The Beauty and Benefit of Crushed Fossils

This photo an 16th century galleon in the Baltic reminded me that similar crushed fossils sometimes provide more data at a glance than first meets the eye.

Figure 1. A sunken flattened ship is like a sunken flattened pterosaur fossil. Here the lateral view is easy to see and the dorsal view can be reconstructed from the loose planks.

Figure 1. A sunken flattened ship is like a sunken flattened pterosaur fossil. Here the lateral view is easy to see and the dorsal view can be reconstructed from the loose planks.

Here is the R156 specimen of Dorygnathus about to eat a displaced femur.

Figure 2. The R 156 (Uppsala) specimen of Dorygnathus. Crushed and scattered like a sunken galleon.

Figure 2. The R 156 (Uppsala) specimen of Dorygnathus. Crushed and scattered like a sunken galleon.

And here is how the displaced ‘planks’ (in this case, phalanges) can get put back together using DGS (digital graphic segregation) techniques: colorizing the bones then moving the colors into a reconstruction, checking with PILs. A little intuition and experience also helps.

Figure 3. The disarticulate pes of Dorygnathus here reconstructed using DS into a complete pes.

Figure 3. The disarticulate pes of Dorygnathus here reconstructed using DS into a complete pes. Wondering now whether or not those metatarsals were splayed or appressed when walking. 

References
Padian K 2009. The Early Jurassic Pterosaur Dorygnathus banthenis (Theodori, 1830) and The Early Jurassic Pterosaur Campylognathoides Strand, 1928, Special Papers in Paleontology 80, Blackwell ISBN 9781405192248

New Jianchangnathus?

Figure 1. The new Jianchangnathus(?) compared to the holotype. The new one has a quite broad skull and an antorbital fenestra that extends below the orbit, unlike the holotype.

Figure 1. The new Jianchangnathus(?) compared to the holotype. The new one has a quite broad cranium and an antorbital fenestra that extends below the orbit, unlike the holotype, but like Scaphognathus. Other differences are just as obvious. 

A new pterosaur PMOL-AP00028 (Zhou 2014) has been attributed to Jianchangnathus IVPP V 16866, Cheng et al. 2012), but that does not seem warranted in this case. The comparable traits are not close matches. Zhou did not make graphic comparisons of the holotype and referred specimen. Rather the two specimens were combined then compared to other rhamph-grade taxa as illustrated by Wellnhofer (1991 and earlier). I think a step or two was skipped in Zhou 2014.

Based on the orbit overhanging the antorbital fenestra, the closer match might be to Scaphognathus itself, which was close to the size of the referred specimen.

References
Cheng X, Wang X-L, Jiang S-X and Kellner AWA 2012. A new scaphognathid pterosaur from western Liaoning, China. Historical Biology iFirst article available online 29 Nov 2011, 1-11. doi:10.1080/08912963.2011.635423
Zhou C-F 2014. Cranial morphology of a Scaphognathus-like pterosaur, Jianchangnathus robustus, based on a new fossil from the Tiaojishan Formation of western Liaoning, China. Journal of Vertebrate Paleontology 34(3):597-605.

wiki/Jianchangnathus

New basal pterodactyloid(?) Kryptodrakon = Sericipterus, a dorygnathid

The big news this morning:
Andres, Clark and Xu (2014) have claimed to discover the earliest known pterodactyloid (Middle/Late Jurassic, Shishugou Formation in Xinjiang, China).They wrote: “We report here the earliest pterosaur with the diagnostic elongate metacarpus of the Pterodactyloidea, Kryptodrakon progenitor, gen. et sp. nov., from the terrestrial Middle-Upper Jurassic boundary of Northwest China. Phylogenetic analysis confirms this species as the basalmost pterodactyloid.”

Andres reported, “In paleontology, we love to find the earliest members of any group because we can look at them and figure out what they had that made the group so successful.” 

If it is one, it’s a big one!
Wingspan estimates are over a meter.

That big size is the red flag
Of course, this flies in the face of the large pterosaur tree, which recovered four origins for pterodactyloid-grade pterosaurs at about this same time, and they were all tiny. Andres, Clark and Xu did not include these tiny pterosaurs in their phylogenetic analysis.

Figure 1. The bits and pieces of Kryptodrakon assembled into a Pterodactylus bauplan, from Andres, Clark and Xu 2014.

Figure 1. The bits and pieces of Kryptodrakon assembled into a Pterodactylus bauplan, from Andres, Clark and Xu 2014.

It’s always difficult to reassemble bits and pieces,
but not impossible. Andres, Clark and Xu did that above (Fig. 1), using a small Pterodactylus as their bauplan or blueprint.

There’s an alternate bauplan available
and it’s also from the same Shishugou Formation. Sericipterus is a very large and gracile dorygnathid (Fig. 2). When you put the bones of Krypodrakon on top of the bauplan for Sericipterus you find a good match.

Figure 2. The bone bits of Kryptodrakon placed on the bauplan of the giant dorygnathid, Sericipeterus, also from the Shishugou Formation. There's a good match here.

Figure 2. Here the bone bits of Kryptodrakon are placed on the bauplan of the giant dorygnathid, Sericipeterus, also from the Shishugou Formation. There’s a good match here. Perhaps Kryptodrakon is a junior synonym for Sericipterus, filling in some of its missing pieces.

