SVP abstracts 9: Pushing a tiny wading pterosaur into the deep end

Habib, Pittman and Kaye 2020
add laser fluorescence to a tiny pterosaur, the still unnamed Berlin specimen, MB.R.3531 (Figs. 1a, b) we first looked at following Flugsaurier 2018.

From the Habib et al. abstract:
“Water launch capacity has been previously suggested for some marine pterosaurs based on osteological grounds, but robust estimates of specimen-specific performance are difficult without robust estimates of wing area and potential hindfoot webbing. Here, we provide the first estimates of pterosaur water launch performance that take into account preserved soft tissue anatomy.”

FIgure 1. Reconstruction of MB.R.3531, nesting with Eoazhdarcho, Eopteranodon and Aurorazhdarcho.

FIgure 1a. Reconstruction of MB.R.3531, nesting with Eoazhdarcho, Eopteranodon and Aurorazhdarcho. Shown about actual size, so this pterosaur could have stood upright like this in a 10cm per side box. See figure 1b.

Figure 1. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx to scale.

Figure 1b. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx (not a juvenile) to scale. The smaller one had better stay out of deeper waters.

Continuing from the Habib et al. abstract:
“The aurorazhdarchid pterosaur specimen MB.R.3531 from the Upper Jurassic Solnhofen Limestone was imaged using Laser-Stimulated Fluorescence, revealing significant soft tissue preservation. These soft tissues are among the best-preserved of any known Jurassic pterosaur, including for the first time, a complete actinofibrillar complex, an undistorted actinopatagium with the retrophalangeal connective tissue wedge and entire trailing edge, and webbed feet.”

Why the showmanship (= hyperbole, = falsehood)? Most of these traits have been known for several pterosaurs and from less jumbled specimens, including the  Zittel wing specimen of Rhamphorhynchus (Fig. 2), the dark-wing specimen of Rhamphorhynchus and the Vienna specimen of Pterodactylus (Fig. 3).

The Zittel wing

Figure 2. The Zittel wing from a species of Rhamphorhynchus. This is real. There is no way this wing membrane is going to stretch to the ankles. See figure 3 for comparison and phylogenetic bracketing. This is how pterosaur wings were able to be folded away when not in use. 

Figure 2. Here is the Vienna specimen of Pterodactylus in situ and with matrix removed. Now compare this figure with figure 3, which shows the wings and uropatagia unfolding. There is no way to turn this into a deep chord wing membrane. And it decouples the forelimbs from the hind limbs.

Figure 3. Here is the Vienna specimen of Pterodactylus in situ and with matrix removed. Now compare this figure with figure 3, which shows the wings and uropatagia unfolding. There is no way to turn this into a deep chord wing membrane. And it decouples the forelimbs from the hind limbs. This is how pterosaur wings were able to be folded away when not in use. 

Continuing from the Habib et al. abstract:
“These physically validated soft tissues formed the basis for analyzing water launch capability in MB.R.3531. We modeled the water launch as quadrupedal and broadly similar to modern “puddle jumping” anseriform birds that use a combination of their webbed feet and partially folded wings to push against the water surface during takeoff.”

More myth-making. Like the morphologically similar by convergence, Pterodactylus (based on the Vienna specimen; Figs. 3, 4), MB.R.3531 was a quadrupedal wader (note the tiny fore claws), but able to stand bipedally prior to take-off. Waders don’t get themselves into water too deep to touch the substrate. Ask any sandpiper, plover or stilt.

So this is much ado about nothing, based on putting the discredited Habib method of pushup take-off back on the table.

FIgure 6. Pterodactylus scolopaciceps (n21) model. Full scale.

Figure 4. Pterodactylus scolopaciceps (n21) model. Full scale. This is how pterosaur wings were able to be folded away when not in use. 

More from the Habib et al. abstract:
“Under this model, both hind limb and forelimb contact areas are critical. Under conservative assumptions regarding power and range of motion, we predict that MB.R.3531 was capable of rapid takeoff from the water surface.

Yes, of course, but from a bipedal start (Fig. 5). And from shallow ponds, no deeper than knee deep.

FIgure 8. Dimorphodon take off (with the new small tail).

FIgure 5. Dimorphodon take off (with the new small tail).

