First African pterosaur trackway (manus only)

FIgure 1. From Masrour et al. 2017, manus only pterosaur tracks. They are BIG!

FIgure 1. From Masrour et al. 2017, manus only pterosaur tracks. They are BIG! Again I will note, only lepidosaurs can bend their lateral metacarpophalangeal joints within the palmar plane at right angles to the others, producing posteriorly oriented manual digit 3.

Masour et al. 2017
bring us new manus only Late Cretaceous azhdarchid tracks. They report, “The site contains only manus tracks, which can be explained as a result of erosion of pes prints.” They assume that the pterosaur fingers pressed deeper, carrying more weight on the forelimbs. Of course, this is a bogus explanation. No tetrapods do this. Pterosaurs put LESS weight on their tiny fragile fingers. They used their hands like skiers used ski poles.

FIgure 2. From Masrour et al. 2017, model of the trackmaker of the manus only tracks.

FIgure 2. From Masrour et al. 2017, model of the trackmaker of the manus only tracks erroneously attributed to Bennett 1997, who drew Pterodactylus, not this generalized azhdarchid.

There is another explanation for manus only tracks
called floating and poling, but that hypothesis was dismissed by the authors.

Masrour et al. dismiss the possibility of floating
by referencing Hone and Henderston 2014 in which simulations of the buoyancy of poorly constructed pterosaurs made using computers indicate that these reptiles had no ability to float well in water. This hypothesis was dismantled earlier here. In addition, Hone’s track record is not good. Neither is Henderson’s, who does not seem to care about using accurate skeletal reconstructions.

More importantly,
if Hone and Henderson put forth an anti-floating hypothesis no one (and certainly no scientist) should simply believe in it. This is Science. Others, like Masrour et al., should TEST hypotheses for validity, as was done here. Instead Masrour et al. put forth a hypothesis in which pes tracks were selectively erased over time, which seems preposterous and unnatural. This sort of selective erasure has never been observed in Nature.

Figure 1. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks.

Figure 3. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks. Remember the skull is as light as a paper sculpture.

Scientists fail
when they blindly follow bad hypotheses, just because they are published. Nodding journalists repeat what they read, whether right or wrong. Scientists test whenever they can.

Figure 5. Tapejara poling while floating, producing manus-only tracks, all to scale.

Figure 4. Tapejara poling while floating, producing manus-only tracks, all to scale. Remember the skull is as light as a paper sculpture.

Don’t believe in Henderson cartoons
(Fig. 5). Test with accurate representatives of skeletons IFig. 4).

Computational models of two pterosaurs from Hone and Henderson 2013. Note how both have trouble keeping their nose out of the water. Henderson's models have shown their limitations in earlier papers.

Figure 5. Computational models of two pterosaurs from Hone and Henderson 2013/2014. Note how both have trouble keeping their nose out of the water. Henderson’s models have shown their limitations in earlier papers.

When you don’t use cartoons for data
then you have a much better chance of figuring out how Nature did things.

Figure 4. Two configurations for Rhamphorhynchus. Because the wings act like pontoons, the torso and skull can be rotated relative to the wings to adopt a variety of floating configurations. Also note the large webbed feet, preserved in the darkling specimen. The tail can be elevated at its base.

Figure 6. Two configurations for Rhamphorhynchus. Because the wings act like pontoons, the torso and skull can be rotated relative to the wings to adopt a variety of floating configurations. Also note the large webbed feet, preserved in the darkling specimen. The tail can be elevated at its base.


Thank you for your continuing interest.
After over 2000 blog posts the origin of bats continues to be the number one blog post visited week after week, with totals equalling the sum of the next five topics of interest. That’s where the curiosity of the public is right now.

References
Hone DWE, Henderson DM 2014. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 394:89–98.
Masrour M et al. (4 other authors) 2017. 
Anza palaeoichnological site. Late Cretaceous. Morocco. Part I. The first African pterosaur trackway (manus only). Journal of African Earth Sciences (in press) 1–10.

 

https://pterosaurheresies.wordpress.com/2013/12/06/pterosaurs-were-unlikely-floaters-hone-and-henderson-2013/

Earliest Cretaceous pterosaur tracks from Spain

Pascual-Arribas  and Hernández-Medrano 2016
describe new pterosaur ichnites from La Muela, near Soria, Spain.

From the abstract
“Pterosaurs tracks in the Cameros basin are plentiful and assorted. This fact has allowed to define several Pteraichnus ichnospecies and moreover to distinguish other morphotypes. The study of the new tracksite of La Muela (Soria, Spain) describes Pteraichnus cf. stokesi ichnites that is an unknown ichnospecies until now and that confirms the wide diversity of this type of tracks in the Cameros Basin. Their characteristics correspond to the ones of the Upper Jurassic track sites of United States. Similar tracks have already been described in other tracksites, both inside and outside the Iberian Peninsula during the Upper Jurassic-Lower Cretaceous transit. Because of their shape and morphometrical characteristics they can be related to the pterosaurs of the Archaeopterodactyloidea clade. The analysis of this ichnogenus indicates the need for a deep review because encompasses ichnites with a big variety of shapes and morphometric characteristics.”

