A new look at Jidapterus (basal azhdarchid pterosaur)

Wu, Zhou and Andres 2017
bring us long anticipated details on Jidapterus (Early Cretaceous, Dong, Sun and Wu 2003) which was previously presented as a small in situ photograph lacking details. Even so a reconstruction could be made (Fig. 1). Coeval larger tracks (Elgin and Frey 2011) have been matched to that reconstruction.

Figure 2. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton.

Figure 1. Jidapterus matched to the Gansu, Early Cretaceous pterosaur tracks. The trackmaker was one-third larger than the Jidapterus skeleton.

Of interest today
is the fact that Jidapterus was originally and, so far, universally considered toothless. Its specific name, J. edentatus, refers to that condition. Wu, Zhou and Andres 2017 produced tracings (Figs. 2, 3) of the rostrum that are also toothless. However, they are crude and appear to miss the premaxilla and maxilla sutures, the palatal elements… and maybe some teeth. Those jaw rims are not slippery smooth like those of Pteranodon. Outgroups in the large pterosaur tree (LPT), all have tiny teeth.

Figure 2. Rostrum of Jidapterus (RCPS-030366CY) and traced according to Wu et al. and colorized using DGS to reveal skull sutures and possible teeth.

Figure 2. Rostrum of Jidapterus (RCPS-030366CY) and traced according to Wu et al. and colorized using DGS to reveal skull sutures and possible teeth. See figure 3 for details. What Wu, Zhou and Andres label the  “low ridge of rostrum” is here identified as the rostral margin above the palatal portion. 

The cladogram of Wu, Zhou and Andres
lacks dozens of key taxa found in the LPT that separate azhdarchids from convergent tapejarids and shenzhoupterids. In the LPT giant azhdarchids arise from tiny toothy azhdarchids once considered Pterodactylus specimens… and these, in turn are derived from tiny and mid-sized dorygnathids in the Middle Jurassic.

What Wu, Zhou and Andres label the  “low ridge of rostrum”
is here identified as the rostral margin rim at the edge of the palate.

Figure 3. Focus on the rostral tip of Jidapterus shown in figure 2. Are these teeth?

Figure 3. Focus on the rostral tip of Jidapterus shown in figure 2. Are these teeth? You decide. I present the data. 

As in all pterosaurs
each premaxilla of Jidapterus has four teeth according to this data.

Are these tiny teeth?
Or are they tiny occlusions and/or chisel marks. Let’s get even better closeups to figure this out. Phylogenetic bracketing indicates either tiny teeth or edentulous jaws could be present here.

References
Dong Z, Sun Y and Wu S 2003. On a new pterosaur from the Lower Cretaceous of Chaoyang Basin, Western Liaoning, China. Global Geology 22(1): 1-7.
Elgin and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1
Wu W-H, Zhou C-F and Andres B 2017. The toothless pterosaur Jidapterus edentus (Pterodactyloidea: Azhdarchoidea) from the Early Cretaceous Jehol Biota and its paleoecological implications. PLoS ONE 12(9): e0185486.

wiki/Jidapterus

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Versperopterylus (Lü et al. 2017) did not have a reversed first toe

And this specimen PROVES again
that anurognathids DID NOT have giant eyeballs in the anterior skull.

Figure 1. Vesperopterylus in situ. There is nothing distinct about pedal digit 1.

Figure 1. Versperopterylus in situ. There is nothing distinct about pedal digit 1.

Lü et al. 2017 bring us a new little wide-skull anurognathid
Versperopterylus lamadongensis (Lü et al. 2017) is a complete skeleton of a wide-skull anurognathid. It was considered the first pterosaur with a reversed first toe based on the fact that in digit 1 the palmar surface of the ungual is oriented lateral while digis 2–4 the palmar surfaces of the unguals are medial. That is based on the slight transverse curve of the metatarsus (Peters 2000) and the crushing which always lays unguals on their side. In life the palmar surfaces were all ventral and digit 1 radiated anteriorly along with the others.