From the Habib et al. abstract:
“Our model predicts that water launch performance in pterosaurs was particularly sensitive to three factors: available propulsive contact area, forelimb extension range, and extension power about the shoulder. MB.R.3531 possessed both osteological and soft tissue features that significantly enhanced these performance characteristics (including, but not limited to, expanded internal rotator/extensor attachments on the proximal humerus, extended humeral length, chordwise distal actinofibril orientation, and webbed pes).”

If you’ll compare one with another, MB.R.3531 (Fig. 1) is convergent in most respects to a typical Solnhofen Pterodactylus (Fig. 4), down to the webbed feet. There was nothing out of the ordinary about MB.R.3531.

“These features would have limited impact on flight performance. We therefore interpret them as likely water takeoff specializations.

Whoa, partner! These traits are typical of most beach combing pterosaurs, so far as they can be determined in fossils and phylogenetic bracketing, even with unrelated clade convergence.

“The osteological specializations in MB.R.3531 are subtle, which may be related to its small size.”

I would agree that the osteological specializations are so subtle they do not exist.

“Larger marine pterosaurs appear to exaggerate these characteristics, which matches expectations from scaling.

This is false. Ornithocheirids have notoriously tiny feet, unsuitable for anything more than standing still and walking slowly. More to come.

“We show that soft tissue data can be used to help validate the dynamic feasibility of water launch in pterosaurs, suggesting it was a regular part of foraging behavior in some taxa.”

This is false. Dr. Habib, just let the pterosaur stand upright, as its ancestors did and as it was designed to do (fused sacrals and fused dorsal vertebrae dorsally, sternum + gastralia + prepubes support ventrally). Quadrupedal pterosaur tracks are more prevalent because they were made by a few clades of small-fingered beach combing pterosaurs, principally pterodactylids, ctenochasmatids and azhdarchids (Peters 2011).

Pelican take-off sequence from water.

Figure 6. Pelican take-off sequence from water using kicking webbed feet and elevated, then flapping wings simultaneously. Click to enlarge.

From an earlier 2018 assessment of MB.R.3531:
Habib and Pittman 2018 bring us a rarely studied Berlin pterosaur, MB.R.3531 (Fig. 1) originally named Pterodactylus micronyx, then Aurorazhdarcho micronyx. This specimen nests with other wading pterosaurs, AurorazhdarchoEopteranodon and Eoazhdarcho forming  a clade overlooked by other workers, at the transition between germanodactylids and pteranodontids, not related to azhdarchids (Peters 2007).

For those wondering why I don’t publish more.
Why put in the effort if competing studies are ignored? The online way is faster, briefer and can be animated with no color charges. Furthermore, the vetting process prior to publication of hypotheses like the dangerous pushup launch and the bat-wing pterosaur membrane myth, is failing time and again. Editors, professors and researchers who should be earning their paycheck from rigorously testing new hypotheses are instead granting their friends free passes in an effort to keep the status quo in lectures and textbooks.


References
Habib M and Pittman M 2018. An “old” specimen of Aurorazhdarcho micronyx with exceptional preservation and implications for the mechanical function of webbed
feet in pterosaurs. Flugsaurier 2018: The 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts: 41–43.
Habib MB, Pittman M and Kaye T 2020. Pterosaur soft tissues revealed by laser-stimulated fluorescence enable in-depth analysis of water launch performance. SVP abstracts 2020.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2010. In defence of parallel interphalangeal lines.
Historical Biology 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. http://dx.doi.org/10.1080/10420940.2011.573605

https://pterosaurheresies.wordpress.com/2018/03/23/pteranodon-quad-hopping-water-takeoff-according-to-the-amnh/

https://pterosaurheresies.wordpress.com/2018/08/12/flugsaurier-2018-web-footed-little-pterosaur-mb-r-3531/

https://pterosaurheresies.wordpress.com/2012/12/16/water-takeoff-in-a-pelican-part-2-with-reference-to-pterosaur-water-takeoffs/

https://pterosaurheresies.wordpress.com/2015/03/23/amnh-animated-pterosaur-takeoffs/

https://pterosaurheresies.wordpress.com/2012/04/07/pterosaur-take-off-from-water/

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

https://pterosaurheresies.wordpress.com/2015/05/23/pterosaur-launch-talk-from-2012-on-youtube/

Upper Jurassic tidal flat pterosaur tracks from Poland

Note:
The following is from an unedited manuscript accepted for publication and pre-published online. The editors note: copyediting may change the contents by the time this is officially published. Not sure why the editors are going this route, except for comment and validation. Hope this gets back to them for the help it offers.

