Palaeontology [online]

Header for website paleontology online.

Header for website paleontology online. Click to go to the website.

A website (new to me, but looks like it’s been around for awhile) palaeontologyonline.com is, in their own words,

“Palaeontology [online] is a website covering all aspects of palaeontology. The site is updated with articles about the cutting edge of research, by the researchers themselves. These are usually written by experts in the field, but are aimed at non-specialists. Articles vary widely in their content: some serve as an introduction to palaeontological or interdisciplinary fields, while others outline events in the history of palaeontology. Some contributions include summaries of recent findings and advances in rapidly evolving disciplines, and some focus on a particular geographic region or time period. Finally, some of our articles are based on the experience of being a palaeontologist – what life and work is really like as a fossil worker.  Our online format allows researchers to explain their work with the aid of an unlimited number of figures and videos.”

Commissioning editors (who are responsible for inviting contributions and overseeing the website) are:

Russell Garwood: Invertebrate palaeontologist; Peter Falkingham: Postdoctoral research fellow in the fields of vertebrate palaeontology and ichnology (trace fossils); Alan Spencer: Palaeobotanist; Imran Rahman: Postdoctoral researcher in invertebrate palaeontology and evolutionary genetics.

Some great pages here. Check out this placodont page.

The pterosaur page was written by Dr. David Hone, who states, “The origins and the relationships of the pterosaurs have long been contentious, although a consensus is forming on both issues. Often confused with dinosaurs, pterosaurs are members of their own clade, but are close relatives of their more famous cousins.

Over the years, palaeontologists have hypothesized that pterosaurs originated from various parts of the reptile evolutionary tree. Very early researchers considered them to be the ancestors of birds or even bats, and for a long time it seemed that they were probably basal archosaurs (the clade that contains dinosaurs, birds, crocodilians and some other groups). More recently evidence has begun to stack up that they are a separate group to the dinosauromorphs (dinosaurs and their closest relatives) but that the two groups evolved from a common ancestor. Most researchers now support this position. This makes pterosaurs reasonably close relatives to birds, but they are not bird ancestors as is sometimes wrongly reported.”

Well, par for the course…
Sad to see when there actually is a verifiable better relationship out there, but then that would involve actually acknowledging the literature (Peters 2000, 2002, 2007, 2009, 2011) and/or testing candidates one vs. another. But nobody wants to do this without fudging the data or reducing the inclusion set. It’s time to either recognize the literature or argue with it. The large reptile tree found a long line of pterosaur ancestors between Ichthyostega and Longisquama. Almost any one will do, as we learned earlier with turtles and pterosaurs.

References
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2000b. 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. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
http://www.reptileevolution.com/pterosaur-wings.htm

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Something new in Eudimorphodon revealed by DGS

Some people are still having trouble with DGS as a technique. They think of it as something that is virtually guaranteed to spook a reconstruction. Instead of increasing confidence that parts have been correctly identified, they have no confidence in work that has the taint of DGS.

Here’s a step-by-step run through DGS on a familiar specimen, Eudimorphodon ranzii. Using DGS enabled the recognition of some oddly long posterior ribs (that were always visible, just ignored) and a wider than deep torso in a pterosaur for which these traits were not otherwise recorded.

Eudimorphdon ranzii (Zambelli 1973, Wild 1978) s a Late Triassic pterosaur known from an articulated crushed skeleton missing feet, tail and most of each wing (Figs. 1-3). Some parts are easy to see and trace, like the skull and sternal complex. Some parts are more difficult like the two pubes (Wild 1978 only found one by combining the two into an oddly broad prepubis),  the pelvis, and the odd arrangement of the posterior ribs.

Eudimorphdon ranzii with post cranial bones colorized.

Figure 1. Eudimorphdon ranzii with post cranial bones colorized.

Step one: Colorize the bones (Fig. 1)
Darren Naish seems to think this is okay if you know which bone is which ahead of time when looking at the specimen and you’re just making a visual presentation. I like to take it one step further and use DGS to segregate bones that are more difficult to identify. Here the pelvis is found. The dorsal ribs will precisely transferred to the reconstruction, not generically applied. As we’ve learned earlier, sometimes pterosaurs have the cross section of a horned lizard.

Figure 2. The colorized bones on a fresh canvas.