And suddenly that “long metacarpus” is not so long anymore. Notably, Sericipterus had gracile wing bones, and that proved confusing to Andres, Clark and Xu. “Thinner” can sometimes be confused with “longer” unless you know what the bauplan is.

But wait, there’s more.
Compare the metacarpus of Kryptodrakon with its dorsal rib and the metacarpus doesn’t look so long anymore. The same holds for the distal carpal, scapula, humerus and wing joint scraps. They’re all too big for that metacarpus to be “elongate.”

A more parsimonious solution
Kryptodrakon and Seripterus are both from the same formation. They are the same size, and their bones have the same shape (so far as can be told from available scraps). We also know from a larger phylogenetic analysis that includes tiny pterosaurs that basal pterodactyloid-grade pterosaurs were all tiny and Kryptodrakon was big.

Therefore,
the more parsimonious solution is to consider Kryptodrakon a junior synonym for Sericipterus, a giant dorygnathid, not a pterodactyloid.

One more thing
Andres, Clark and Xu were also the discoverers and authors of Sercipterus, the only other pterosaur found in the Shishugou Formation.

Sorry to throw cold water on this.
But testing for parsimony is good Science.

References
Andres B, Clark JM and Xu X 2010.A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.
Andres B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology (advance online publication)
DOI: http://dx.doi.org/10.1016/j.cub.2014.03.030

Read more: Science_News

The Sericipterus mandible reconstructed – new insights using Photoshop

I love it when this happens.
I made a mistake here earlier today, and within just a few hours, I am able to correct it. So what you are about to read here has been thoroughly rewritten to reflect the latest thinking.

Earlier I misidentified what looked like a too gracile mandible (relative to the other skull parts) on the pterosaur, Sercipterus (Figs. 1-3), as a tibia and fibula. Here is the illustration in which I made the mistake (Fig. 1). And made a further mistake by calling out the original interpretation as an error.

Figure 1. From Andres et al. 2010, where they misidentify a tibia/fibula and call it a mandible with surangular.

Figure 1. Click to enlarge. From Andres et al. 2010, where they identify a mandible and surangular. I thought it odd that it would be preserve narrow edge up, and where are the teeth or their alveoli? But now i see the reason for this. Read on.

At the time I overlooked the left mandible. It’s easy to do. There’s not much that makes it look like a mandible. The back half is all that is preserved. The left mandible appears to be a little deeper, which it needs to be according to phylogenetic bracketing.

This is the key. 
Allthough the fossil had been thoroughly stirred during preservation so that nothing is where it was in the living pterosaur, there are two bones that are indeed in their original configuration: the two posterior mandibles (Fig. 2, in pink). How can this be??

Figure 2. When you use your imagination, and a little Photoshop, you can retire the front of the mandible. What we're seeing is the ventral view, so no teeth are visible. The reason why the mandibles remain in their original configuration is the front of the fused mandibles, now vanished. And that's why the right mandible is preserved narrow end up.

Figure 2. When you use your imagination, and a little Photoshop, you can restore the front of the mandible. What we’re seeing here is the ventral view, so no teeth are visible. The reason why the posterior mandibles remain in their original edge-on configuration is due to the front of the fused mandibles, now vanished. The entire mandible was originally preserved in its flattest plane. And that’s why the right mandible remains narrow end up.

Restoration of the missing parts clears up all the confusion.
When you extend the lines of the posterior mandible, the anterior portion becomes plainly visible. Now we have a mandible that is the proper length for the skull parts (actually it elongates the earlier restoration of the skull and suggests a larger antorbital fenestra than in other dorygnathids, Fig. 3). And now the narrow mandible makes sense because it is not preserved in lateral view.

Figure 3. New reconstruction of Sericipterus with restored mandible in lateral view based on the related MBR 1920 specimen, in color at right.

Figure 3. New reconstruction of Sericipterus with restored mandible in lateral view based on the related MBR 1920 specimen, in color at right.

Colleague [name deleted] was kind enough to drop a note on this (see below) that prompted a review of the situation. Later Mike wrote, “Sometimes it is better to trust people who have spent many hours with the specimen in front of them and read the descriptions.”

That’s a common notion,
but that’s not the thought you should take-away from this exercise.

Science doesn’t work on trust.
It works on testing. Having never seen a mandible preserved edge-on in the matrix, without obvious alveoli and too gracile for the skull, I sought another explanation for the questionable portion of the fossil. The tibia/fibula seemed to be a good fit.

But I was wrong. The mandible was not preserved edge-on, but flattened along its widest dimensions, like most fossils are. Then the anterior half of the fused mandible was lost leaving the posterior parts edge-on. Now it makes sense.

It would have helped if the above restoration was made prior to publication. I’m sure you can see how well it illustrates the situation here. Making mistakes is one way to shed new light on a problem. I never would have arrived at this solution and explanation had I merely trusted the original authors.

When something doesn’t make sense, keep working on it until it does makes sense.

It’s a process. And I’m always glad to accept any help that is offered. Getting it right is the ultimate goal.

References
Andres B, Clark JM and Xing X 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.