Figure 1. La Muela pterosaur manus and pes tracks, plus tracing and sister ichnotaxa among basalmost ctenochasmatids.

Figure 1. La Muela pterosaur manus and pes tracks, plus tracing and sister ichnotaxa among basalmost ctenochasmatids. Note the extreme length of manus digit 1. This may result from secondary and further impressions during locomotion. Such an extension is no typical. Ctenochasmatids have shorter fingers and claws.

By adding the traits of the La Muela track
to the large pterosaur tree (LPT, 233 taxa) it nested precisely between stem ctenochasmatids and basalmost ctenochasmatids.

Why guess when a large database already exists?
That’s why I published the pterosaur pes catalog with Ichnos in 2011.

Those manus tracks are rather typical for pterosaurs.
Impossible for archosaurs. Typical for lepidosaurs, which have looser metacarpophalanageal joints.

Pascual-Arribas and Hernandez-Medrano
draw triangles, Y-shapes and rectangles around Ctenochasma, azhdarchid and Pterodaustro tracks. Since the triangle and rectangle taxa are sisters, this nearly arbitrary geometrical description is of little phylogenetic use. Ctenochasmatids can spread and contrast their metatarsals, so they can change their pes from one ‘shape’ to another.

A second paper on Spanish ptero tracks
by Hernández-Medrano et al. 2017 describe more tracks. In the first paper, some pterosaur pedes were correctly attributed to Peters 2011. The same illustrations in the second paper were attributed to the authors of the first paper. :  )

References
Hernández-Medrano N, Pascual-Arribas C and Perez-Lorente F 2017. First pterosaur footprints from the Tera Group (Tithonian–Berriasian) Cameros Basin, Spain. Journal of Iberian Geology DOI 10.1007/s41513-017-0020-8. (in English)
Pascual-Arribas C and Hernández-Medrano N 2016. Huellas de Pteraichnus en La Muela (Soria, España): consideraciones sobre el icnogénero y sobre la diversidad de huellas de pterosaurios en la Cuenca de Cameros. (Pteraichnus tracks in La Muela (Soria, Spain): considerations on the ichnogenus and diversity of pterosaur tracks in the Cameros Basin.) Revisita de la Sociedad Geologica de España 29(2):89–105. (in Spanish)
Peters D 2011. A catalog of pterosaur pedes for trackmaker identification. Ichnos, 18: 114–141.

 

Bat wing ‘pose’ in pterosaurs? – SVP abstracts 2016

Manafzadeh and Padian 2016
attempt to provide insights into pterosaur abilities by comparing certain skeletal elements with those of a chicken, then a bat.

From the Manafzadeh and Padian 2016 abstract (abridged)
“Hip mobility is determined in part by the osteological morphology of the acetabulum and femoral head. However, the joint capsule and its ligaments constrain motion to a smaller range than what seems possible from dry bones alone. Paleontologists have tried to reconstruct the locomotion of extinct ornithodirans (1) (bird-line archosaurs) without accounting for ligamentous constraints in the hips of their extant avian relatives. We dissected the hip joint capsules of 30 free-range farmed specimens of the domestic chicken (Gallus galls) (2). For each specimen, maximum hip ranges of motion in the sagittal, frontal, and transverse planes were first determined from manipulation of carcasses. These values were then compared to ranges of motion obtained from manipulating the femora and pelvic bones alone. In the light of archosaur soft tissue homologies, these data suggest that many inferences drawn from dry bones alone have overestimated ranges of hip motion and have proposed stances and gaits for ornithodirans that would have been made implausible or impossible by soft tissues. Specifically, our findings suggest that ligamentous constraints would have prevented batlike incorporation of the pterosaur hindlimb into a uropatagium. (3) These data suggest that the “4-wing gliding” model of basal maniraptoran flight (e.g., Microraptor) would have been difficult or impossible if it required bringing the hindlimbs into a strictly horizontal plane.” (4)