Figure 2. The colorized bones on a fresh canvas. Most tetrapods have shorter posterior dorsal ribs, but not here in Eudimorphodon. Lighter tones on the pelvis represent overlying bones, in this case vertebrae. It is important to put a numeral on each vert and rib because it is otherwise easy to become confused.

Step two: Transfer the colorized bones onto a fresh white background (Fig. 2)
Here we’re just trying to put the bones on a fresh canvas. You’ll note some bones are estimates based on vague clues as they appear beneath the sternal complex.

Figure 3. Moving colorized bones into a rough reconstruction.

Figure 3. Moving colorized bones into a rough reconstruction or Eudimorphodon. Here both pelves are shown as they appeared in situ. In figure 1 I jumped the gun and put the parts together.

Step three: Move the colorized bones into a rough assembly (Fig. 3)
Here we’re just trying estimate a body shape to make tracing the colored bones easier.

Figure 4. Lateral, dorsal and cross-sectional views of Eudimorphodon ranzii. Note the overlap of the posterior ribs over the hind limbs and the very wide torso.

Figure 4. Lateral, dorsal and cross-sectional views of Eudimorphodon ranzii. Note the overlap of the posterior ribs over the hind limbs and the very wide torso. The cross section shows the 2nd dorsal ribs and the 23rd. Note the small ischium which could only produce small eggs. A little taller and wider than we thought before. The forelimbs are pretty short relative to the torso.

Step four: Tracing the colorized bones for the final reconstruction. (Fig. 4)
If I just attempted a lateral view I would have missed out on the very broad posterior torso based on the length of the posterior ribs. So I create both a dorsal view and a cross section view. Note that the sternal ribs, rarely found on most pterosaurs, extend laterally to meet the dorsal rib tips in Eudimorphodon. This give it a slightly wider body anteriorly, increasingly wider posteriorly. This is an odd autapomorphy, but it is based on many ribs, so it can’t be ignored. As you can see from the in situ image (Fig. 1) those long posterior ribs were there all the time. They were simply ignored by myself and others.

Eudimorphodon: a little odder than we thought
That torso is odd. Rather than tapering toward the pelvis, as in many other pterosaurs and tetrapods in general, the posterior torso is flat and wide, roofing the femora. My guess it provides a greater volume for eggs or respiration. With such small eggs, more eggs could have been carried by the mother. Note that the predecessor of E. ranzii, MPUM 6009, has a much deeper pelvic opening, likely to produce one large egg at a time. Note the reduction of the pelvis is also reflected in the reduction of the number of sacrals to four or five depending on the connection to the posterior pelvis.

Now
If there is anything wrong with the results here, please let me know. If not feel free to use the technique yourself. I think it works pretty well.

I also don’t make these identifications without entering the taxa into a phylogenetic analysis that typically finds the same traits in sister taxa. Unfortunately posterior ribs are virtually unknown among Triassic and Early Jurassic sisters.

Pterosaur workers haven’t produced too many Eudimorphodon reconstructions, and certainly none that have recovered the oddly long posterior ribs. My earlier reconstructions were given generic ribs. So I did a bad thing. I went along with the paradigm of a tubular pterosaur body without testing that paradigm. While it takes a lot of work for small discoveries such as this, and the results are minor changes, well, I had nothing better to do on a quiet Sunday.

References
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.
Zambelli R 1973. Eudimorphodon ranzii gen.nov., sp.nov. Uno Pterosauro Triassico. Rendiconti Instituto Lombardo Accademia, (rend. sc.) 107: 27-32.
wiki/Eudimorphodon

Pterosaur origins according to Wikipedia

Not sure
who has established him/herself as the editor of the “Pterosaur” article in Wikipedia, but there was a falsehood in there that had to be edited.

With regard to the “Origins” section, as I read it, the author reported that I did not view the fossils themselves. However, the author approved the Hone and Benton 2007 supertree analysis and the 2011 Nesbitt 2011 archosaur family tree.

The opposite is actually true. 
I had first hand access to Longisquama, Sharovipteryx, Cosesaurus, Langobardisaurus and Macrocnemus, taxa that are related to pterosaurs in order of  increasing phylogenetic distance (Longisquama is the closest). Hone and Benton, as in all authors of supertree analyses, did not even look at these specimens, but reported they were going to join together previous pertinent trees. Instead they only combined the trees they liked. They deleted Peters (2000) from their analysis and added a few typos to the scores to justify their deletion, as we discussed earlier. So there was no Bennett vs. Peters “contest.” W.C. Fields echoed their feelings when he said, “Go away, boy… you bother me.”