Focus on Angustinaripterus – transitional between Dorygnathus and Ctenochasma

Angustinaripterus (Fig. 1) has been difficult to classify for other pterosaur paleontologists. Here in the large pterosaur tree the reason becomes quite evident. Add a few taxa and Angustinaripterus become a transitional taxon between the more primitive Dorygnathus (R154) and the more derived Gnathosaurus and Ctenochasma.

Figure 1. Angustinaripterus as a transitional taxon between Dorygnathus and Gnathosaurus.

Figure 1. Angustinaripterus as a transitional taxon between Dorygnathus and Gnathosaurus. Seems pretty obvious. Phylogenetic analysis confirms.

This possibility flips out traditional pterosaurologists who have pinned their hopes on Darwinopterus, which doesn’t look much like either Ctenochasma or Dorygnathus.

But that’s not all
Here (Fig. 2) are the many other specimens that smooth the evolutionary transition, as we noted before. Here they are. And many of them are tiny.

Figure 2. The same sequence with the addition of Dorygnathus purdonti and four tiny pterosaurs variously misassigned to Pterodactylus and Ctneochasma.

Figure 2. The same sequence with the addition of Dorygnathus purdonti and four tiny pterosaurs variously misassigned to Pterodactylus and Ctneochasma. Black illustrations are to scale. Gray figures are enlarged to show detail.

Angustinaripterus is the reason why I delved deeper into pterosaur phylogeny than anyone has done before. At first glance it’s clearly something not quite Dorygnathus and not quite Gnathosaurus or Ctenochasma.

The next step after Angustinaripterus was to add in some…

Tiny pterosaurs
This (Fig. 2) is only one sequence of many in which tiny adult pterosaurs are transitional between larger forms, both more primitive and more derived. At first glance, and according to tradition, these tiny pterosaurs are only juveniles or hatchlings, which makes perfect sense—until you add them to your matrix—and you realize juvenile pterosaurs of other types are virtual copies of adults. So there was no allometric growth after hatching, but chiefly isometric growth.

But there’s an important clue here staring you right in the face: Note how the tiny pterosaurs are ALL the same size. As it turns out, this is the minimum size at which pterosaurs could fly, evidently, as we find no smaller pterosaurs in the fossil record. Smaller pterosaurs, all juveniles, must have been living in damper environments and probably not flying. Some hatchlings, like the IVPP embryo, were as large as these adult pterosaurs (Fig. 2) and other adult tiny pterosaurs, so they could fly immediately. 

References
He X-L, Yang D-H and Su C-K 1983. A New Pterosaur from the Middle Jurassic of Dashanpu, Zigong, Sichuan. Journal of the Chengdu College of Geology supplement 1: 27-33.

wiki/Angustinaripterus

Variation within Dorygnathus – part 2

Kevin Padian (2008) on Dorygnathus banthensis represents the latest traditional thinking on this genus and species. We’re expanding on that with multiple reconstructions and a phylogenetic analysis, both lacking previously. Yesterday was part 1.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternum in all cases.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternal complex, smaller antorbital fenestra, longer m4.1  and shorter neck in all cases. The other distinctions are less obvious.

Often confused with or mistakenly related to Rhamphorhynchus
Dorygnathus
 (Fig. 1) and Rhamphorhynchus both shared big procumbent teeth by convergence. Whereas Rhamphorhynchus is known from several sizes (falsely considered ontogenetic by those who have not performed a phylogenetic analysis on clade members), Dorygnathus is not well known for size differences (Fig. 2), but there are some small ones and large ones.

Sericipterus (Andres et al. 2010, Fig. 2) is larger than the others, but it is not considered congeneric. Andres et al. (2010) considered it closest to Harpactognathus and Angustinaripterus (Fig. 2), both pre-ctenochasmatid dorygnathids. Their tree found these three taxa and Cacibupteryx to be derived from a sister to Dorygnathus, which is duplicated in the large pterosaur tree, only with more intervening and related taxa.

Looking for “juveniles,” but didn’t find any
Curious, I wondered if the small “Hauff” specimen would nest with one of the other larger specimens and so be considered a possible juvenile. So I ran the analysis. Instead, the Hauff specimen nested at the base of the clade, derived from a sister to the equally small Sordes (Fig. 1). This is not unexpected, but follows size patterns seen in most, if not all, major pterosaur clades with smaller specimens at the bases of distinct clades and genera. This went unnoticed in Dorygnathus until now.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you're a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangopterus. So Dorygnathia survived to the Maastrichtian.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you’re a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangnathus. So Dorygnathia survived to the Maastrichtian. A small one, the Hauff specimen, is basal. There is also a clade leading to a large Sericepterus that did not lead to other clades. The variety here is comparable to the Rhamphorhynchus clade.

SMNS 558866 is also small (Fig. 1), but nests between two larger specimens. While sharing many traits with all other Dorygnathus specimens, it appears to have a unique morphology, so is not a juvenile of the R156 specimen or Cacibupteryx.

So no juveniles here!! (Same as in Rhamphorhynchus, they’re growing up in damp leaf litter far from ancient Geman seas). I would have liked to have discovered some juveniles here, but you have to let the data do the talking.

To lump? Or to split?
The Dorygnathus clade suffers from the same nomenclature problem that other pterosaur clades suffer from. Several professionally named “Dorygnathus” are phylogenetically separated from one another by more recently named novel genera. No prior phylogenetic analysis including more than one Dorygnathus was ever attempted before. That’s the main problem. As you can see, there is variety within this clade that was previously overlooked.