Notes

  1. Everyone should know by now, pterosaurs are not stem birds. This has been known for 16 years (Peters 2000). They are stem squamates in the LRT. This has been known for 5 years, since the origin of ReptileEvolution.com and for 11 years if you read abstracts from Flugsaurier meetings (Peters 2007).
  2. Thus, using a chicken (Gallus) is inappropriate. Among living taxa, the use of the squamate Chlamydosaurus would have been phylogenetically much closer to pteros. Even then, a stretch.
  3. The bat-wing pterosaur argument has never been supported by evidence. And the uropatagium myth has also never found any evidence. It is founded on one misinterpreted specimen. Funny that the uropatagium is not found in chickens and makes its one and only appearance in the abstract here at the conclusion. Did pterosaurs have a bat-like wing [deep chord]? Or did they adopt a bat-like pose [upside down]? The abstract headline needs to clarify which is correct.
  4. The inability of theropods to abduct the femur into the parasagittal plane was shown in a Nova PBS special. Details and links here.
  5. If you want to see the range of poses in pterosaurs, click here to start. The angle of the femoral head to the shaft varies widely within the Pterosauria, from dino-like in Dimorphodon, to more splayed in higher taxa like Pteranodon (Fig. 1), Anhanguera and Quetzalcoatlus.
  6. Working with reinflated pterosaur bone replicas (Fig. 1) shows the femoral head, though able to rotate on its axis and wobble about its axis, need not move much in order to supply all necessary movement to the hind limb in flight or walking. The same holds true working with uncrushed bones. Reconstructions are SO important and so typically ignored.
Standing Pteranodon

Figure 1. Standing Pteranodon Remember, the wing membranes fold up to near invisibility in all known fossils that preserve a folded wing as the membrane is stretched between wingtip and elbow with a small fuselage fillet to mid thigh from the elbow.

References
Manafzadeh AR and Padian K 2016. Could pterosaurs adopt a batlike wing pose? Implications of a functional analysis of the avian hip ligaments for the evolution of ornithodiran stance and gait. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

Azdarchid pterosaurs as terrestrial stalkers? (Again?)

Witton and Naish 2015
once again conclude that terrestrial foraging remains the most parsimonious habit for azhdarchid pterosaurs. (Didn’t we see this earlier in Witton and Naish 2008?) There’s nothing new here. The two professors have put forth the same lame hypothesis seven years later with no apologies for the former and no improvements in the latter.

Unfortunately for Witton and Naish
the best modern analogs, birds that most closely resemble azhdarchid pterosaurs, are all shallow water waders (Fig. 3). That fact/observation has not changed in seven years. To make matters worse, and for reasons known only to themselves, Witton and Naish have set up a straw dog, the pelican for their foil.

Straw dog = In business, something (an idea, or plan, usually) set up to be knocked down. It’s the dangerous philosophy of presenting one mediocre idea, so that the listener will make the choice of the better idea which follows.

Foil = a character who contrasts with another character (usually the protagonist) in order to highlight particular qualities of the other character.

No one thinks azhdarchids resemble pelicans!
What were Witton and Naish thinking?? The key word ‘pelican” is found thirty times in their paper prior to the references. The word “stork” is found nine times. The word ‘hornbill” is found three times. The word “heron” is not found.

Figure 1. Witton and Naish 2015 azhdarchid based on a chimaera of pterosaurs including Zhejiangopterus juvenile for the skull.

Figure 1. Witton and Naish 2015 azhdarchid based on a chimaera of pterosaurs including using a Zhejiangopterus juvenile for the skull. Juvenile skulls are fine because pterosaurs develop isometrically according to ReptileEvolution.com. But Witton and Naish don’t see it that way. They think juvenile pterosaurs have large eyes and a short rostrum, like archosaurs. So, are they straddling the fence? Being hypocritical? Or taking their first steps out of the dark side?

There is no denying
that long-legged, long-necked, long-billed azhdarchid pterosaurs (Figs. 1, 2) most closely resemble today’s similarly built wading storks and herons (Fig. 3). And yet Witton and Naish don’t quite see it that way. Yes, they report that azhdarchid traits were “stork-like.” But, oddly they choose the one stork that does not have an elongate neck, the Marabous stork (Fig. 4, which often wades). SO… they also add in the ground hornbill, which does not wade because it does not have extra-long legs nor an extra-long neck.

Earlier (in 2013) we noted that hornbills most closely resemble similarly short-legged germanodactylids…something that was overlooked by Witton and Naish in 2008 and ignored in 2015.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 2. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Once again we trot out
the Zhejiangopterus azhdarchid ontogeny series (Fig. 2) demonstrating isometric growth, but Witton and Naish don’t subscribed to isometry, but rather to allometry. Perhaps hypocritically, and without comment, Witton and Naish used the giant skull of a small juvenile Zhejiangopterus and placed it on the body of an adult specimen. Why didn’t they elongate the rostrum and reduce the orbit to follow their “pterosaurs as archosaurs” hypothesis? They should have, but they didn’t. Actually, I’m glad they did not elongate the rostrum of the juvenile when they put it on the adult body. Apparently Witton and Naish hopped the fence and embraced the hypothesis that was otherwise only found at ReptileEvoluton.com and hoped to that nobody would notice.