So, kids, this is what we’re dealing with.
No one wants to look at fenestrasaurs and there are people out there who are willing to flip the truth.

Not sure
how long the edit will stand. Wikipedia can edited by anyone. Just thought you should know…

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 Triassic Pterosaur Gastric Pellet – Reconstructed

This is the first in a series of Triassic pterosaur enigmas.

Figure 1 From Dalla Vecchia et al. 1983. Original identification of the pterosaur pellet elements. Scale bar = 1 cm.

Figure 1 From Dalla Vecchia et al. 1983. Original identification of the pterosaur pellet elements. Scale bar = 1 cm. Slightly distorted to match the published photograph. cV= caudal vertebra. Cv = cervical vertebra.

An odd jumble of Triassic bones was identified by Dalla Vecchia, Muscio and Wild (1983) as the remains of Preondactylus (Fig. 2), one of the few Triassic pterosaurs known at that time, in a gastric pellet (aka: vomited bones). The problem is, if you put the bones, as originally identified, on a reconstruction of Preondactylus, you’ll find a few matches and several mismatches (Fig. 1).

Figure 1. The major bones of the Triassic gastric pellet placed upon the skeleton of Preondactylus, a contemporary pterosaur. Note the several mismatches.

Figure 2. The major bones of the Triassic gastric pellet placed upon the skeleton of Preondactylus, a contemporary pterosaur. Note the several mismatches.

Generally the wing finger elements are too gracile and so is the femur. The dorsals are a bit too long and metacarpal 4, the base of the wing, is not quite large enough.

Putting the originally traced bones together in a different, yet still Triassic way, yields a pre- or proto-pterosaur with some resemblance to Longisquama. Now the more gracile and possibly much shorter wings make some sort of sense, because this was not a flyer, but a running flapper and a glider at best. Of course, in this case, I was able to draw the imagined parts “to fit.”

Freddy Mercury put it best, “Is this the real life? Is this just fantasy?”

Figure 2. With so few bones, and so few of those complete, you can rebuild the gastric pellet into a pre- or proto- pterosaur, something like Longisquama.

Figure 3. With so few bones, and so few of those complete, you can rebuild the gastric pellet bone tracings of Dalla Vecchia et al. into a pre- or proto- pterosaur, something like Longisquama. Now the femur becomes a distal humerus. What was a metatarsal becomes a metacarpal similar in size and thickness to metacarpal 4. The large dorsals are a good fit as Longisquama had a long torso. Minimizing the amount of bone lost from each of the wing/finger phalanges yields a much shorter wing, like Longisquama. Black wiry shapes are completely imagined, as is most of the rest of this restoration. The actual animal shape may never be adequately known.

Wouldn’t it be exciting if the gastric pellet, now known for over 30 years, turned out to be an example of a transitional/basal taxon? Odd that only segments of all four wing phalanges would be preserved.

After producing these images I learned the pellet is under study once again. Hopefully those studies will help resolve this mystery.

When I ran the published images through DGS I was able to identify many other bones and create another much more complete reconstruction that also made sense. It was standard basal pterosaur. But then, the data I was using was poor at best.

Given the mishmash of the in situ fossil, the poor quality of my data and the detailed new study of the gastric pellet specimen to come, I hesitate putting it out early. I will say that the originally identified ‘palatine’ and ‘pterygoid’ are probably the first two dorsal ribs, which were more robust than the others, as in other pterosaurs. And several more ribs are present, which were generally overlooked in the original tracing (Fig. 1).

References
Dalla Vecchia FM, Muscio G and Wild R 1983. Pterosaur remains in a gastric pellet from the Upper Triassic (Norian) of Rio Seazza Valley (Udine, Italy). Gortania – Atti Museo Friul. Storia Naturale 10(88):121-132.

Benton 1985 on pterosaurs

Benton 1985 was an early cladistic analysis done without a published matrix. Benton nested pterosaurs between Rhynchosaurs and Younginiforms + Lepidosaurs (that’s a stretch!). He did not report which pterosaur(s) he used in analysis.