There is no more and no less variation here in Dorygnathus than in the present Pteranodon, Pterodactylus, Germanodactylus, Rhamphorhynchus, Eudimorphodon and other wastebasket taxa. Someday a grand poobah will straighten this all out for us and have his authority respected. I don’t care if the lumpers win or the splitters win, but the tree has to be acknowledged agreed upon before we get down to naming genera again. It’s getting very confusing out there.

Tomorrow we’ll talk about Dorygnathus’ most embarrassing trait, that tiny sternal complex.

References
Andres B, Clark, JM and Xing X 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs’, Journal of Vertebrate Paleontology, 30: 1, 163-187.
Padian K 2008. The early Jurassic pterosaur Dorygnathus banthensis (Theodori, 1830). Special papers in palaeontology 80: 64 pp.

Variation within Dorygnathus – part 1

Kevin Padian (2008) on Dorygnathus banthensis represents the latest traditional thinking on this genus and species. Unfortunately he did not reconstruct more than one specimen (Fig.1) and he did not employ phylogenetic analysis neither between specimens nor between other pterosaurs. Those shortcomings are rectified here. This post was inspired by the addition of three new Dorygnathus specimens to the cladogram (Fig. 2 in color).

Padian's (2008) version of Dorygnathus taking off. This is a freehand sketch, not a tracing of bones.

Figure 1. Padian’s (2008) version of Dorygnathus taking off. This is a freehand sketch, not a tracing of bones (as in Figs. 2, 3). Padian did not attempt to reconstruct more than one Dorygnathus to test the supposition that there are over 30 specimens of this one genus and species. Nor did he attempt a phylogenetic analysis. Reconstructions (Fig. 2) illuminate the subtle and not so subtle variations. Padian’s bipedal pterosaur appears to be in an attack mode. I’d like to see him draw Dorygnathus in a common pose of balance.

From the Padian abstract (abridged here):  
“Over 30 skeletons and dozens of isolated bones of the Liassic pterosaur Dorygnathus have been recovered from the Early Jurassic (Toarcian) of Baden–Württemberg and Lower Saxony in Germany, and from Nancy, France. All but one specimen have been assigned to the species D. banthensis. Dorygnathus is most closely related to Rhamphorhynchus and the Pterodactyloidea.”

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you're a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangopterus. So Dorygnathia survived to the Maastrichtian.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you’re a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangnathus. So Dorygnathia descendants survived  into the Maastrichtian. A small one, the Hauff specimen, is basal. There is also a clade leading to a large Sericepterus that did not lead to other clades, but became extinct. The variety here is comparable to the Rhamphorhynchus clade.

Maybe not…
Reconstructions of several Dorygnathus specimens (Fig. 1) reveal an overlooked variety in this genus that does not become readily apparent until accurate tracings and reconstructions are made. These specimens do not appear to be conspecific, confirmed by phylogenetic analysis. Each has at least a few distinct traits. While most specimens were about the same size, each had a distinct morphology with longer and shorter skulls, different sized fingers, distinct sternal complex and pelvis shapes and distinct pedal proportions.

Descent and descendants
According to the large pterosaur tree, Dorygnathus descended from a sister to Sordes and Changchengopterus, both smaller specimens.

To Padian’s point: Dorygnathus is a key taxon at the base of two pterodactyloid-grade clades: ctenochasmatidae (which retained long teeth) and azhdarchidae (which did not). Dorygnathus is also a key taxon at the base of Jianchangnathus + Pterorynchus + Darwinopteridae and Scaphognathus (which is basal to all remaining pterodactyloid-grade pterosaurs) and these also had smaller teeth. Padian, unfortunately, did not see the specifics, but reported very broad generalizations regarding pterosaur relations.

Despite appearances, Dorygnathus is not so much related to Rhamphorhynchus, but both developed long procumbent teeth by convergence and share a last common ancestor near basal Campylognathoides and Eudimorphodon.

From the Padian text:
“It appears that Dorygnathus is most closely related to Scaphognathus and Rhamphorhynchus, though without some of the synapomorphies that appear to ally the latter genus to the Pterodactyloidea (such as the lower, longer snout, the anterior displacement of the jaw joint to beneath the midpoint of the orbit, the more steeply inclined quadrate, the reduction of the lower temporal fenestra, the elongation of the first wing-phalanx, and the partial reduction of the fifth toe).”

So, Padian is going on appearances here, not analysis
[Actually many pterosaurs, including the SMNS 50164 specimen of Dorygnathus had a lower, longer snout along with the anterior displacement of the jaw joint. According to the large pterosaur tree Rhamphorhynchus inherited its long first wing phalanx from Campylognathoides and most pterodactyloid-grade pterosaurs and Dorygnathus do not share this trait. Likewise the partial reduction of the fifth toe in Rhamphorhynchus was inherited from Campylognathoides.] Dorygnathus retained an elongated pedal digit 5 with a bent p5.2.