Figure 2. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it. 

Figure 2. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it.

Lü et al were unable to segregate the skull bones.
Those are segregated by color here using DGS (Digital Graphic Segregation). See below. Some soft tissue is preserved on the wing. Note: I did not see the fossil first hand, yet I was able to discern the skull bones that evidently baffled those who had this specimen under a binocular microscope. Perhaps they were looking for the giant sclerotic rings in the anterior skull that are not present. Little ones, yes. Big ones, no.

Figure 1. Vesperopterylus skull with bones identified by DGS (digital graphic segregation). Lü et al. were not able to discern these bones and so left the area blank in their tracing. Note the complete lack of a giant eyeball in the front of the skull. Radius and ulna were removed for clarity and to show a complete lack of giant eyeballs (sclerotic rings) in the anterior skull. 

Figure 1. Versperopterylus skull with bones identified by DGS (digital graphic segregation). Lü et al. were not able to discern these bones and so left the area blank in their tracing. Note the complete lack of a giant eyeball in the front of the skull. Radius and ulna were removed for clarity and to show a complete lack of giant eyeballs (sclerotic rings) in the anterior skull.

This skull reconstruction
(Fig. 4) is typical of every other anurognathid, because guesswork has been minimized here. After doing this several times with other anurognathids, I knew what to look for and found it. No giant sclerotic rings were seen in this specimen.

Figure 4. Vesperopterylus skull reconstructed from color data traced in figure 3.

Figure 4. Versperopterylus skull reconstructed from color data traced in figure 3. Due to the angled sides of the skull some foreshortening was employed  to match those angles. Original sizes are also shown.

With regard to perching
all basal pterosaurs could perch on branches of a wide variety of diameters by flexing digit 1–4 while extending digit 5, acting like a universal wrench (Peters 2000, FIg. 5). This ability has been overlooked by other workers for the last two decades,

Figure 1. The pterosaur Dorygnathus perching on a branch. Above the pes of Dorygnathus demonstrating the use of pedal digit 5 as a universal wrench (left), extending while the other four toes flexed around a branch of any diameter and (right) flexing with the other four toes. As in birds, perching requires bipedal balancing because the medially directed fingers have nothing to grasp.

Figure 1. The pterosaur Dorygnathus perching on a branch. Above the pes of Dorygnathus demonstrating the use of pedal digit 5 as a universal wrench (left), extending while the other four toes flexed around a branch of any diameter and (right) flexing with the other four toes. As in birds, perching requires bipedal balancing because the medially directed fingers have nothing to grasp.

I have not yet added Versperopterylus
to the large pterosaur tree.

References
Lü J-C et al. 2017. Short note on a new anurognathid pterosaur with evidence of perching behaviour from Jianchang of Liaoning Province, China. From: Hone, D. W. E., Witton MP and Martill DM(eds) New Perspectives on Pterosaur Palaeobiology.
Geological Society, London, Special Publications, 455, https://doi.org/10.1144/SP455.16
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. 
Ichnos, 7: 11-41

 

New online course on birds and pteros from Dr. Phil Currie

This is part of a new video series on theropods and birds
Click to view. YouTube video on birds and pterosaurs from Dr. Phil Currie

Click to view. YouTube video on birds and pterosaurs from Dr. Phil Currie

YouTube caption:
Week 4, Lecture 3 for the online course “Paleontology: Theropod Dinosaurs and the Origin of Birds”, taught by Philip John Currie, Ph.D. All rights belong to Coursera and University of Alberta. For educational purposes only. Happy learning!
The new video
features all your favorites: Microraptor, Archaeopteryx, Deinonychus and some old John Ostrom hypotheses.
I added this comment:
The use of cartoons without skeletons undermines the scientific value of this project.
Microraptor does not nest with dromaeosaurids in the large reptile tree, but with Ornitholestes and tyrannosaurs.
That cladogram does not document a secondary flightless condition in dromaeosaurids.
Pterosaurs are not related to dinosaurs, but are tritosaur lepidosaurs derived from taxa like Huehuecuetzpalli, Macrocnemus and Cosesaurus.
Pterosaur flight membrane does not attach to the lower leg. See

New Como Bluff (Latest Jurassic) pterosaurs

Bits and pieces
of new Latest Jurassic pterosaurs are coming out of aquatic deposits in western North America according to McLain and Bakker 2017. The material is 3D and not very mineralized, so it is extremely fragile.