Benton wrote: “Pterosaurs have typically been regarded as archosaurs that had their ancestry among the thecodontians (e.g. Romer, 1966; Wellnhofer, 1978). However, Wild (1978) has described two late Triassic genera on the basis of good material (Eudimorphodon, Peteinosaurus) , and he has made the proposal that the pterosaurs arose directly from ‘eosuchians’ and are not true archosaurs. Pterosaurs possess an antorbital fenestra, but Wild (1978: 247) considered that this may be a convergence. Further, Wild ( 1978: 246-253) reviewed numerous similarities between the early pterosaurs and various ‘eosuchians’ and differences from early thecodontians. The characters shared with Youngina, Prolacerta and others are all primitive to diapsids as a whole, except for the reduced quadratojugal, the ossified sternum, the ‘hooked’ 5th metatarsal, and the 3-pointed teeth seen in Eudimorphodon.

Until Peters 2000, Wild (1978) was the sole voice doubting the affinity of pterosaurs with archosaurs. Neither Wild nor Benton realized that the diapsid configuration arose twice in reptile phylogeny, as shown by the large reptile tree because their test did not include primitive reptiles.

Benton wrote: “Pterosaurs display all of the characters of the Neodiapsida as far as can be determined, except B2 (ventral processes on parietals) and B6 (emarginated quadrate). They show some archosauromorph synapomorphies (C4-10), but lack others: C1-3, 11-14. Pterosaurs share two characters with the Lepidosauromorpha: the single ossified sternum, and specialized sternal attachments for the ribs. The most parsimonious position for the pterosaurs at present is within the Archosauromorpha, as sister-group to all other archosauromorphs. Further work is needed on this question as well as on the suggestion that Pterosauria are the sister-group of Aves (Gardiner, 1982).”

Benton, to his credit, at least gave a nod to the lepidosauromorph traits. He noted pterosaurs shared 6 archosauromorph traits, but lacked 7 others.

According to Benton, archosauromorph traits shared with pterosaurs:

C4. Loss of tabulars. Benton notes they are also lost in lepidosaurs.

C5. Stapes without a foramen. I don’t think stapes have ever been identified in pterosaurs, but living lepidosaurs retain a heavier stapes with a foramen, according to Benton. Huehuecuetzpalli, at the base of the Tritosauria, does not show a foramen, but then it is only partly exposed.

C6. Vertebrae not notochordal. Benton notes that Sphenodon and geckos retain notochordal verts. Reynoso (1998) reports that Huehuecuetzpalli had amphicoelous verts, a trait shared with pterosaurs.

C7. Transverse processs on dorsal vertebrae project as distinct narrow elongate processes. Benton’s samples are all large reptiles. We don’t see these on pterosaur ancestors until Macrocnemus and all of its descendants among the tritosaurs.

C8. Cleithrum absent. Also absent on Huehuecuetzpalli. 

C9. No entepicondylar foramen in the humerus. Benton notes that lizards lose this too. Huehuecuetzpalli retains one. Cosesaurus does not have one.

C10. Loss of foramen in carpus between ulnare and intermedium. Benton notes this is lost in Squamata.

So that’s his list. Not much to say the least. I was hoping for more.

According to Benton, archosauromorph traits lacked in pterosaurs include:

C1. Premaxilla extends behind naris. Benton is wrong here, but Huehuecuetzpalli shares this trait.

C2. Nares elongate and close to midline. Benton is wrong here. Huehuecuetzpalli shares this trait.

C3. Quadratojugal (if present) located mainly behind the lower temporal fenestra. Benton is wrong here, but the same morphology is present in Cosesaurus.

C11. Presence of a lateral tuber on the calcaneum. Benton is correct! But no lateral tuber is found on Huehuecuetzpalli. 

C12. Complex concave-convex articulation between the astragalus and calcaneum. Correct, but the same is found on Huehuecuetzpalli.

C13. Fifth distal tarsal lost. Correct, but the same is found in Huehuecuetzpalli.

C14. Fifth metatarsal hooked without lepidosaur specializations. These include: ‘hooked’ in two planes. According to Benton mt5 bears specialized plantar tubercles, and it passes into the tarsus over the proximal end of the 4th metatarsal. Benton may be right. In any case pterosaurs and Huehuecuetzpalli have the same kind of mt5. In Pteranodon the metatarsus is reduced to being hooked in one plane.

Benton did not realize the rampant homoplasy in the reptilia.
The HI (Homoplasy Index) of the large reptile tree is over 0.90. So, exceptions and convergences abound within the reptilia. Very few traits are found in one and only one clade.