Elgh et al. 2019 report,
“In this paper, we report newly discovered, well-preserved pterosaur track material.”

The authors mistakenly report, 
“Intermediates between most of these states can be seen in the non-pterodactyloid
groups most closely related to the pterodactyloids, e.g. the rhamphorhynchids and wukongopterids” 

No, tiny dorygnathids and scaphognathids are transitional taxa when more taxa are added in the large pterosaur tree (LPT, 238 taxa). Wukongopterids are a sterile lineage, otherwise known as a dead end. There are 4 convergent pterodactyloid-grade clades. All these are recovered by adding taxa without bias.

The authors mistakenly report,
“As noted previously, digit V differs greatly between non-pterodactyloids and pterodactyloids. In non-pterodactyloids this digit is long and supported the uropatagium.”

No, the long and unique fifth digit is found in tanystropheids, langobardisaurids and fenestrasaurs like Cosesaurus and Sharovipteryx. No pterosaur fossil shows uropatagial support. This is a myth. Exceptionally, and for hind wing gliding, each uropatagium extends nearly to the tip of digit 5 in Sharovipteryx.

The authors mistakenly report, 
“Furthermore, pterodactyloids lost their teeth in several lineages, something not seen among nonpterodactyloids.” 

Adding taxa recovers four pterodactyloid-grade clades, as shown by LPT. Two arise from distinct lineages within Dorygnathus. Two others arise from tiny descendants of Scaphognathus. One clade from each lineage produces toothless taxa.

The authors mistakenly report,
“The non-wing bearing digits are much shorter and increase in length from IIII.” 

Typically, yes, but not always. Sometimes all three small phalanges are sub-equal in length.

The authors mistakenly report, 
“Their phalangeal formula is 2-3-4-4, since the wing finger ungual is lost.”

Not true. I have shown many examples of a wing ungual.

The authors mistakenly report, 
“The pes has five digits with a phalangeal formula of 2-3-4-5-2. The penultimate phalanx is elongated in digits I-IV.”

Not true. Pterodaustro (Fig. 1) and several other beach coming pterosaurs do not have elongate penultimate pedal phalanges. The authors cite the invalidated paper by Unwin 1996, rather than Peters 2011, which compared and showed many examples of pterosaur feet and tracks.

Figure 1. A selection of ctenochasmatid feet. Note the short penultimate phalanges (green).

Figure 1. A selection of ctenochasmatid feet from Peters 2011. Note the short penultimate phalanges (green) are not longer than the longest phalanx in series.

The authors mistakenly report,
“The wukongopterids, being the non-pterodactyloid group(s) most closely related to the pterodactyloids have, as with many characters, an intermediate state with a fifth digit that is shorter than in other non-pterodactyloids but longer than in pterodactyloids.”

Not true. Wukongopterids generally have a larger pedal digit 5 than in many other basal pterosaurs and are not related to derived pterosaurs despite several traits that converge. As mentioned above, phylogenetic miniaturization occurred 4 times in the ancestry of the 4 pterodactyloid-grade pterosaurs.

The authors mistakenly report, 
“It is unclear how the fifth digit functioned in terrestrial locomotion in all groups of pterosaurs.” 

Not true. Peters 2000 and 2011 showed exactly how pedal digit 5 was used with comparable tracks and hypothetical perching situations.

To eliminate considering the above issues, the authors report,
“no exhaustive morphometrical methods compare pes and manus impressions with anatomical details to pes and manus body fossils have been made. The most creative attempt to match pes anatomy to tracks by Peters (2011) regrettably introduces too many speculations to be of use in this study.”

That’s how it works, folks. Like Hone and Benton, 2007 and 2009, many pterosaur workers prefer to toss out data that challenges traditions. On the plus side: doing so ensures publication in the present academic climate.

No longer requiring personal examination
of fossils, the authors report, “The Anurognathus ammoni described by Döderlein (1923) was measured using an image of the specimen published by David Hone online (here). The A. ammoni described by Bennett (2007b) was measured using an image published on the pterosaur.net website (here).”

Elgh et al. present several images of
pedal impressions, but they are isolated, so there is no confirmation of left or right identity. This is critical as some pterosaurs have a longest pedal digit 2, while others have a longest pedal digit 3. Others are sub equal. When three ungual bases are collinear most of the time those are digits 2–4, but not always. One Rhamphorhynchus specimen and Nemicolopterus goes the other way.