From the Padian text:
“Dorygnathus appears to be one of the closest genera to Rhamphorhynchus and, hence, to the Pterodactyloidea (a conclusion independently reached by Unwin 2003a). They share a long mandibular symphysis that is toothless at its anterior end, large anterior teeth strongly inclined forward and outward, nares more reduced and located more posteriorly and higher on the skull, reduced antorbital opening, and jugal lacking a posterior process along the base of the skull.”

[Again, in this age of phylogenetic analysis, basing relationships on “appearance” is to be avoided.] Padian errors when he reports that all Pterodactyloidea has a long mandibular symphysis that is toothless anteriorly disregarding exceptions here, here and here. The nares are also reduced in the non pterodactyloids, Pterorhynchus and Darwinopterus. Pterodactyloids do not have a reduced antorbital opening. Some Dorygnathus and Rhamphorhynchus share this trait, but other Dorygnathus evolve a larger antorbital fenestra. Neither clades are 100% without a jugal posterior process.

From the Padian text:
Dorygnathus shares other features with Scaphognathus but most appear to be plesiomorphies for the lineage. I conclude that Dorygnathus is a member of the main stem of pterosaur evolution leading to the Pterodactyloidea, and is the closest representative of this main lineage in the Early Jurassic.Both Campylognathoides and Dimorphodon, the two other known Liassic genera, are too different and specialized to be as closely related to this main stem of pterosaur evolution; they are important side-branches with roots in the Late Triassic forms.”

[Giving credit where credit is due (even though the current large pterosaur tree topology specified by Peters 2007 predates this), Padian correctly connects Dorygnathus to pterodactyloids, but he has no idea which ones or through which specimens. He simply notes [correctly] that Dorygnathus is a better Liassic candidate than the other two Liassic candidates, Campylognathoides and Dimorphodon.]

It's better to trace bones accurately than to freehand reconstructions. Moreover, the quadrupedal pose Padian promotes has several errors (fingers not lateral, hands in front of shoulders, humerus over abducted).

Figure 3. It’s better to trace bones accurately than to freehand reconstructions. Moreover, the quadrupedal pose Padian promotes has several errors (fingers not lateral, hands in front of shoulders, humerus over abducted). Currently no pterosaur tracks match Dorygnathus feet. The huge manual claws argue against a quadrupedal configuration. Padian, once the champion of bipedal locomotion in pterosaurs, must not have had much evidence to stand on if he has fallen so far the other way.

From the Padian caption (Figure 3):
Dorygnathus banthensis; reconstruction of the skeleton in a hypothetical quadrupedal pose. In this position the left humerus has reached the limit of forward protraction and rotation; retraction of the limb would have been slight, with minimal force. The pace length of the hindlimbs would not have been so limited and would have been much greater than that of the forelimbs. This suggests that the forelimbs could have served as little more than supports for the front end of the body, if they were necesary at all. Note also the forward slope of the dorsal column in this position.”

[Actually, in Padian’s tipped over pose (Fig. 3) the forelimbs would have been essential for support. However, in the Peters pose (Fig. 3, color) the forelimbs could be elevated or implanted without changing the center of balance over the toes. The Padian skull is not an accurate representation of the Vienna specimen and his pedal digit 5 is way too small, the unfortunate results of ‘eyeballing’ it.]

More tomorrow and the next day when Dorygnathus gets really interesting

References
Padian K 2008. The early Jurassic pterosaur Dorygnathus banthensis (Theodori, 1830). Special papers in palaeontology 80: 64 pp.

Nicknamed “Rhamphodactylus” – Is it a Transitional Pterosaur?

Last year Rauhut (2012) published on a new pterosaur, BSPG 2011 I 133, now being nicknamed, “Rhamphodactylus,” in honor of its purported transitional status between rhamphorhynchoids and pterodactyloids.

We learned earlier than neither term is monophyletic.

Rhamphorhychoids, as everyone knows, are simply basal pterosaurs and they “stop” being rhamphorhynchoids when some evolve pterodactyloid traits.

The pterodactyloid grade had four origins, two out of Dorygnathus and two out of Scaphognathus (itself a dorygnathid).

Darwinopterus and kin developed several pterodactyloid traits, but they were a dead end, producing no known descendants in the Cretaceous, according to the results of the large pterosaur tree.

Figure 1. Rhamphodactylus in situ, colors applied to identify bones. See reconstruction. Scale bar is 3 cm. The short tail (closeup in figure 5) is just to the left of the scale bars.

Figure 1. Rhamphodactylus in situ, colors applied to identify bones. See reconstruction. Scale bar is 3 cm. The short tail (closeup in figure 5) is just to the left of the scale bars.

Rauhut (2012) mentions the well known traits of the pterodactyloid grade:

  1. short tail
  2. coalesced naris/antorbital fenestra
  3. longer neck and
  4. longer metacarpal.

He lists Darwinopterus (Middle Jurassic, China) and another South American form based on scraps as pterosaur transitional taxa. To these he adds the new specimen (Figs. 1-5). No phylogenetic analysis was performed for the short paper.

Figure 2. Rhamphodactylus skull. Note the large antorbital fenestra. Maxilla

Figure 2. Rhamphodactylus skull. Note the large antorbital fenestra. Maxilla

It would be certainly tempting
to consider “Rhamphodactylus” a transitional taxon, but we already have four well-established transitional series, all made up of tiny taxa. The fact that traditional pterosaur workers continue to refuse to add tiny pterosaurs to their analyses means they will never know the path or mechanism for pterosaur evolution. “Rhamphodactylus” is on the small side (Fig. 6). So, perhaps it will open the door for other tiny pterosaurs to be studied and recognized as tiny adults.