Benton mentioned Cosesaurus briefly, noting in the original description a long antorbital fossa (but he quoted the original French). He lumped it with Malerisaurus in “Prolacertiformes, incertae serdis”, not realizing that Cosesaurus was a tritosaur, along with Macrocnemus, Tanystropheus and Tanytrachelos, which he also considered prolacertiformes. Longisquama and Sharovipteryx, the two taxa closest to pterosaurs, were not considered.

The Gardiner (1982) paper mentioned by Benton has been largely ignored, and for good reason. Not sure why it was even included, but then, we’re talking about 1985 here. We’ll look at Gardiner 1982 tomorrow.

Bottom line:
With wrong, tenuous and convergent evidence Benton 1985 found pterosaurs nested outside the archosauromorpha. Later workers, who merely looked at the conclusions without questioning the evidence, accepted Benton’s conclusion. And look where that has brought us.

Later Hone and Benton (2007, 2009) applied the same lax interest and disposal of data to show that pterosaurs probably nested close to archosauromorphs after deleting the only competing candidate taxa. We looked at those problems in detail here.

I think it all comes down to conservatism. The same sort of conservatism that dismissed Wagner’s (and others) hypothesis on continental drift, Heyerdahl’s hypothesis on western migration to Polynesia and the static, earth-centered universe. Those days are not yet over.

References
Benton MJ 1985. Classification and phylogeny of the diapsid reptiles. Zoological Journal of the Linnean Society 84: 97-164.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Reynoso V-H 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodríguez, Central México. Philosophical Transactions of the Royal Society, London B 353:477-500.

New Pterosaur Tree – Andres and Myers 2013

Pterosaur worker, Brian Andres, has produced a larger pterosaur tree than prior efforts by combining those prior efforts (Fig. 1). This was part of his 2010 PhD dissertation. The Wiki version (easier to read) can be seen here. I understand this tree will appear in a forthcoming (2014) volume entitled, “The Pterosauria.” Hope it avoids all past pitfalls, but judging by this tree (Fig. 1) and the description of the volume (“important new finds such as Darwinopterus“) we are due for another few years in the “dark ages.”

Sorry about that, kids. l’m really trying to fix things here by pointing out obvious errors.

According to Wikipedia
Andres’ phylogenetic analysis combines data mainly from three different matrixes: Kellner’s original analysis (2003) and its updates (Kellner (2004), Wang et al. (2005) and Wang et al. (2009)), Unwin’s original analysis (2003) and its updates (Unwin (2002), Unwin (2004), Lu et al. (2008) and Lu et al. (2009)) and previous analyses by Andres et al. (2005), Andres and Ji (2008) and Andres et al. (2010). Additional characters are taken from DallaVecchia (2009), Bennett’ analyses (1993-1994) and various older, non-phylogenetic, papers.

Figure 1. Click to enlarge. Pterosaur family tree produced by Andres 2010 and in press. Color added to show clades according to the large pterosaur tree that included several specimens of certain genera and included tiny pterosaurs, lacking here.

Figure 1. Click to enlarge. Pterosaur family tree produced by Andres 2010 and in press. Color added to show clades according to the large pterosaur tree (that included several specimens of certain genera and included tiny pterosaurs, lacking here). The indigo bar by Eosipterus indicates one specimen is indeed a ctenochasmatid, but the other is a germanodactylid, as we covered earlier. So, specimens are needed here, not just genera.

It’s big but still incomplete
Andres’ taxon list excludes distinct variations within certain genera, like Dorygnathus and Scaphognathus, that proved important in the large pterosaur tree. Andres’ taxon list also excludes all tiny pterosaurs. Those likewise proved important in the large pterosaur tree.

Strange bedfellows
The Andres’ tree nested several taxa that also nest together in the large pterosaur tree. However, the Andres tree also produces several nesting partners that don’t look alike. They don’t share many traits. For instance, Andres tree nests the basal anurognathid Dendrorhynchoides with the germanodactylids (Fig. 2) at the base of the “pterodactyloidea.” Few pterosaurs are so different from one another. It seems improbable that one would evolve from the other. In the large pterosaur tree this transition actually was several convergent transitions — and all sister taxa document a gradual accumulation of derived traits — not the skull-jarring leap shown here (Fig. 2).

Figure 3. According to Andres these two pterosaurs are sisters. This, obviously, is erroneous.

Figure 2. According to Andres these two pterosaurs are sisters. This, obviously, is erroneous.