As Pterosaur Heresies readers all know…
Pterosaurs, like other lepidosaurs, develop isometrically. Archosaurs go through a short nose “cute” phase known as allometry. You’ll see such short-nosed juvenile pterosaurs throughout the illustrations of Witton, but this is no paradigm shift for him.

The bird genera
that Witton and Naish consider effective analogues for ground-feeding azhdarchids, are the large African stork, Leptoptilos and the ground hornbill, Bucorvus (Fig. 4). I can’t imagine that anyone else agrees, especially when you have better analogs in the saddle-bill stork (Fig. 3), all ready to Google under the keyword, “stork.”

Figure 3. In my opinion this saddle-bill stork wading in water appears to be the bird closest to azhdarchid morphology and, for that matter, niche.

Figure 3. In my opinion this saddle-bill stork wading in water appears to be the bird closest to azhdarchid morphology and, for that matter, niche.

Oddly
Witton and Naish avoid the herons completely. Sure they have a smaller skull, but herons do have a long neck lacking in the birds that Witton and Naish prefer. You just don’t get both huge skull and a long neck in modern birds, otherwise we would note them as modern analogs. Wading azhdarchids were illustrated here in prior blogs.

Figure 4. Two herons, a Marabou stork and a ground hornbill, which is of these birds, the least like an azdarchid. Perhaps that is why one was not pictured in Witton and Naish 2015, despite the manuscript.

Figure 4. Two herons, a Marabou stork and a ground hornbill, which is of these birds, the least like an azdarchid. Perhaps that is why one was not pictured in Witton and Naish 2015, despite the manuscript.

Unfortunately
Witton and Naish still do not indicate the slightest interest in azhdarchid origins (Fig 5). The large pterosaur tree demonstrates their origins in tiny taxa of similar shape. That long neck developed early in their tiny ancestry and was maintained throughout.

Azhdarchids and Obama

Figure 5. Click to enlarge. Here’s the 6 foot 1 inch President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our President. This image replaces an earlier one in which a smaller specimen of Zhejiangopterus was used.

 

Heron damage from spearing a fish

Figure x. Heron damage from spearing a fish. Perhaps this was the preferred technique for the sharp billed germanodactylids, including the nyctosaurs and pterandontids.

A Weapon? Sure!
Witton and Naish describe the use of the long sharp rostrum as a weapon capable of inflicting deep wounds. We looked at that earlier with a photo of a fish after a heron stab.

When you read about Witton and Naish
disrespecting ReptileEvolution.com, remember that they wrote and published two identical papers that overlooked the obvious. They set up a straw dog where one was neither needed nor warranted. They created a chimaera reconstruction. And finally, after blackwashing my work at ReptileEvolution.com, they embraced the use of a juvenile skull on an adult pterosaur.

Perhaps there is still hope
for those two professors! Wonder how they’ll try to backpedal this?

References
Witton MP and Naish D 2008. A Reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271
Witton MP and Naish D 2015. Azhdarchid pterosaurs: water-trawling pelican mimics
or “terrestrial stalkers”? Acta Palaeontologica Polonica 60 (3): 651–660.

Stalking or wading azhdarchids (part 3)

Witton and Naish (2013) proposed a terrestrial stalking mode of operation for azhdarchid pterosaurs (Fig. 1). We looked at various aspects of that earlier here and here. Today, a few more details need to be considered.

Figure 1. Click to enlarge. On right from Witton and Naish 2013. On left reconstruction from Cai and Wei 1994 of Zhejiangopterus.

Figure 1. Click to enlarge. On right from Witton and Naish 2013. On left reconstruction based on data from Cai and Wei 1994 of Zhejiangopterus. Compare right stalking image with figure 3 wading image. Consider the great weight of that big skull on the end of that long skinny neck supported by those tiny fingers. All those problems are solved when wading (Fig. 3).

The following notes are retrieved from the boxed captions surrounding the Witton and Naish image (Fig. 1), which you can enlarge to read. 1. Reclined occipital face – Head perpetually angled towards ground when neck is lowered. – True of all wading pterosaurs and most pterosaurs in general. 2. Neck anatomy and arthrology – Long neck reduces effort to produce large movements; range of motion allows easy access to the ground. – True of all wading pterosaurs and most pterosaurs in general. 3. Skull shape and hypertrophied jaw tips – Skull morphology most similar to terrestrial feeding generalists, such as ground hornbills and modern storks; jaw elongation reduces neck action required to reach ground level – True of all wading pterosaurs and most pterosaurs in general.

Figure 3b. Zhejiangopterus fingers. Witton and Naish want you to believe that these three fragile fingers on three spaghetti-thin metacarpals are suitable weight-bearing bones - OR that mc4 is a weight-bearing bone. Neither is true. Metacarpal 4 NEVER makes an impression. The wing finger NEVER makes an impression. They were both held above the substrate in ALL pterosaurs.