Despite hopes
The new taxon, it turns out, merely fills the gap between tiny TM 10341 and Beipiaopterus + CM  11426 (Fig. 6), so all three are pterodactyloid-grade pterosaurs. This is a dorygnathid-like skull, but the teeth are reduced, a characteristic of this clade that ultimately produced toothless azhdarchids. Moving “Rhamphodactylus” to the darwinopterids adds 11 to 18 steps. Moving “Rhamphodactylus” one node closer to Dorygnathus adds 4 steps.

Rhamphodactylus manus

Figure 3. Rhamphodactylus manus

Rauhut (2012) notes “Rhamphodactylus” (Upper Jurassic) has a metacarpal length exactly between the statistical cloud of rhamphs and pterodacs. For such details it’s worthwhile to check out accurate reconstructions of its sister taxa (Fig. 6) both of which have the shortest metacarpals of all pterodactyloid-grade pterosaurs. Other transitional taxa all had relatively longer metacarpals.

Figure 4. Rhamphodactylus reconstructed. Yes, there's a possible skull at 1/8 the size of the adult specimen near the tail.

Figure 4. Rhamphodactylus reconstructed. Yes, there’s a possible skull at 1/8 the size of the adult specimen near the tail.

Reconstruction of “Rhamphodactylus.”
The study of roadkill specimens benefits greatly from a reconstruction (Fig. 4), but rarely occurs. “Rhamphodactylus” retains the maxillary notch present in Dorygnathus and TM 10341 and provides clues as to the morphology of the unknown skull of Beipiaopterus. Reconstructing the foot is also highly diagnostic.

Figure 5. Abbreviated tail of "Rhamphodactylus" along with a possible aborted embryo at 1/8 the size of the adult.

Figure 5. Abbreviated tail of “Rhamphodactylus” along with a possible aborted embryo at 1/8 the size of the adult. Since the last caudal retains a chevron, my guess  is the tail continues on in reduced form, curling right (dashed green line) then back toward the base where it terminates in loose strands (upper right). The rest of the tail is either lost or buried or both.

Is BSPG 2011 I 133 a mother?
I would encourage the preparators of “Rhamphorhynchus” to be especially vigilante around the tail as there appears to be a possible embryo skull there, aborted during taphonomy. Then again, those indications could represent preparation marks.

Figure 5. Click to enlarge. Rhamphodactylus and kin.  Dorygnathus SMNS 50164, TM 10341, Rhamphodactylus, Beipiaopterus and CM 11426 to scale

Figure 6. Click to enlarge. Rhamphodactylus and kin. Left to righ: Dorygnathus SMNS 50164, TM 10341, Rhamphodactylus, Beipiaopterus and CM 11426 to scale.

According to the large pterosaur tree, “Rhamphodactylus” nests close to Dorygnathus (SMNS 50164 specimen) between TM 10341 and Bepiaopterus and CM 11426. It is certainly a transitional taxon, as all of these taxa are, but it represents the size increase portion of the lineage.

Pterodactyloid-grade traits were already present in tiny TM 10341, which has been known for decades, but has been largely ignored and considered a juvenile or hatchling. TM 10341 is closer to the transitional point. lt has a shorter neck, shorter metacarpus and shorter skull. This is the lineage (Fig. 6) that ultimately produced flightless waders and giant azhdarchids.

The other dorygnathid lineage emphasized the teeth and produced ctenochasmatids.

The two scaphognathid clades reduced the rake-like teeth and produced cycnorhamphids + ornithocheirids on one branch and pterodactylids + germanodactylids and their larger descendants on the other.

It’s nice to celebrate the finding of new transitional taxa,
but let’s remember the real transitional taxa have been known for decades, if not centuries. Let’s not ignore them any longer. Traditional paleontologists won’t appreciate this news. It exposes their oversights and the discoveries that should have been theirs’ but now have fallen into the hands of amateurs. Discoveries are celebrated. Requests for speaking engagements and IMAX appearances can turn on a good run of discoveries.

On the other hand,
being embarrassed in paleontology by a run of false discoveries often turns into a good ole’ Amish shunning, or “Meidung”, the German word for avoidance. Today the only problem with Meidung in professional paleontology is the purposeful avoidance of good data and more parsimonious results based on larger inclusion sets. Pterosaur authors like Hone, Unwin and Witton who avoid looking at tiny pterosaurs and fenestrasaurs in phylogenetic analyses are running the risk here and I encourage them to take their blinders off.

References
Rauhut OWM 2012. Ein “Rhamphodactylus” aus der Mörnsheim-Formation von Mühlheim. Freunde der Bayerischen Staatssammlung für Paläontologie und Historische Geologie e.V., Jahresbericht und Mitteilungen 01/2012; 40:69-74.  online here.

News story in German

Dorygnathus – where are the postorbital bones? DGS to the rescue.

My first encounter with the UUPM R156 (Uppsala Museum, Sweden) Dorygnathus was in Wellnhofer (1991), the famous pterosaur encyclopedia. The image was small and produced with halftone dots. Nevertheless I produced a reconstruction from it and I used the fuzzy data in the large pterosaur tree.