Andres tree also nests the dorygnathid, Parapsicephalus (= Dorygnathus) purdoni with Dimorphodon (Fig. 3). Again, these two share very few traits. Click on the links above to see and read about pterosaurs that are more similar to these two, and you’ll see what I mean.

Figure 4. According to Andres, these two pterosaurs are close sister taxa. According to the large pterosaur tree, they nest far apart.

Figure 3. According to Andres, these two pterosaurs, Dorygnathus and Dimorphoson, are close sister taxa. According to the large pterosaur tree, they nest far apart.

There are several other misfits in the Andres tree, as shown by the various color codes (Fig. 1) that represent clades in the large pterosaur tree. For instance, Andres tree doesn’t recognize that azhdarchids and chaoyangopterids evolved from protoazhdarchids, like Beipiaopterus and Huanhepterus.

Some highlights
Andres tree does not put darwinopterids at the base of the “pterodactyloidea” but between Sordes and Changchengopterus and close to Scaphognathus. This is very close to results of the large pterosaur tree (Fig. 4).

Figure 1. Click to enlarge. Unwin and Lü note a resemblance between Darwinopterus and Germanodactylus. And that is certainly so, but only by convergence. Phylogenetic analysis indicates a closer relationship between the descendants of Scaphognathus and Germanodactylus. Arrows indicate phylogenetic order. Here the long neck evolved first with a smaller skull. Then the skull became longer in the lineage of Darwinopterus.

Figure 4. The evolutionary lines that gave rise to Germanodactylus and Darwinopterus according to the large online pterosaur tree by yours truly. Small changes, gradual accumulations of derived traits are shown here. No strange bedfellows.

Andres nests the Triassic Raeticodactylus and Preondactylus at the base of the Pterosauria. While MPUM6009 is ancestral to both, these nestings are not bad (Fig. 5).

The origin of the Pterosauria from basal Fenestrasauria

Figure 5. The origin of the Pterosauria from basal Fenestrasauria. This image is not current, but will update when enlarged. Note: Euparkeria is not involved here.

Some lowlights
Andres tree nests most ornithocheirids following the pteranodontids (Fig. 6). This means large teeth reappeared on a broad rostrum evolving from a toothless sword-like rostrum. Sharp rostrum germanodactylids make better ancestors for pteranodontids and scaphognathids make better ancestors for ornithocheirids via Yixianopterus (Fig. 6). The warp in the humerus deltopectoral crest is distinct in ornithocheirids and pteranodontids and evolved convergently.

Figure 6. Left - evolutionary lineage according to Andres in which toothless pteranodontids give rise to toothy ornithocheirids. On the right, corrected lineages for each.

Figure 6. Click to enlarge. Left – evolutionary lineage according to Andres in which toothless pteranodontids give rise to toothy ornithocheirids. Right –  corrected lineages for each clade.

At the base of the pterosaurs Andres uses the derived erythrosuchid, Euparkeria, which shares no traits with pterosaurs. He would have been better off using a tritosaur or fenestrasaur, but chose to ignore the literature on pterosaur origins (Peters 2000, 2002, 2007).

Andres nests anurognathids with darwinopterids in a false clade, “monofenestrata” in which the naris and antorbital fenestra are supposed to be confluent, evidently based on the bogus reconstruction of Anurognathus by Bennett 2007, which we dismantled earlier here and here.

Some thoughts
Since so many pterosaurs are preserved in a crushed fashion it is imperative that they be reconstructed in order to ascertain the identification of bony elements. Few other workers attempt this and Andres is not known for doing so.

It is also imperative that pterosaur workers know what a pterosaur is. Phylogenetic analysis (Peters 2000, 2007 and online studies) and character analysis (Peters 2013) demonstrate pterosaurs are not related to archosaurs, like Euparkeria, but to tritosaur fenestrasaurs.

Finally it is imperative that pterosaur workers employ the tiny pterosaurs in their analyses. The family tree will never make sense and will never produce gradual accumulations of derived characters unless the tiny pterosaurs are included.

References
Andres BB 2010. Systematics of the Pterosauria PhD dissertation. Yale University, 2010, 366 pages; 3440534
Andres B and Myers TS 2013. Lone Star Pterosaurs. Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 103: Issue 3-4, p 383-398.
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
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. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2013. A gradual accumulation of pterosaurian traits within a series of Lepidosauriformes. Rio Ptero Symposium 2013.

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