Figure 2. Zhejiangopterus fingers. On left based on Cai and Wei 1994. On the right, according to Witton and Naish who want you to believe that these three fragile fingers on three spaghetti-thin metacarpals are suitable weight-bearing bones – OR that mc4 is a weight-bearing bone. Neither is true. Metacarpal 4 NEVER makes an impression. The wing finger NEVER makes an impression. They were both held above the substrate in ALL pterosaurs. The Witton Naish metacarpal is over rotated in order to allow fingers 1-3 to hyper-extend laterally, but that means the wing finger also opens laterally, not in the plane of the wing! Their mc 1-3 are pasted against mc 4, dorsal sides to dorsal side following the false Bennett model. Their fingers don’t match ichnites.

4a. Large coracoid flanges: distally displaced crests. Enlarged anchorage and increased lever arm for flight muscle; powerful takeoff ability. – Actually azhdarchids have relatively small pectoral complexes and small humeri. Witton and Naish employed a juvenile sample for their humerus. 4b. Enlarged medial wing length, decreased wing finger length. Increased forelimb stride; enlarged medial wing region and greatest lift; reduced risk of snagging wingtips on vegetation. – This is also true of all wading bottom feeders, and most pterodactyloid-grade pterosaurs in general. Also note that these traits are present in tiny Solnhofen pterosaurs (Fig. 3). Decreased wing finger length reaches a nadir in JME SOS 2482, a flightless pterosaur with a big belly and definitely NOT a stalker of terrestrial vertebrates.  5. Robust digit bones. Adaptations to weight bearing. – Obviously not true. The free fingers of Zhejiangopterus are both small and gracile and have no obvious adaptation to weight bearing. So, why are they bearing nearly all the weight of Zhejiangopterus (Fig. 1) in the Witton and Naish reconstruction? Instead, think of pterosaur forelimbs like ski poles, good for steadying (Fig. 3), especially while feeding in moving waters (Fig. 4. All weight bearing runs through the hind limb. Here is a Zhejiangopterus matched to tracks (Fig. 3). Witton and Naish make no effort to match a manus and pes to the tracks they use. 

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 3. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

6. Elongate femur (>1.6 humeral length). Increases stride efficiency; decreases attitude of axial column during feeding. In azhdarchids the femora is not relatively longer than in precursor taxa. The humerus is relatively shorter than in most pterosaurs and shorter than azhdarchid precursors like n42 in particular (Fig. 4). The torso is also relatively shorter, but this is also true of tiny precursor azhdarchids, like n42.  l7. Narrow-gauge trackways (Haenamichnus). Sub-vertical limbs providing efficient carriage when walking. – The Witton and Naish drawing overlooks the shallow angle of the femoral head relative to the shaft that would have produced a relatively sprawling, lizard-like femoral angle, as preserved in situ. Even so, the ankles would have remained below the body so long as the knees were below the acetabulum. It is also clear that pterosaur knees were bent during terrestrial locomotion, as in virtually all tetrapods.  8. Compact, padded pes and manus. Maximizes outleaver forces during step cycle; cushioning and increased traction on firm ground. – Witton and Naish based this claim on such loose and sloppy ichnites that individual toes were not distinct. Pads are also not distinct other than in the original drawing. When you look at the actual pes of Zhejiangopterus (Fig. 1) the metatarsus is indeed compact, narrower than in all other pterosaurs. 

Quetzalcoatlus scraping bottom while standing in shallow water.

Figure 4. Quetzalcoatlus scraping bottom while standing in shallow water. Note the attempt here to shift weight posteriorly while the neck is extended anteriorly. Keeping the wing finger close to the forelimb reduces the exposed wing area, important for underwater stability. The air-filled skull is weightless when in water. Not so when terrestrial stalking.

If, on the other hand, azhdarchids were waders, as were their tiny ancestors, like n42 (Fig. 5), then we can see not only their original tall, thin, morphology and their gradual evolution to great size while maintaining their wading niche (Fig. 5), but also a reason for getting bigger; gradually deeper water access. Unfortunately, Witton and Naish make no attempt to nest azhdarchids phylogenetically and certainly make no reference to their tiny ancestors.

Sisters to Microtuban

Figure 5. Sisters to Microtuban include No. 42 (more primitive) and Jidapterus (more derived).

The actual trackmaker of Haenamichnus had fingers (digits 1-3) as long as its foot. That is not found in Zhejiangopterus, but is found in Jidapterus (Fig. 5), a precursor azhdarchid.

Azhdarchids and Obama

Figure 6. Click to enlarge. Here’s the 6 foot 1 inch President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our President. This image replaces an earlier one in which a smaller specimen of Zhejiangopterus was used.

