Behind the scenes: that infamous ‘pterosaur precursor’ paper

Earlier we looked at
a pterosaur precursor paper that excluded all the pterosaur precursors documented 20 years ago (Peters 2000, 2007, 2009). Those four taxa were dismissed and omitted by Ezcurra et al. 2020, who cobbled together a chimaera of protorosaur and lagerpetid parts. Notably the lagerpetid foot showed it stood on only two toes. Pterosaur tracks and skeletons show pterosaurs stood on five toes. And that’s just the beginning of the sins committed by this 18 co-author venture into the imagination of confirmation bias.

From Eurekalert.org:
“Some questions still remain in this evolutionary mystery. Now that lagerpetids are the closest relatives of pterosaurs, why are they still lacking some of the key characteristics of pterosaurs, including the most outstanding of those – wings?

“We are still missing lots of information about the earliest pterosaurs, and we still don’t know how their skeletons transformed into an animal that was capable of flight,” said Nesbitt.”

pterosaur wings

Figure 1. Click to enlarge. The origin of the pterosaur wing and whatever became of manual digit 5?

Actually we already know how pterosaurs got their wings.
We’ve known for ten or twenty years (depends if your measure by data or taxa). The authors cited twenty-year-old Peters 2000. The authors provided no evidence that they actually looked inside that paper. Perhaps they believed the current propaganda and just dismissed the hypothesis. There was also a bit of wish fulfillment going on. Many workers have been hoping for decades to find a taxon to link dinos with pteros (see below).

Reporter George Dvorsky, confesses on Gizmodo.com
“These creatures [lagerpetids] seem an unlikely sister group from which pterosaurs emerged, which is probably why they’ve been ignored for so long.”

Lagerpetids seem unlikely because they have no traits shared exclusively with pterosaurs and several that dislodge them from consideration. By contrast, the omitted Cosesaurus clade has a long list of traits shared exclusively with pterosaurs.

Professor Kevin Padian
wrote a News & Views article to accompany the paper and put Ezcurra et al.  into historical perspective. Padian also omitted the Peters 2000 paper, which really should have been part of the history of pterosaur origins. Instead Padian concentrated on 18th and 19th century papers (why not just reference the Bible?), plus 4 of 10 citations were for Padian papers from the past, none on pterosaur origins. One citation was for young J. Gauthier’s PhD thesis at the genesis of software enabled phylogenetic analysis in which the clade Ornithodira (= pterosaurs + dinosaurs) was proposed and widely accepted without testing the Cosesaurus clade. To his credit, Padian 1983 reported that Dimorphodon (Fig. 2) was a biped, like birds and dinosaurs and he has ‘stuck to his guns’ ever since.

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

Figure 2. Dimorphodon take off (with the new small tail).

I wrote to Dr. Padian:

Dear Kevin,

I’ll never forget the day when you and Chris Bennett gave me your sage words of wisdom: “Dave, you have to learn to perform a phylogenetic analysis.”

In 2000 when my Rivista paper came out on pterosaur origins, I added Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama to four previous published phylogenetic analyses. In each case those four nested closer to pterosaurs than all prior candidates… and for good reason. They shared more traits from snout to toes, including extradermal tissues.

Since then no one in the paleo community has let me know there are better candidates out there that I haven’t tested. On the other hand, no one has ever said, “Good job, you nailed it.”

Following your earlier advice I started adding taxa to a growing onliine cladogram at ReptileEvolution.com. Today there are 1770+ taxa on that one cladogram and the Cosesaurus clade still nests with pterosaurs, but they also nest within Lepidosauria in an overlooked third clade between sphenodonts and squamates.

It’s clear you have always preferred the ornithodire hypothesis, despite conflicting results when more taxa are added. Not sure why you stick to your guns when no evidence supports the hypothesis

Yesterday Ezcurra et al. came out with a chimaera they created out of a lagerpetid and a protorosaur that ran on two toes and called it a pterosaur precursor and you supported it with an enthusiastic news and views article, that, like Ezcurra et al. report, omitted the Cosesaurus clade.

You wrote, “Lagerpetids fit this profile, and, unlike other candidate relatives, they share some features with pterosaurs that other archosaurs do not.”

You also wrote,”Ezcurra et al. realized that, although lagerpetids didn’t fly, they share specific features with pterosaurs, such as … Their elongated hand (palm) bones (hyperelongated in pterosaurs, along with the fourth finger) suggest a good starting point for animals to evolve flight.”

