ventral pubis at its stem and against the edges of the last gastralia at its anterior process
  5. Caudal vertebrae should align with the sacrals with neural spines rising above the ilium
  6. The radius in all tetrapods originates on the lateral humerus, not the medial
  7. The pteroid should originates on the proximal carpal, not the preaxial carpal (Peters 2009, Kellner et al. 2012)
  8. Metacarpals 1-3 should align palmar sides down, out and away from metacarpal 4. This provides room for all four metacarpals to have extensors tendons.
  9. Following a wrong hypothesis, Witton orients his pterosaur fingers posteriorly, but all pterosaur tracks show digits 1-2 were oriented laterally and only digit 3  oriented posteriorly due to a spherical metacarpophalangeal joint, as in many lizards.
  10. Pedal digit 5 never flexes at pedal 5.1 (Fig. 1), but does flex nearly 180 degrees at pedal 5.2 in fossils (Fig. 4). Witton disfigured toe 5 this way in order to have it frame a uropatagium, as has been suggested for Sordes and MSNB 8950, but both are misinterpretations detailed here and here. The actual orientation of pedal digit 5 is detailed in Peters (2000, 2011, Fig. 4) and here and here.
  11. The tail and torso both appear to be too short. Freehanding, like Witton does, is not conducive to accuracy.

Forelimb pterosaur leaping
One of the hypothetical practices Witton endorses for pterosaurs across the board is the much promoted, but wisely criticized, forelimb launch. We’ve discussed its failing before. There is still no evidence for it in the fossil record, although Witton pins his hopes on a three-year-old rumor. Witton illustrates nearly all of his pterosaurs in the forelimb launch configuration (fig. 1). What Witton doesn’t show is what happens shortly thereafter. Here (Fig. 2) is Witton’s Dimorphodon trying to become airborne after attempting a mighty pushup with folded wings beneath its body and mighty triceps extensors working their hearts out. Forelimb leaping is also tremendously difficult for athletes as seen here. Click the image (Fig. 2) to animate it if not already animated.

Click to animate. Witton's Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, pushes the pterosaur down. There's just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap.

Figure 2. Click to animate. Witton’s Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, brings the pterosaur down. There’s just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap. Human athletes cannot get this high. At the apex of this leap the wings are just beginning to unfold. Moreover those big wing fingers have to swing through a ventral arc before swinging above the torso prior to the first wing beat. Finally, there’s not much forward thrust here.

There has always been a better way for Dimorphodon to leap (Fig. 3), like a leaping lizard and the vast majority of all tetrapods: by using the hind limbs, like birds, frogs and kangaroo rats do.

Figure 3. Click to animate. Dimorphodon hind limb leap - like a bird or a frog. There's nothing wrong with this method. It gets the wings open right away to provide thrust and lift at the apex of the hind limb portion of the leap. The thighs are massively muscled, more so than the forelimbs. The extension and flexion of the toes provide that last little umph! to the take-off, as in frogs and kangaroo rats. And let's remind ourselves, pterosaurs were fully capable of bipedalism and leaping, as shown here.

Figure 3. Click to animate. Dimorphodon hind limb leap – like a bird or a frog. There’s nothing wrong with this method. It gets the wings open right away to provide thrust and lift at the apex of the hind limb portion of the leap. The thighs are massively muscled, more so than the forelimbs. The extension and flexion of the toes provide that last little umph! to the take-off, as in frogs and kangaroo rats. And let’s remind ourselves, pterosaurs were fully capable of bipedalism and leaping, as shown here.

Exceptions include tiny vampire bats (Fig. 4) which arrived at forelimb leaping secondarily, as a bi-product of their lifestyle and the extremely weak legs of bats in general. Primates, jumping rodents and flying lemurs are much better at hind limb leaping than bats are. Click here to see the video of the top 10 fastest, highest jumping animals.

Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It's more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Figure 4. Dimorphodon and Desmodus (the vampire bat) compared in size. It’s more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Size matters!
Dimorphodon is not a large pterosaur. Even so, it is several times larger than a vampire bat (Fig. 4). Its not just the effect of gravity, which increases with the cube of height, but it’s also the cushion of air, that becomes so much more cushiony the smaller a creature gets and as it adds surface area. That’s why vampire bats can get away with forelimb leaping while pterosaurs larger than a vampire bat likely could not. And giraffe-sized pterosaurs could probably leap with their forelimbs about as high as a giraffe can leap with its forelimbs.