We already have pterosaurs that could have been terrestrial stalkers, like ground hornbills. We call them germanodactylids (Fig. 7). And THEY have horny/bony crests and a sharp, dangerous beak like a hornbill!

Germanodactylus and the Dsungaripteridae

Figure 7. Germanodactylus and the Dsungaripteridae. Click to enlarge. If any pterosaurs were like ground hornbills, these even had horn bills!

The beak tip of azhdarchids is a better pick-up tweezers than a stabbing knife. Better for picking up defenseless invertebrates than for stabbing terrestrial prey capable of fighting back or running away. Remember, when you go back further in azhdarchid phylogeny, you come to dorygnathids, a clade that also gave rise to wading ctenochasmatids. The devil is in the details Witton and Naish give us a pterosaur metacarpus with the false Bennett configuration (Fig. 8) in which metacarpals 1-3 are rotated as a set, like a closed draw bridge, against the anterior (formerly dorsal) surface of mc 4. That provides no space for all four extensor tendons. Now to get those fingers to hyper-extend laterally, Witton and Naish over rotate mc4 by another 90 degrees (Fig. 2). But now their wing opens laterally, no longer in the plane of the wing, as all fossils indicate.

Pterosaur finger orientation in lateral view

Figure 8. Pterosaur finger orientation in lateral view, the two hypotheses. On the left the Bennett hypothesis. On the right the Peters model that is supported by all fossil pterosaurs. These images graphically show how gracile metacarpals 1-3 were and why they could not support the weight of the pterosaur during terrestrial locomotion. The Bennett migration of the metacarpals is another problem. Witton and Naish take the Bennett mc4 one step further by rotating it another 90 degrees in order to produce lateral finger impressions. during hyperextension.

Witton and Naish give us a metacarpus and wing finger that should impress the substrate, but no pterosaur ichnite ever shows an impression of mc4 or the wing finger. So we know those two elements were held aloft during terrestrial locomotion, no matter how much Witton and Naish (and others see figure 9) wish otherwise. Witton and Naish give us a pteroid (Fig. 2) articulated to the preaxial carpal (another Bennett mistake) when the pteroid actually articulates with the radiale. Only soft tissue connects the pteroid and preaxial carpal. Witton and Naish give us pterosaur free fingers that don’t match tracks and don’t match bones. Witton and Naish illustrated from their imagination, both in shape and orientation. Witton and Naish currently hold court on pterosaur morphology, but I think you’ll agree they do so with false reconstructions. These two need to adopt strict and precise standards in which the bones agree with the ichnites and vice versa. Witton and Naish support the forelimb launch in all pterosaurs including giant Quetzalcoatlus. Considering the strain that would run through the three tiny fingers and three slender metacarpals, why do so many smart people take this idea seriously? Earlier we noted the morphological falsehoods artists added to the hand of an anhangueird pterosaur (Fig. 9) to make their forelimb launch hypothesis more logical and appealing by reducing the three free fingers and hoping the giant mc4 and wing finger made an impression in the substrate — but they don’t.

Errors in the Habib/Molnar reconstruction of the pterosaur manus

Figure 9. Errors in the Habib/Molnar reconstruction of the pterosaur manus. This manus uses the false Bennett reconstruction adopted by Witton and Naish and shortens the fingers. Corrections are provided in the lower images.

BTW I’m not blackwashing ALL of the output of Witton and Naish, just the above dozen or so problems. References Witton M and Naish D 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”? Acta Palaeontologica Polonica. available online 28 Oct 2013 doi:http://dx.doi.org/10.4202/app.00005.2013

When pterosaur workers dismiss

Earlier we looked at a new PeerJ paper by Mark Witton (2015) on the possibility of inept terrestrial pterosaurs:

Witton MP 2015.Were early pterosaurs inept terrestrial locomotors? PeerJ 3:e1018<doi: https://dx.doi.org/10.7717/peerj.1018

Witton chose (as you’ll see below by this own admission) to ignore any data on bipedal pterosaurs by Peters and others. The ignored data makes pterosaurs as agile as living birds on land. I pointed that out to him through the appropriate forum, which is the whole point of PeerJ feedback. Here’s how it went back and forth. Check out the blue links wherever possible. And don’t forget to read to the concluding paragraph after the last list of references this time.

This was my first list of suggestions, along with a required headline:

Why was published literature by Peters ignored when it addresses so many of the issues raised and dismissed by the Witton manuscript?