Specimen(s) #1 – HMNS/BB 5027, 5028 and 5029
“One proximal and two distal femora match a complete femur (BYU 17214) referred to Mesadactylus. Unexpectedly, both of the BBF distal femora possess a large intercondylar pneumatopore. BYU 17214 also possesses an intercondylar pneumatopore, but it is smaller than in the BBF femora. Distal femoral pnuematicity is previously recognized only in Cretaceous azhdarchoids and pteranodontids.”

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

Figure 1. The Mesadactylus holotype (Jensen and Padian 1989) nests with the North American anurognathids. Several referred specimens (Smith et al. 2004), when reconstructed nest at the base of the azhdarchidae, with Huanhepterus and the flightless pterosaur SOS 2428.  The new BYU 17214 femur is essentially identical to the femur shown here.

Earlier we looked at two specimens referred to Mesadactylus. One is an anurognathid (Fig. 1). The other is a basal azhadarchid close to Huanhepterus, not far removed from its Dorygnathus ancestors in the large pterosaur tree. Instead McLain and Bakker compare the femora with unrelated and Early Cretaceous Dsungaripterus, which convergently has a similar femur. The better match is to the basal azhdarchid, so distal femoral pneumaticity does not stray outside of this clade. By the way, it is possible that Mesadactylus was flightless.

Specimen(s) #2 – HMNS/BB 5032 (formerly JHU Paleon C Pt 5)
“A peculiar BBF jaw fragment shows strongly labiolingually compressed, incurved crowns with their upper half bent backwards; associated are anterior fangs. We suspect this specimen is a previously undiagnosed pterosaur.”

These toothy specimens were compared to two Early Cretaceous ornithocheirids, one Middle Jurassic dorygnathid, and one Latest Jurassic bird, Archaeopteryx. None are a good match. A better, but not perfect,match can be made to the Early Jurassic pre-ctenochasmatid, Angustinaripterus (Fig. 2) which has relatively larger posterior teeth than does any Dorygnathus specimen.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

The HMNS BB 5032 specimen(s) probably belong to a new species of Angustinaripterus or its kin based on the relatively large posterior teeth not seen among most Dorygnathus specimens.

As before,
we paleontologists don’t always have to go to our ‘go to’ taxon list of familiar fossils. Expand your horizons and take a fresh look at some of the less famous taxa to make your comparisons. You’ll find a good place to start at ReptileEvolution.com

References
McLain MA and RT Bakker 2017. Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff,
Wyoming, including a pterosaur with pneumatized femora.

Allkaruen koi was overlooked as a proto-Pterodaustro

A new pterosaur described by Codorniú et al. 2016
somehow escaped my notice until today. Allkaruen koi (Figs. 1,3,4) is the new genus. It was originally nested between basal (long-tailed) pterosaurs and the Darwinopterus clade + ‘Pterodactyloidea’ using an antiquated cladogram modified from Lü e al 2010, itself modified from Unwin 2003. We’re going to critically examine this paper, applying logic, creating reconstructions, calling on overlooked data and including more than a few previously excluded taxa.

Figure 1. Allkaruen elements as originally published.

Figure 1. Allkaruen elements as originally published. Some of the scale bars are different by 94% and 117%, resized to the same scale below in figure 3. Why couldn’t they all be drawn to the same scale, and in relation to one another? You’ll see how well that works in figure 3.