At least he’s consistent
Witton incorrectly pastes dorsal metacarpals 1-3 back-to-back against metacarpal 4 (now rotated palmar side posterior to enable wing folding, Fig. 1). That orients the free fingers palmside anterior during flight and all posteriorly when hyperextended during terrestrial locomotion (Fig. 1). Unfortunately that doesn’t match pterosaur handprints, which are lateral for digits 1 and 2 (sometimes anterior for digit 1) and posterior for digit 3 due to a spherical joint there. That also means when a pterosaur wants to clamber up a tree, it can’t because in Witton’s view the palms are face up, as if begging.

The better orientation is palm side down while flying (or palms medial (like clapping) when walking). That also gives all four forelimb digits plenty of room to have extensor tendons. The preferred configuration also means the fingers hyperextend laterally when walking with the exceptional digit 3 oriented backwards to match ichnites. Details here.

But not always consistent
Witton’s figure 7.10 has the palms facing each other while the pterosaur is floating. They should be palms up in his view.

Whether pterosaurs had their fingers oriented laterally or posteriorly, that’s arrived at secondarily, because no tetrapods do this plesiomorphically. Their fingers always point in the direction of travel. The secondary lateral placement of the fingers on the substrate occurred after a bipedal phase shown in Cosesaurus/Rotodactylus and emphasized in Sharovipteryx. In Witton’s hypothetical scenario, the one that ignores real fossils, pterosaurs and their ancestors were never bipeds.

Pterodactylus walk matched to tracks according to Peters

Figure x. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

No Bipedal Footprints?
Along with the adoption of the forelimb launch, Witton (2013) rejects the bipedal capabilities of pterosaurs, first promoted by Padian (1983) and later by Peters (2000a, b, 2011). Peters (2000a, b) recognized that pterosaur tracks known at that time were all plantigrade and quadrupedal but recognized that pterosaurs anatomy could vary and that even the quadrupdal pose included having the toes directly beneath the center of gravity, the shoulder glenoid (Fig. x). That enabled the forelimbs to be raised without changing elevating the back. Witton ignored this data. He also reports there are no records of digitigrade pterosaurs, but his book includes an illustration of one (his figure 7.9) and he ignores the several digitigrade pterosaurs in other published works (Peters 2011, Fig. 5) mentioned, referenced and illustrated here, here, herehere and here.

Digitigrade pterosaur tracks

Figure 5. A pterosaur pes belonging to a large anurognathid, “Dimorphodon weintraubi,” alongside three digitigrade anurognathid tracks and a graphic representation of the phalanges within the Sauria aberrante track. Digit 5 impressing far behind the other toes is the key to identifying tracks as fenestrasaurian or pterosaurian.

Not Digitigrade? It pays to be specific here.
Witton referenced Clark et al. (1998) who reported that basal pterosaurs, like Dimorphodon, had flat feet because they could not bend the metatarsophalangeal joint due to the squared-off (butt joint) shape. Peters (2000a) showed that Cosesaurus, an ancestor to pterosaurs, had the same sort of butt-joint metatarsophalangeal joints, and that its feet exactly matched Rotodactylus tracks, but only when the proximal phalanges were all elevated (because they could not be bent), in accord with the findings, but not the conclusions of Clark et al. (1998). Peters (2000a) also showed that many pterosaurs, from Dimorphodon Pteranodon, raised the metatarsals and proximal phalanges in the same way to produce a digitigrade pes. The reduction of pedal digit 5 in derived pterosaurs led to their becoming plantigrade. Beachcomber pterosaurs also rested on their ski-pole like arms and became quadrupeds, but those forelimbs did not provide thrust due to the placement of the hands in front of the shoulder sockets.

Cosesaurus foot in lateral view matches Rotodactylus tracks.

Figure y. Cosesaurus foot in lateral view matches Rotodactylus tracks.

Ironically,
while Witton favors the archosaur model for pterosaur origins, he rejects digitigrade pedes in pterosaurs, a trait widely found in basal dinosaurs and basal bipedal crocs.

Bipedal capability (in the manner of modern bipedal lizards), a narrow chord wing membrane and twin uropatagia solve all sorts of problems introduced and sustained by Mark Witton and the other experts he hangs with. And, there’s fossil evidence for all of this (throughout this blog and reptileevolution.com)! And none for the Witton follies.