By contrast, Ezcurra et al. wrote, ” …lagerpetids, as with other archosauromorphs, _lack_ the enlargement of both the deltopectoral crest of the humerus and the fourth manual digit that characterizes pterosaur wings.

We all see what we want to see. But my friends from Morristown NJ usually have a keener eye.

I was critical of Ezcurra et al. online here, with extensive evidence, if interested:

https://pterosaurheresies.wordpress.com/2020/12/10/new-pterosaur-precursor-study-excludes-all-pterosaur-precursors/

Best regards,

I have not heard back yet, and ironically, Dr. Padian is not famous for phylogenetic analysis.

Likewise I sent an email to co-author Max Langer:

Hi Max,

I was surprised, once again, to see Cosesaurus, Sharovipteryx and Longisquama omitted from a study on pterosaur origins. Very bizarre that taxa with prepubes, pterosaur-type pedes, extradermal membanes, antorbital fenestrae, four+ sacrals, elongate ilia, attenuated tails and a sternal complex were dismissed. 

Your new lagerpetid ran on two toes. That was the story, not any sort of relationship to pterosaurs.

Best regards,

I have not heard back yet.

Likewise I sent an email to lead author Martin Ezcurra
after he sent a PDF of the paper:

Thank you, Martin.

That is very kind of you to send the PDF. Fortunately someone else sent a copy in the meantime and I have been pouring over it.

I am going to be very critical of your paper. Here are the first two paragraphs.

It is good to see more material data appearing for lagerpetids, an enigmatic clade formerly known from pelvic and hind limb material and more recently from skull bits.

“Unfortunately Ezcurra et al. follow an established history of workers omitting competing taxa in pterosaur origin papers while cherry-picking comparative taxa and employing a chimaera of disassociated and unrelated bits and pieces from different genera. By contrast, the omitted taxa are complete, articulated, preserve soft tissue and nest closer to pterosaurs in several prior cladograms when added to them. Details follow.”

In addition, I think you missed some exciting details in the pes, overlooking fused bones. Your metatarsal 1 is actually metatarsal 2. Digit 1 is a vestige on this weird pes. Basal pterosaurs have five robust toes. Chanaresuchds lose pedal digit 5, so cannot be ancestral on that point alone. The taxa from Peters 2000 all have a robust pedal digit 5 on a short metatarsal, as in pterosaurs and as in Tanystropheus, which is why the first specimens of Tanystropheus were considered pterosaurian. Both are lepidosaurs, by the way.

Phylogenetically all the material continues to look chanaresuchid, not pterosaurian, as in prior lagerpetids.

Not sure who guided you not to include taxa from Peters 2000, 2007, 2009. Oh, well, it’s in print now. Most of the worst hypotheses on pterosaurs seem to come out of Southern England. Try to be more careful before accepting their suggestions.

This affair may remind you of the Oculudentavis scandal after a few days or weeks. Hopefully you’ll come out okay on the other end.

Best regards,

I have not heard back from Martin, either,

I only wish Ezcurra team and Padian
had been more critical of their own work (e.g. the two toes issue), had indicated they looked at the taxa in Peters 2000 and then rejected them and provided the reasons for that rejection, and contrary to that, simply shown their reconstruction of Cosesaurus, their reconstruction of Bergamodactylus and their reconstruction of their chimaera in one figure so readers could see their work for themselves with help from figure captions and call-outs. Figure 3 is from ReptileEvolution.com.

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Figure 3. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Please remember,
I was the second person to see pterosaur traits in Cosesaurus. Dr. P. Ellenberger was the first, but unfortunately, he thought Cosesaurus was a bird ancestor. He never considered pterosaurs. His views and tracings were chronicled here, here and here.

Together with the Oculudentavis scandal in March 2020,
this pterosaur precursor scandal and others, paleontology is going through a nadir right now. I hope things don’t get worse before they get better.


References
Ezcurra MD et al. (17 co-authors) 2020. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum.  Postilla. 189: 1–44.
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 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330

Cosesaurus paper on ResearchGate.net

https://gizmodo.com/scientists-uncover-the-mysterious-origin-of-pterosaurs-1845841696

https://pterosaurheresies.wordpress.com/2020/12/10/new-pterosaur-precursor-study-excludes-all-pterosaur-precursors/

2 thoughts on “Behind the scenes: that infamous ‘pterosaur precursor’ paper

  1. The two toes has even been illustrated if I remember correctly! More than that, even I as an interested layman know Lagerpetonids simply don’t fit in any way with pterosaur ancestry. It requires so many reversals and derived characteristics, it is rediculous!

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