The resolution question.
There are a whole raft of pterosaur workers who dismiss such efforts gleaned from photographs, both of poor quality and excellent. Some photographic data comes from publications. Other data comes from photographs I’ve taken on various trips to visit the specimens. Sometimes those photos come in handy long after the trip is over as new insights come in randomly.

Now let’s draw a parallel. There was a time, before the advent of the Hubble telescope and the Voyager and other flyby satellites, when the best images we could get of the planets came form Earth-bound telescopes beneath an ocean of atmosphere. Fuzzy is the best way to describe them. The broiling atmosphere was the problem. Even in photos from the largest telescopes there’s not a a lot of resolution. Then, after 1990, Hubble images provided a magnitude leap in resolution because they were taken far above the atmosphere.

Figure 1. The planet Jupiter as seen from above the atmosphere (Hubble) and below (Hale). Having a poor resolution photo did not impede astronomers from gathering data on Jupiter.

Figure 1. The planet Jupiter as seen from above the atmosphere (Hubble) and below (Hale). Having a poor resolution photo did not impede astronomers from gathering data on Jupiter.

But did that stop astronomers from studying Jupiter?  No. You take what you’re given. And when you’re given better data you refine your hypotheses. What you don’t do is denigrate others for gathering data using the best available data, fuzzy though it may be. That is what the opposing camp of traditional pterosaur experts (Naish, Witton, Bennett, Hone, Unwin) do. Those are the experts you’ll recall, who are most responsible for disfiguring pterosaurs. They are still hoping that pterosaurs had deep chord wing membranes, fingers that faced palms forward in flight, babies that did not look like grownups, strong sexual dimorphism, eggs that were buried under rotting vegetation, a cruropatagium controlled by the lateral digits and, perhaps worst of all, they still have no idea what pterosaurs are despite being given the answer some 12 years ago (Peters 2000). They could have discovered what pterosaurs are, just by testing, looking and comparing. But they refuse to. 

Getting back to Dorygnathus R156
The skull of the R156 specimen (Fig. 2) appeared online and it offered better resolution than the Wellnhofer (1991) print. So I applied DGS to it and discovered several previously “missing” bones. None of these have been documented yet, as far as I know. Padian (2009) did not illustrate this specimen in his recent treatise on Dorygnathus, but described it nevertheless. Padian (2009) reported that Wiman (1925) wrote a detailed paper on the specimen.

Figure 2. Here is the R156 specimen of Dorygnathus. Can you find the postorbital. pterygoid and squamosal?

Figure 2. Click to enlarge. Here is the R156 specimen of Dorygnathus. It looks like a complete skull, but can you find the postorbital. pterygoid and squamosal? Image has been corrected for perspective from the original posted photo. That’s the left femur in the teeth.

Padian (2009) wrote that Wiman (1925) noted, “the bones of the left side of the skull behind the premaxilla are missing, so that one sees the posterior part of the skull from inside the right side.” Padian also considered the squamosal missing but made few comments about the skull other than the teeth and jaw symphysis, the most easily seen elements. He did not comment on the palate or occiput elements, which are more difficult to determine.

. Click to enlarge. Digital Graphic Segregation applied to the skull revealing the location of the displaced postorbital and palatal elements.

Figure 3. Click to enlarge. Digital Graphic Segregation applied to the skull revealing the location of the displaced postorbital and palatal elements. Note much of the left maxilla is missing, revealing the right maxilla in medial view. Look closely to see the replacement tooth coming up laterally on the longest dentary tooth.

DGS Step-by-step
Digital Graphic Segregation helps one understand crushed fossils by removing areas of chaos and segregating bones by color and layer. Coloring the easy bones first ultimately reveals the difficult ones. And that’s the beauty of it. Later, making a reconstruction of the elements lifted and placed digitally, confirms the fit of the rest.

The parietal lateral elements were broken off and slightly displaced. The postorbital lay inside the jugal (Fig. 3). I would be surprised if the palatal elements have ever been identified. They are currently folded up in the parasagittal plane. The major elements of the occiput are probably washed away along with the left side of the skull.

Dorygnathus R156 reconstructed in three views. Elements from the insitu image were lifted intact and reassembled here in the second phase of DGS. A reconstruction confirms the identification of the elements as the puzzle pieces fit back together in patterns that resemble sister specimens.

Figure 4. Dorygnathus R156 reconstructed in three views. Elements from the insitu image were lifted intact and reassembled here in the second phase of DGS. A reconstruction confirms the identification of the elements as the puzzle pieces fit back together in patterns that resemble sister specimens. There were probably more dentary teeth, but the present view (Fig. 3), taken from slightly below. does not reveal them.

Phylogenetic analysis
The original reconstruction was refined by the new reconstruction (Fig. 4), but only two or three traits changed scores in the large pterosaur tree. The result of these rescorings nested R156 with Sericipterus, which it nested next to previously.

Doryganthus UUPM R156 revised with new data coming from the online image in high resolution of the skull and cervicals.

Figure 5. Doryganthus UUPM R156 revised with new data coming from the online image in high resolution of the skull and cervicals. Science marches on.