Extension and Flexion Forelimb Limitations
Pterosaur arms cannot fully flex if they have large pteroids. The elbow joint also prevents this. Pterosaur arms cannot fully extend due to elbow limitations and the presence of the propatagium, which, as in birds, prevents overextension. These problems limit the ability of the forelimbs to flex and extend completely, like frog legs, to produce the best leap possible.

No Such Limitations in the Hind Limb
Simply leaping (or running and leaping) gets the job done so much better than an exaggerated pushup. Like birds, pterosaurs used their wings to flap and fly. That thrust can be employed during the initial hind limb leap, but not during the initial forelimb leap.

Leaping Lizard
If you want to have a good laugh while watching a rather ordinary lizard leap 3x its body length, check out this YouTube video. Just think how far a pterosaur could leap with those much longer frog-like hind limbs and elongated hips providing power at the femur, the tibia, the metatarsus and the toes in coordinated fashion, accentuated by powerful thrust provided by large flapping wings.

References
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Kellner AW, Costa FR, and Rodrigues T. 2012. New Evidence on the pteroid articulation and orientation in pterosaurs. Abstracts, Journal of Vertebrate Paleontology.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Peters D 2011.  A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos, 18: 2, 114 —141

New Bipedal Tapejara Take-Off Video

A bipedal pterosaur video!
Just ran across this Tapejara skeleton take-off, fly and land video from the Huffington Post – and its a bipedal takeoff! The original came from the Sankar Chatterjee lab at Texas Tech in November 2012.

Click to animate. Tapejara take-off, flight and landing by the Sankar Chatterjee lab. Red arrows point to morphology problems. 1. Bend humerus back further. 2 Bend elbow more. 3. Pteroid goes to carpals, not the finger joint, unless that's a metacarpal lacking fingers. 4. Knees should be splayed 5. Extend hind limbs laterally.

Figure 1. Click to animate. Tapejara take-off, flight and landing by the Sankar Chatterjee lab. Nice to see. So many things are right about this animation. Yet, red arrows point to minor morphology problems. 1. Bend shoulder back further. 2 Bend elbow forward more. 3. When the elbow is bent, the pteroid angles out from the radius, framing the propatagium better. 4. Metacarpal lacking free fingers. 4. Knees should be splayed 5. Extend hind limbs laterally in flight.

The Huffington headline reads: Pterosaur ‘Runways’ Enabled Huge Prehistoric Flying Animal To Get Airborne, Study Suggests. By: Douglas Main, LiveScience Contributor
Published: 11/08/2012 03:01 PM EST on LiveScience.

How did pterosaurs takeoff and fly?
According to Main, “A new computer simulation has the answer: These beasts used downward-sloping areas, at the edges of lakes and river valleys, as prehistoric runways to gather enough speed and power to take off, according to a study presented Wednesday (Nov. 7) here at the annual meeting of the Geological Society of America.’First the animal would start running on all fours,'” Texas Tech University scientist Sankar Chatterjee, a co-author of the study, told LiveScience. “Then it would shift to its back legs, unfurl its wings and begin flapping. Once it generated enough power and speed, it finally would hop and take to the air,” said Chatterjee, who along with his colleagues created a video simulation of this pterosaur taking flight.

Unfortunately Chatterjee doesn’t give pterosaurs the credit they deserver when he reports, “This would be very awkward-looking,” he said. “They’d have to run, but also need a downslope, a technique used today by hang gliders. Once in the air, though, they were magnificent gliders.” 

So, a downslope was necessary and flapping was rare, evidently, in Chatterjee’s view. Unfortunately, Chatterjee, like the other pterosaur experts, has a built-in bias regarding pterosaurs in that he sees them too weak to run to take-off speed, except downhill, and too weak to flap sufficiently to create enough thrust without a runway, and too weak to flap with vigor while gaining altitude. The caption (Fig. 1) includes a few reconstruction suggestions.

Bipedal lizard video marker

Figure 2. 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. just think what a pterosaur could attain, even without its wings.

Living bipedal lizards are anything but awkward-looking.
In fact they look incredibly like graceful bullets, faster than a rabbit  and impossible to see on film unless greatly slowed down, as shown here in the Bruce Jayne lab films.

Pterosaurs have what bats and birds have
The ability to flap and fly vigorously. Huge pectoral  and upper arm muscles, fur-covered body, independent wings and legs. Gosh, I feel like I’m looking out for the little guy (pterosaurs) here, having to defend them from pterosaur experts.