That statistic has implications for Elgh et al.
who identify four traced fossils with unguals aligned with digit 3 often the longest.

Below
I employ the first photo and first drawing by Elgin et al. (Fig. 2) and find an overlooked pedal morphology (in color overlay) and a strong similarity to an Early Cretaceous Beipiaopterus, a taxon not mentioned in the authors’ current text. Having a pedal digit 1 similar in length to the other three medial toes is very rare, so many other candidates are readily eliminated leaving this one and few to no others. Beipiaopterus nests in the LPT between a series of dorygnathids and a series of pre-azhdarchids, some of them from Solnhofen sediments.

Figure 1. Left and center images from Elgh et al. Colors and pes of Beipiaopterus added for comparison.

Figure 2. Left and center images from Elgh et al. Colors and pes of Beipiaopterus added for comparison.

Elgh et al. made no effort
at locating pedal pads or joints that correspond to pad/joint patterns in pterosaur pedes. By contrast, coloring the track reveals a typical pterosaur pes with a typical pad/joint pattern, but atypical phalanx lengths.

No pterosaur pedes in Peters 2011 are a perfect match,
but Early Cretaceous Beipaiopterus comes close.

Note that Elgh et al. ignored the curved impression
made by the elongate digit 5—because they were married to traditional paradigms, instead of going with the data as is.

I can only wish, at this point,
that future pterosaur workers add more precision to their studies and consider all possibilities… rejecting traditional hypotheses that cannot be validated, while embracing hypotheses that reflect reality.


References
unedited manuscript accepted for publication:
Elgh E, Pieńkowski G and Niedźwiedzki G 2019. Pterosaur track assemblages from the Upper Jurassic (lower Kimmeridgian) intertidal deposits of Poland: Linking ichnites to potential trackmakers, Palaeogeography, Palaeoclimatology, Palaeoecology, https://doi.org/10.1016/j.palaeo.2019.05.016
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18, 114-141.
Unwin DM 1996. Pterosaur tracks and the terrestrial ability of pterosaurs. Lethaia 29, 373-386.

Giant Alaska pterosaur tracks indicate floating pterosaurs

Figure 1. Pterosaur tracks from Alaska. Note the lack of pedal tracks and the large size of the manus tracks.

Figure 1. Pterosaur tracks from Alaska. Note the lack of pedal tracks and the large size of the manus tracks.

Figure 2. Closeup of a giant pterosaur manus track. Digits identified.

Figure 2. Closeup of a giant pterosaur manus track. Digits identified.

A recent paper ( ) described giant Late Cretaceous pterosaur tracks from the far north in Alaska. These are likely made by large azhdarchids, like Quetzalcoatlus.

At 18 centimeters long by 6 centimeters wide, the bigger pterosaur tracks are “very large” compared to others that have been reported, Fiorillo’s team says.

The more diminutive set of prints, meanwhile, was only about one-fourth as large — about 6 centimeters by 4 centimeters.

Manus only tracks were likely produced by floating and poling pterosaurs as we talked about earlier with Tapejara. Here the size and proportions of the manus tracks, along with the location and time period all point toward giant azhdarchids.

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.

It is important to appreciate the great size of the pterosaurs that made such large manus tracks, especially so since the fingers that made the impressions are among the smallest parts on the pterosaur itself.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 4. Quetzalcoatlus specimens to scale. Here digit 3 is approximately 18 cm long, matching the size of the track. The manus of Quetzalcoatlus is poorly known. These are based on Zhejiangopterus and Azhdarcho. The second finger could have been shorter to match the tracks. The ability of digit 3 to rotate posteriorly harkens back to the lepidosaur ancestry of pterosaurs.

Manual 3.1 of Azhdarcho (Fig. 4) shows how that digit was able to bend posteriorly. Like most lizards, the fingers were rather free to rotate on bulbous articular surfaces.

Figure 2. Manual 3.1 for Azhdarcho. Note the bulbous proximal portion.

Figure 5. Manual 3.1 for Azhdarcho. Note the bulbous proximal portion enabling posterior bending.

 

References
Fiorillo AR et al. 2009. A pterosaur manus track from Denali National Park, Alasak range, Alaska, United States. Palaios 24: 466-472.

Fiorillo AR et al. 2014. Pterosaur tracks from the Lower Cantwell Formation (Campanian–Maastrichtian) of Denali National Park, Alaska, USA, with comments about landscape heterogeneity and habit preference. Historical Biology DOI:10.1080/08912963.2014.933213

Online report.