The nearly parallel pterygoids are atypical for pterosaurs in general, but become even more parallel in ctenochasmatids. R156 is in the lineage of ctenochasmatids according to the large pterosaur tree, something that should be obvious from its similarly protruding teeth. A while back those teeth were the first clues I had of a possible direct ancestry with ctenochasmatids. Later, by adding taxa, I realized that the tiny pre-ctenochasmatids transitioned larger forms like Angustinaripterus to Ctenochasma.

The Vienna specimen of Dorygnathus portrayed in Wiman 1925, a study of the R156 Uppsala specimen.

Figure 6. The Vienna specimen of Dorygnathus portrayed in Wiman 1925, which, ironically, is a study of the R156 Uppsala specimen, not the Vienna specimen shown here. The R156 specimen was not illustrated by either Wiman or Padian.

Wiman (1925) likewise did not figure the R156 skull
Like Padian (2009), Wiman (1925) did not illustrated the the R156 skull. Instead Wiman employed the Vienna specimen skull, after Arthaber. Compared to figure 3, several of the suture differ here, perhaps attributable to a more primitive knowledge of the pterosaur skull back in 1925. No known pterosaur has such a large quadratojugal, nor such an oddly shaped jugal.

References
Andres B, Clark JM and Xing X 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.
Padian K 2009. The Early Jurassic Pterosaur Dorygnathus banthenis (Theodori, 1830) and The Early Jurassic Pterosaur Campylognathoides Strand, 1928, Special Papers in Paleontology 80, Blackwell ISBN 9781405192248
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs, London (Salamander Books Ltd)192 pp.
Wiman C 1925. Über Dorygnathus und andere Flugsaurier. Bulletin of the Geological Institute of Uppsala, 19 (for 1923), 23–54.

wiki/Dorygnathus
wiki/Sericipterus

Another look at “Pterodactylus” spectabilis, actually a tiny dorygnathid

Today another tiny pterosaur
traditionally considered a juvenile (Wellnhofer 1970). And indeed, TM 10341 does look like a baby. But not a baby Pterodactylus, but a baby Dorygnathus (Figs. 1-3).

Figure 1. I didn't realize the teeth were so long in ?Pterodactylus spectabilis, TM10341,  n1 in the Wellnhofer 1970 catalog. This is no Pterodactylus, but a tiny dorygnathid. Click to learn more.

Figure 1. I didn’t realize the teeth were so long in ?Pterodactylus spectabilis, TM10341, n1 in the Wellnhofer 1970 catalog. This is no Pterodactylus, but a tiny dorygnathid from the Late Jurassic and the ancestor to the mighty azhdarchid, Quetzalcoatlus. Click to learn more.

?Pterodactylus spectabilis in situ, traced and reconstructed.

Figure 2. ?Pterodactylus spectabilis in situ, traced and reconstructed. The specimen is crushed and the premaxilla is twisted so that its right side is exposed, the opposite of the rest of the skull. Several of the anterior teeth make a jumble in the front.

TM 10341 (no. 1 in the Wellnhofer 1970 catalog) is a key taxon tying Dorygnathus to Beipiaopterus and the long metacarpal pre-azhdarchids like no. 44 and no. 42 in the large pterosaur tree. Note that TM 10341 does NOT have such a long metacarpal, so it’s lagging int this trait and is distinct from other short-tail pterosaurs. This lineage also gives rise to flightless pterosaurs, Huanhepterus, a ctenochasmatid- mimic and other tall, skinny pterosaurs like Quetzalcoatlus. They all had their origin in the cute, big-headed TM 10341 (Late Jurassic, Solnhofen).

TM 10341 had a reduced tail, a short antebrachium (radius + ulna) and a big head, but it was a tiny pterosaur. It looks like an adorable infant Dorygnathus, but we know from embryos that they actually have the proportions of adults, so TM 10341 is something new.  Since pterosaurs grew isometrically from hatchlings on up, so the changes that made TM 10341 “cute” all occurred in the egg or the gene.

This is one of the surviving remnants of Dorygnathus in the Late Jurassic. Others include the similarly reduced Scaphognathus and all of its ancestors from a different line of dorygnathids along with Ctenochasma and kin from a third lineage of dorygnathids.

Phylogenetic analysis nests TM 10341 after Dorygnathus and before Beipiaopterus (Fig. 3). No other tested taxa (202 at last count) are closer to TM 10341.

Figure 3. Three sister taxa to scale. At left, Dorygnathus SMNS 50164, middle Jurassic. Middle, ?Pterodactylus spectabilis, late Jurassic. Right, Beipiaopterus, Early Cretaceous. Size reduction was a driver in the evolution of new morphologies.

Figure 3. Three sister taxa to scale. At left, Dorygnathus SMNS 50164, middle Jurassic. Middle, Pterodactylus spectabilis, late Jurassic. Right, Beipiaopterus, Early Cretaceous. Size reduction and enlargement were drivers in the evolution of new morphologies.

Size reduction is what drives pterosaur evolution, bringing with it the largest changes in structure and proportion. Most of these changes are retained as subsequent taxa become larger and larger. Size reduction takes place when sexually mature half size adults lay half-size eggs over several to several thousand generations. TM 10341 was about 7.5 cm tall. Hatchlings of TM 10341 would have been only 1 cm tall.

References
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.