Doggone it. 
I realize everyone has their pet ideas and given those its important to trash the ideas of others. But this is Science and we can come to certain agreements. Nice to see Chatterjee showing that Tapejara could run bipedally! That’s a first step. Hopefully the round table at the Pterosaur Symposium in Rio in May will bring forth broad agreements on several issues without resorting to shoe throwing.

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.

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.

Mesadactylus and Mesadactylus? – A new anurognathid and a new flightless pterosaur!

Jensen and Padian (1989) described the bits and pieces of the Mesadactylus holotype (Fig. 1, right). The type specimen is the synsacrum, distinct in morphology with an anteriorly high and completely fused neural plate. Jensen and Padian (1989) considered Mesadactylus a basal pterodactyloid pterosaur. Bennett (2007) considered the synsacrum anurognathid even though no other anurognathid had such a sacrum.

More recently Smith, Sanders and Stadtman (2004) recovered new material from the same late Jurassic formation. They ascribed these scattered specimens to Mesadactylus despite their distinct size and other differences. Based on their scale bars, these elements are reconstructed for the first time here (Fig. 1, left). Overall they represent a much larger specimen of a different type of pterosaur. Individually there are few similarities among the bones both shared in common.

The Mesadactylus holotype and referred specimens reconstructed to match the flightless pterosaur, Sos2428.

Figure 1. Click to enlarge. The Mesadactylus holotype (Jensen and Padian 1989, right) nests with the North American anurognathids. Several referred specimens (Smith et al. 2004, left), when reconstructed, nest at the base of the azhdarchidae, with Huanhepterus and the flightless pterosaur SOS 2428. The pink cervicals are duplicated from the single gray one. It is fairly clear, these two restored taxa are not congeneric.

Phylogenetic Analysis
Both specimens were entered into the large pterosaur tree. The holotype Mesadactylus nested with the other North American anurognathid, Dimorphodon? weintraubi and the early Cretaceous IVPP embryo.

I like to give others credit where credit is due and Bennett (2007) got this one right!

The referred specimen nested away from the anurognathidae, at the base of the azhdarchidae, along with the flightless pterosaur, SoS 2428 (Fig. 2) and its kin, BSPG 1911 I 31 (no. 42 in the Wellnhofer 1970 catalog), alongside Huanhepterus.

Referred Bones
Only one cervical vertebrae of the referred specimen was illustrated, so here (Fig. 1) it was duplicated and shortened, producing an elongated restored neck.

That relatively large rib (no doubt the second dorsal) indicates a voluminous torso. Proportionately this rib is much larger than the second dorsal rib in SoS 2428. So either the rib does not belong with the other referred bones or the torso was relatively much larger.

The humerus includes a very large shoulder articulation and a small deltopectoral crest, wider than deep. Manual 4.1 appears to include a fused extensor tendon process and a very short portion of m4.2 with converging margins indicating a short length.

The femur is elongated and S-curved, as in SoS 2428. All pterosaurs have a tibia of greater length, so that gives this restored specimen a stork-like or azhdarchid-like appearance.

Sos 2428. The flightless pterosaur.

Figure 2. Sos 2428. The flightless pterosaur for comparison.

Comparisons to SoS 2428 from the Solnhofen
The humerus has a distinct shape in the Colorado specimen, with a semicircular deltopectoral crest and a larger shoulder joint. As mentioned earlier, the rib is much larger in the Colorado specimen. Otherwise most of the elements are comparable.

Flightless
These clues and the phylogenetic nesting of the referred specimen suggest a close relationship with the flightless pterosaurSoS 2428. So that makes our second or third (depending on how we count SoS 2179, known only from a skull) flightless pterosaur.

Knowing what to look for now,
I wonder if there is more diagnostic material in the matrix?

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
Bennett S C 2007. Reassessment of Utahdactylus from the Jurassic Morrison Formation of Utah. Journal of Vertebrate Paleontology 27(1): 257–260.
Jenson J and Padian K 1989. Small pterosaurs and dinosaurs from the Uncompaghre fauna (Brushy Basin Member, Morrison Formation: ?Tithonian), Late Jurassic, western Colorado. Journal of Paleontology 63:364-373.
Smith DK, Sanders RK and Stadtman KL 2004. New material of Mesadactylus ornithosphyos, a primitive pterodactyloid pterosaur from the upper Jurassic of Colorado. Journal of Vertebrate Paleontology 24(4):850-856.

wiki/Mesadactylus