Several papers and a website by Peters (see below) address several problems ignored by this manuscript/paper including:

  1. Basal pterosaur ichnites (they are known, have been published and none are quadrupedal, some are digitigrade)
  2. The origin of pterosaurs (among bipedal fenestrasaurs each with uropatagia, trailing each hind limb). Objections to this scenario by Hone and Benton (2007, 2008) were due to typos in their dataset and deletion of two fenestrasaurs and 75% of the data from a third along with deletion of all data from Peters 2000, an original candidate facing the alternate scenario, among many other problems).
  3. The presence or absence of compressed metatarsals on pterosaurs, (typical keys to digitgrady and plantigrady).
  4. The uropatagium problem. (So far observed only in one specimen, Sordes, which was shown to be an illusion caused by bone and membrane dislocation during taphonomy. All other pterosaurs and their predecessors have twin uropatagia).

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

Response from the author (Mark P. Witton)
The assertion that the work of Peters has been ignored by this paper implies poor scholarship on my behalf, and that the works listed in Peters’ comment are as worthy of discussion as any other piece of pterosaur literature. It is true that Peters’ body of work did not inform my article, but my reasons for overlooking his papers will be familiar to those who follow pterosaur research.

My goal here is not to engage or argue with Peters. I – and my colleagues – have learned this is a largely futile exercise. Nor do I intend to write additional comments on this point or respond to his inevitable replies. However, for the benefit of naive parties reading these comments, some context may be useful. Because the substantial, fundamental problems with Peters’ research – the cause for myself and other workers ignoring his past contributions – are so well known to those studying fossil reptiles, I need only summarise them here. More detailed overviews of Peters’ work, the miseducation now synonymous with his name, and his attitude to other researchers, are provided by Bennett (2005) and Naish (2012) – links to these pieces are provided below.

The works of David Peters, including those related to subjects he mentions above (claims of non-pterodactyloid trackways, interpretation of pterosaur wing shapes, phylogenetic conclusions and limb function) are beyond controversial: they have been demonstrated as unreliable and untrustworthy by multiple authors (e.g. Unwin and Bakhurina 1995; Bennett 2005; Hone et al. 2009; Elgin et al. 2011). Infamously, at the core of all Peters’ work are tracings of photographs of fossil specimens, which he obtains using books, papers and online image searches. He claims to find specimen details in these photographs which no-one else has seen, including large portions of skeletons invisible to the naked eye; enormous, but invisible sheets of soft-tissue; and minute details – individual bones and fenestrae – in poorly-preserved, crushed regions of 2D fossils. These interpretations inform all his palaeobiological hypotheses, including his numerous alternative takes on extinct animal anatomy and functionality, as well as his entirely idiosyncratic concept of amniote phylogeny, which bears little resemblance to those based on standard molecular or morphological approaches.

Finding the structures Peters’ purports to uncover via his computer screen proves impossible when looking at actual specimens, even using detailed examination techniques such as CT scanning or microscopy (e.g. Unwin and Bakhurina 1995; Bennett 2005; Elgin et al. 2011). It is widely agreed by specialists that he is ascribing significance to artefacts of preservation and preparation, shadows in photographs, and other phenomena unrelated to actual specimen morphology (e.g. Unwin and Bakhurina 1995; Bennett 2005; Elgin et al. 2011; Naish 2012). Those workers who have conducted dedicated investigations of Peters’ methods provide wholly damning assessments of his ideas and techniques. On Peters’ ‘hinge-lines’ method of identifying track makers and foot function, Hone et al. (2009) “strongly advise against the use of hinge lines as a guide to functional analysis, a source of phylogenetic information, or a basis for identifying trackmakers in the ichnological record”. On digitally tracing photographs to find ‘missing’ fossil anatomies, Bennett (2005) has said “Peters’ method is flawed and his reconstructions are fantasy”. The same technique prompted Elgin et al. (2011) to describe his methods as “subjective and produc[ing] false and often fantastical images that have no value to science in general”. As early as 1995, Unwin and Bakhurina were calling his methods “unreliable”.

First-hand experience with many specimens Peters’ claims to have reinterpreted has led to my complete agreement with those denouncing his work in print: it is obvious that his papers and online articles are informed by pareidolia and personal opinion instead of an objective, scientific approach. I am aware of no practising researchers who argue differently.

Here and elsewhere, Peters argues his work is being ignored, and that workers like myself are taking ‘blinkered’ approaches to avoiding his controversial ideas. His persistent negative appraisals of virtually all findings in reptile palaeontology are now as well known as his tracing-based interpretations. Alas, one individual stating they are ‘right’ and that all other practising vertebrate palaeontologists are ‘wrong’ (as he regularly professes at his blog and website) does not make for controversy, nor does their insistence of scientific validity refute the considerable discussion showing their work as critically, fundamentally flawed (see Naish 2012 for the history, references and links surrounding Peters’ work). It seems the only individual bemoaning the lack of David Peters citations in contemporary pterosaur research is David Peters: others, including myself, see little to no benefit in the continued discussion of his unscientific, flawed approaches.