The holotype of Allkaruen koi includes:

  1. MPEF-PV 3613 (Museo Paleontológico Egidio Feruglio)  braincase,
  2. MPEF-PV 3609 mandible
  3. MPEF-PV 3615 cervical vertebrae (Fig. 1)

The stratigraphic horizon
in which Allkaruen was found was labeled by Codorniú et al.: “latest Early-early Middle Jurassic.” Let’s just call it “Middle Jurassic.”

From the Codorniú et al. abstract
“Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved, uncrushed braincase that sheds light on the origins of the highly derived neuroanatomy of pterodactyloids and their close relatives. A mCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids.”

The diagnosis:
“Small pterosaur diagnosed by the following unique combination of skull characters present in the holotype (autapomorphies marked with asterisk):

  1. frontal with large pneumatic foramen on the postorbital process
  2. dorsal occiput faces posterodorsally and occipital condyle faces posteroventrally
  3. long, rod-like basipterygoid processes diverging at approximately 20–25 degrees.

The referred mandibular and vertebral materials also show a unique combination of characters that include:

  1. a long lower jaw with a concave profile in lateral view
  2. four-five large, septated, and well-separated anterior alveoli followed by a posterior alveolar groove*;
  3. mid-cervical vertebrae elongate with low neural arch and blade-like neural spine; pneumatic foramina on lateral surface of the centrum and peduncle of the neural arch
  4. reduced diapophyseal process lacking articular surface
  5. absence of accessory zygapophyseal processes.”
Codornií cladoram nesting Allkaruen between basal pterosaurs and derived pterosaurs.

Figure 2. Codornií cladoram nesting Allkaruen between basal pterosaurs and derived pterosaurs. Note that a dinosaur is the outgroup here. There are 59 taxa above. Note the close relationship of Dorygnathus and Allkaruen and Pterodaustro in this cladogram. It gets even closer in figure 6.

The Codorniú et al. phylogenetic analysis
Codorniú et al. added Allkaruen to the cladogram of Lü et al 2003 (the Darwinopterus study) based on Unwin 2003. They recovered Allkaruen basal to their ‘Monofenestrata, which was basal to their ‘Pterodactyloidea’. Both clades were found to be invalid in the large pterosaur tree.

Figure 3. Reconstruction of Allkaruen atop a more complete Pterodaustro to the same scale demonstrating a close match-up of elements.

Figure 3. Reconstruction of Allkaruen atop a more complete Pterodaustro to the same scale demonstrating a close match-up of elements that was somehow overlooked by the original authors. The amount of material missing between the mandibles and the cranium is unknown. See figure 4 for a closer look at the cranium. Note the tooth grooves and anterior alveoli in the top view of the dentary.

A reconstruction
missing from the original paper, but provided here (Fig. 3) provides an overlooked answer to the affinities of Allkaruen. This Middle Jurassic taxon closely matches Albian (latest Early Cretaceous) Pterodaustro, the only other South American pterosaur with a dorsally concave dentary (#1), an alveolar groove (#2), similar mid-cervical vertebrae (#3) and maybe traits #4 and #5, (hard to tell from the available data). The dorsal appearance of the cranium of Allkaruen also closely matches that of another ctenochasmatid, Gnathosaurus. Most to all Pterodaustro specimens are preserved in lateral view, so the dorsal appearance must be gained from closely related taxa. like Gnathosaurus, by phylogenetic bracketing.

Figure 4. Closeup of the cranium and brain scan of Allkaruen atop a ghosted to scale image of Pterodaustro demonstrating a close affinity that was somehow overlooked originally.

Figure 4. Closeup of the cranium and brain scan of Allkaruen atop a ghosted to scale image of Pterodaustro to scale demonstrating a close affinity that was somehow overlooked originally with that short taxon list.