 

New dsungaripterid (?) walking track

A new large pterosaur track
attributed to a dsungaripterid has been published (He et al. 2013, Fig. 1).

Unfortunately,
I know of only one dsungaripterid pes, that of Noripterus

Fortunately,
it’s a pretty good match. I suspect that much more is known of another dsungaripterid, Dsungaripterus, but the pes and manus have not been published yet. Send that data if you have it.

Other related taxa
from the Tapejaridae, like Huaxiapeterus and Tapejara, have very similar pedal proportions, but a longer manual digit 1. They are still possible candidates.

 

Figure 1. New possible dsungaripterid track *He et al. 2013) compares favorably to Noripterus, a dsungaripterid pterosaur. Note the metatarsal spread and likely finger 3 drag mark. The metatarsophalangeal joints must have been very loose to enable the wide splay seen in the track. Also note the precision of the pes versus the expansion of the manus track.

Figure 1. Click to enlarge. New possible dsungaripterid track (He et al. 2013) compares favorably to Noripterus, a dsungaripterid pterosaur. Note the metatarsal spread and likely finger 3 drag mark. The metatarsophalangeal joints must have been very loose to enable the wide splay seen in the track. Also note the precision of the pes versus the expansion of the manus track.

Since footprints are so plastic during their creation,
some are very difficult to identify. Nevertheless, these impressions are impressive! He et al (2013) did not illustrate the ungual of digit 4, so if there was no ungual, or if the ungual extended only as far as the impression indicates (Fig. 1), then different taxa become candidates (those with a short digit 4), not dsungaripterids or tapejarids.

The manus
of Noripterus essentially matches the printmaker in having a very short, slender  digit 1 and a large robust digit 3 with p3.2+p3.2 shorter in sum than p3.1. Again, I have no manus data for Dsungaripterus. Send it if you do.

Manus vs pes impression
Here the pes impression shows more detail than the manus. Moreover, the manus impression is quite fat compared to the slender finger bones. Why is this so? If you just look at the skeleton it appears that there is no room for that much flesh around digit 3. But data is data. Could the method of implantation of the manus, with a little more speed perhaps, create a little  crater around it? Or did the manus shift laterally during the step cycle contact? Whatever the answer, such impressions are common to a wide range of quadrupedal pterosaur trackmakers.

References
He Q, Xing L, Zhang J, Lockley MG, Klein H, Persons S4, Qi L and Kia C 2013. New Early Cretaceous Pterosaur-Bird Track Assemblage from Xinjiang, China: Palaeotheolgy and Palaeoenvironment. Acta Geologica Sinica (English Ed.) 87(6):1477-1485. pdf

Pterosaurs were likely floaters: evidence from manus only tracks

Yesterday we reviewed Hone and Henderson (2013) who conducted computational experiments with four misbegotten digital pterosaur models and reported that pterosaurs were unlikely floaters that would have struggled to keep their noses above the surface and so risked drowning, despite their air-filled skeletons.

Unfortunately
the Hone and Henderson results don’t agree with the facts as told by manus-only tracks, that can only be made by floating pterosaurs. As Hone has done in previous papers, these are all conveniently omitted. Case in point: the Summerville tracks (Lockley et al. 1996, Fig. 1).

Summerville tracks matched to potential trackmaker, Jidapterus, a basal azhdarchid.

Figure 1. Summerville tracks matched to potential trackmaker, Jidapterus, a basal azhdarchid pterosaur using a poling technique to produce manus-only tracks while floating.

Summerville (Late Jurassic) manus only tracks (Fig 1), likely made by a sister to Jidapterus, a protoazhdarchid with rather big fingers.

Is this the only explanation?
Oh, sure some have said that pterosaurs pressed their hands more deeply into the matrix and footprints were thereafter erased by geological processes. But doesn’t this strike you as trying to make excuses, on the order of Elgin, Hone and Frey’s infamous “membrane shrinkage“?

Figure 2. Manus only tracks of pterosaurs, Late Jurassic to Late Cretaceous.

Figure 2. A catalog of manus only tracks of pterosaurs, Late Jurassic to Late Cretaceous. Note the odd and large Las Hoyas track is now considered to be made by a theropod, which makes perfect sense.

The large Las Hoyas track
is impossible to fit to a pterosaur manus. No pterosaur has a longer and more robust manual digit 2 than 3. Some have these two digits subequal in length, but to scale these up to the track size creates a truly gigantic pterosaur. Vullo et al. 2009 got it right when they decided it belonged to a theropod dinosaur foot.