References
Bennett, S. C. 2005. Pterosaur science or pterosaur fantasy? Prehistoric Times, 70, 21-23. (direct link: http://bigcat.fhsu.edu/biology/cbennett/Bennett-PT-article.pdf)
Elgin, R. A., Hone, D. W., & Frey, E. (2011). The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica, 56, 99-111.
Hone, D. W., Sullivan, C., & Bennett, S. C. (2009). Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions. Historical Biology, 21, 67-77.
Naish, D. 2012. Why the world has to ignore ReptileEvolution.com. Tetrapod Zoology (direct link: http://blogs.scientificamerican.com/tetrapod-zoology/2012/07/03/world-must-ignore-reptileevolution-com/)
Unwin, D.M. and Bakhurina, N.N. 1995. Wing shape in pterosaurs. Nature 374, 316.

My response:
It is odd and unprofessional to attack the writer of a helpful comment (and his methods) while continuing to ignore the specimens of pes only tracks in the literature (see below).

With regard to Witton’s references, Bennett 2005 (writing in a fanzine) was correct in his assessment of earlier mistakes by Peters (also writing in a fanzine). None of this is in the academic literature.

On the same note, but elevated to the academic literature, Bennett (2007) made numerous observational errors (mistaking a maxilla for a sclerotic ring and ignoring the actual sclerotic rings, to name but a few). So mistakes happen. Corrections are made. This is the process of Science.

Evidently Witton does not forgive fanzine notions, but instead ascribes all future output as tainted. If so, then all of his example authors are likewise tainted:

Elgin, Hone and Frey (2011) made several mistakes in observations using crude cartoonish drawings to poorly trace subtle wing membranes, missing many details.

Hone, Sullivan and Bennett (2009) intended to disprove the universal hypothesis of parallel interphalangeal hinge lines, but avoided using all of the best examples (tetrapods with four and five digits). Even so they several times admitted to recovering hinge lines, even on three-toed taxa in which the digits were fully flexed and therefore not in their ‘useful’ positions.

In a blogpost Naish (2012) used artwork from paleoartists other than Peters to demean discarded hypotheses and observations, again (as above), not originating in the academic literature.

Unwin and Bakhurina (1995) failed to show the displacement of the left radius and ulna of their holotype Sordes specimen, which displaced the associated wing membrane and has since been misinterpreted as a leg-spanning uropatagium. No other pterosaur has documented a similar morphology. That is because this hypothesis is based on a misinterpretation/illusion.

Witton himself has employed imagination in his reproductions of an embryo pterosaur (Pterodaustro) with a large orbit and small rostrum when the data shows that all pterosaur embryos, juveniles and subadults had adult proportions, and in this regard are different than many other tetrapods. I could list many other observational errors.

It is important to show mistakes without rancor. It is also important not to dismiss all future output of a worker based on a few misinterpretations early in a career published in a fanzine. I certainly do not intend to brand any of the above workers the way Witton has branded Peters, but reserve the right to be critical, only if necessary, of any future output.

Bottom line, because there are several examples of bipedal pterosaur ichnites in the academic literature it is incumbent upon the author to address these examples and not ignore them. This is the academic forum for Witton to address his issues with all bipedal pterosaur tracks in the literature. It is also incumbent upon the author to treat peer-reviewed literature with more attention than he treats fanzines or blogposts that were not peer-reviewed.

References
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Conrad K, Lockley MG and Prince NK 1987. Triassic and Jurassic vertebrate-dominated trace fossil assemblages of the Cimarron Valley Region: Implications for paleoecology and biostratigraphy. New Mexico Geological Society Guidebook. 38th Field Conference, Northeastern New Mexico 1987. 127-138.
Lee YN, Azuma Y, Lee H-J, Shibata M, Lu J 2009. The first pterosaur trackways from Japan. Cretaceous Research 31, 263–267.
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

I’ll add here in conclusion
the current crop of pterosaur workers continues to wonder where pterosaurs originated, even though that was established 15 years ago. They continue to hold the purported uropatagium of Sordes as their paradigm, rather than recognize it for what it is, a taphonomic shift of wing elements. They do not recognize the digitigrade nature of basal pterosaur pedes despite the great match they make with Rotodactylus tracks, the only ichnites with digit 5 impressing far behind the other digits. And the list goes on. As Witton notes above, many current pterosaur workers consider my list of peer-reviewed academic literature unworthy of even considering. If it’s so wrong, it should be easy to dismantle. But to ignore this literature is to keep the blinders on.

And that’s why this blogpost continues…

And Mark Witton, if you’re reading this:
don’t believe anything I write, but please do check out for yourself the Triassic and Jurassic pterosaur specimens and gauge them against the tracks I suggest were made by them.

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