Pterodaustro is distinct from other ctenochasmatids
in that it has typical tetrapod vertically oriented mandibles, rather than flattened (wider than tall) mandibles typical of other ctenochasmatids (Fig. 7). In addition Pterodaustro has upwardly curved jaw tips, a trait documented in Allkaruen, in which we can see the transition from a toothy dentary to one with grooves to accommodate the hundreds of needle-like filter teeth found in Pterodaustro. Not sure why, but this similarity was overlooked by Codorniü et al. It’s doubly puzzling because Dr. Codorniú has published extensively on Pterodaustro. The only time Pterodaustro was mentioned by Codorniú et al. was when they wrote, “The cavities that invade the basicranium are also large, equivalent to those observed in pterodactyloids such as Pterodaustro.”

Figure 4. Chronological evolution of Pterodaustro via Allkaruen, Angustinaripterus (Early Jurassic) and Dorygnathus (late survivor in the Middle Jurassic).

Figure 5. Chronological evolution of Pterodaustro via Allkaruen, Angustinaripterus (Early Jurassic) and Dorygnathus (late survivor in the Middle Jurassic).

The pterosaur phylogeny presented
by the large pterosaur tree (LPT, subset Fig. 5) provides a fast track evolution from derived dorygnathids, already demonstrating a wide radiation in the Early Jurassic, to ctenochasmatids like Allkaruen (Middle Jurassic) and Ctenochasma (Late Jurassic) that does not include the Darwinopterus clade as transitional taxa. In the LPT four clades evolved a complete set of pterodactyloid-grade traits. Two other clades, Anurognathidae and Wukongipteridae, independently evolved an incomplete set of pterodactyloid-grade traits. These led to invalid claims by Andres, Clark and Xu 2014 that anurognathids were basal to pterodactyloids and Unwin 2003 + Lü et al. 2010 that wukongopterids were basal to pterodactyloids. These claims were made with short, incomplete taxon inclusion lists that were shown to be lacking in pertinent taxa by the LPT.

Fig. 5. Subset of the LPT focusing on Dorygnathus clades that evolved to become ctenochasmatids and azhdarchids. This is what you get when don't exclude taxa the way Codorniú did.

Fig. 6. Subset of the argePT focusing on Dorygnathus clades that evolved to become ctenochasmatids and azhdarchids. This is what you get when don’t exclude taxa the way Codorniú did.

It’s no surprise that Allkaruen has transitional traits.
In the LPT it represents a transitional stage in the evolution of Pterodaustro from Angustinaripterus ancestors. Allkaruen nests with Pterodaustro in the LPT, but due to the headless D2514 ‘not Eosipterus‘ specimen adding Allkaruen creates a polytomy (Fig. 6). As earlier, no claim of ‘mosaic evolution‘ can be made by Codorniú et al. ‘Mosaic evolution’ has not been shown to exist in large gamut cladograms. Such claims by Codorniú et al. and others are the result of small cladograms grossly lacking in pertinent taxa.

A selection of valid Ctenochasma skulls

Figure 7. A selection of valid Ctenochasma skulls together with the two interpretations of Sos 2179 (in gray below). Note the phylogenetic miniaturization following Angustinaripterus.

Professional bias among paleontologists
and a refusal to test competing hypotheses of relationships (Peters 2000, 2007) led to the phylogenetic disaster presented by Codorniú et al. 2016. No one will ever be convinced that pterosaurs arose from Euparkeria + HerrerasaurusWorkers who do so open themselves up to ridicule. We don’t want that. It makes us all look bad. Adding taxa should solve the phylogenetic problems found in Codorniú et al. The LRT and LPT offer suggestions, but workers must put forth the effort. In Peters 2000 Cosesaurus, Sharovipteryerx and Longisquama were documented to demonstrate closer relationships to pterosaurs than dinosaurs and archosaurs can offer.