Figure 4. Tapejara compared to Albian tracks from South America. They are a close match in size and shape.

Figure 4. Tapejara compared to Albian tracks from  west-central Argentina (Calvo and Lockley 2001). They are a close match in size and shape. Pedal digits 2-4 are subequal and digit 1 is slightly shorter. Scale bars for tracks and pterosaur match. Footprints indicate no splay in the digits. Note the comparative sizes of the manus and pes.

The “first Gondwana pterosaur tracks” (Calvo and Lockley 2001) can all be matched to Tapejara-like (Fig. 4, 5) trackmakers. The Candeleros Member of the Rio Limay Formation (Albian–Cenomanian) at Lake Ezequiel Ramos Mexía, Neuquén Province, Argentina is contemporary with Tapejara bones on the east coast of Brazil. The palaeoenvironmental setting of the track beds was a lake shoreline, where dinosaur tracks also occur.

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

Figure 5. Tapejara poling while floating, producing manus-only Albian tracks from west-central Argentina, all to scale .

Above, manus only tracks (Calvo and Lockley 2001) matched to Tapejara.

Figure 5. Price (Utah, Maastrichtian) tracks. These match up pretty well to Cycnorhamphus, except for size. Luckily we know of giant cycnorhamphids like Moganopterus, shown as a skull here to scale.

Figure 5. Price (Utah, Maastrichtian) tracks. These match up pretty well to Cycnorhamphus, except for size. Luckily we know of giant cycnorhamphids like Moganopterus, shown as a skull here to scale. Unfortunately, Moganopterus is from the Early Cretaceous of China.

Moganopterus, a cycnorhamphid, is a good model for the trackmaker of the Maastrichtian Price (Utah) racks, merely with a shorter digit 2 than Cycnorhamphus (Fig. 5). Unfortunately Moganopterus is from the Early Cretaceous of China.

If you’re interested
in finding a better match for any of these tracks, you are welcome to try. I had a catalog of pterosaur manus and pedes at reptileevolution.com and a matrix of pterosaur traits that made my search go rather quickly.

References
Calvo JO and Lockley MG 2001. The first pterosaur tracks from Gondwana. Cretaceous Research 22:585-590.
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Hone DWE, Henderson DM 2013. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats, Palaeogeography, Palaeoclimatology, Palaeoecology (2013 accepted manuscript), doi: 10.1016/j.palaeo.2013.11.022
Lockley MG, Logue TJ, Moratalla JJ, Hunt AP, Schultz RJ and Robinson JW 1995.  The fossil trackway Pteraichnus is pterosaurian, not crocodilian: implications for the global distribution of pterosaur tracks. Ichnos, 4: 7–20.
Lockley MG, Hunt AP and Lucas SG 1996. Vertebrate track assemblages from the Jurassic Summerville Formation and correlative deposits. – In: Morales M. (Ed.), The Continental Jurassic. Museum of Northern Arizona Bulletin, 60: 249–254.
Lockley MG and Wright JL 2003. Pterosaur swim tracks and other ichnological evidence of behavior and ecology. – In: Buffetaut E and Mazin JM (Eds), Evolution and Paleobiology of Pterosaurs; Geological Society, London, Special Publications 217:297-313.
Lockley M, Harris JD and Mitchell L 2008. A global overview of pterosaur ichnology: tracksite distribution in space and time. Zitteliana B28: 185-198.pdf
Mickelson DL, Lockley MG, Bishop J, Kirkland J 2004. A New Pterosaur Tracksite from the Jurassic Summerville Formation, Near Ferron, Utah. Ichnos, 11:125–142, 2004
Parker L and Balsley J 1989. Coal mines as localities for studying trace fossils. In: Gillette DD and Lockley MG (Eds), Dinosaur Tracks and Traces; Cambridge (Cambridge University Press), 353–359.
Pascual Arribas C and Sanz Perez E 2000. Huellas de pterosaurios en el groupo Oncala (Soria España). Pteraichnus palaciei-saenzi, nov. ichnosp.  Estudios Geologicos, 56: 73–100.
Vullo R, Buscalioni A D, Marugán-Lobón J and Moratalla JJ 2009. First pterosaur remains from the Early Cretaceous Lagerstätte of Las Hoyas, Spain: palaeoecological significance. Geological Magazine, 146: 931-936.