Was Allkaruen transitional between basal pterosaurs and pterodactyloids?
No. There is no valid monophlietic clade of pterodactyloids. At present, the best we can say is: Middle Jurassic Allkaruen is (time wise) transitional between Early Jurassic Angustinaripterus and Early Cretaceous Pterodaustro (Fig. 5). Allkaruen is a ctenochasmatid, plain and simple. It points to an earlier radiation of ctenochasmatids than the Solnhofen Late Jurassic. The cranial elements of Allkaruen might someday be matched to post-cranial elements now represented by the lower Yixian D2514 specimen wrongly attributed (by Lü et al. 2006) to Eosipterus. Or not. A complete specimen (crania + post-crania) would settle this  issue.

I can’t be the first pterosaur worker to notice
the Allkaruen/Pterodaustro connection. If others preceded me, please let me know so I can congratulate and confirm them.

Everyone, including Codorniu et al., is looking for
that one transitional taxon, that ‘missing link’ between long-tailed pterosaurs and short-tailed pterosaurs. Andres, Clark and Xu 2014 failed when they mistook small parts of a skinny dorygnathid for a much smaller pterodactyloid. Lü et al. 2010 failed when they added Darwinopterus to a small gamut cladogram. Codorniú et al. failed when they promoted Allkaruen to that position. The authority to state that these PhDs failed comes from a large gamut cladogram, the LPT, that tests their short taxon lists with a much larger taxon list. The LPT documents four appearances of pterodactyloid-grade clades and so will competing studies when they expand their lists, create reconstructions and have a third party certify their scores are correct.

Ironically, no one’s looking for
that one transitional taxon, that ‘missing link’ between pre-volant pterosaur ancestors and basal pterosaurs. Do you wonder why that is? I can only suppose no one wants to confirm the published work of an amateur from 17 years ago (Peters 2000). There’s no reward in it for PhDs. No one wants to admit they were wrong and needlessly parochial for 17 years.

References
Andres, B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology. 24: 1011–6.
Codorniú L, Carabajal AP, Pol D, Unwin D and Rauhut OWM 2016.
 A Jurassic pterosaur from Patagonia. and the origin of the pterodactyloid neurocranium. PeerJ 4:e2311; DOI 10.7717/peerj.2311
Lü J-C, Gao C-L, Meng Q-J, Liu J-Y, Ji Q 2006. On the Systematic Position of Eosipterus yangi Ji et Ji, 1997 among Pterodactyloids. Acta Geologicia Sinica 80(5):643-646.
Lü J, Unwin D, Jin X, Liu Y, Ji Q 2010. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceeding of the Royal Society B 273:383389.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. In:Buffetaut E, Mazin J-M, eds. Evolution and Paleobiology of Pterosaurs, vol. 217. London: Geological Society, Special Publications, 139190.

wiki/Allkaruen

Another look at a possible pterosaur wingtip ungual

Figure 1. The Yale specimen of Rhamphorhynchus phyllurus with preserved wingtip ungual highlighted. See figure 2 for closeup.

Figure 1. The Yale specimen of Rhamphorhynchus phyllurus with preserved wingtip ungual highlighted. See figure 2 for closeup.

The Yale specimen of Rhamphorhynchus phyllurus (Figs. 1, 2; VP 1001778) has one painted wing tip and one that may include another wingtip ungual.

Figure 2. Closeup of Rhamphorhynchus phyllurus in figure 1 focusing on the preserved wingtip ungual.

Figure 2. Closeup of Rhamphorhynchus phyllurus in figure 1 focusing on the preserved wingtip ungual. Was this carved in? Or is it real? Note the cylindrical tip of the penultimate wing phalanx (m4.4). The wingtip was buried deep within the matrix and had to be exposed.

The wingtip
was buried deep within the matrix and had to be exposed. So the question is: was it carved? Or is it real? If it was carved, why was it carved? Traditionally pterosaurs are not supposed to have wing tip unguals, but I’ve found them in several specimens.

You might remember
we looked at this wing tip earlier with a different provided image. The present one appears to offer more clues.

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.