Cosesaurus vs. Saller 2016

Nobody wants Cosesaurus aviceps to be a pterosaur ancestor.
Everyone in paleo prefers pterosaurs to be closely related to dinosaurs and their last common ancestor, which is, according to Nesbitt 2011, a phytosaur. This is continually ‘proved’ in pterosaur studies by excluding Cosesaurus (e.g. Hone and Benton 2007, 2009; Benton 1999; Nesbitt 2011) and in Cosesaurus studies by omitting pterosaurs (e.g Saller dissertation 2016). Saller 2016 claims to not see pterosaur traits in Cosesaurus (Fig. x). That is because Saller did not include pterosaurs in his analysis.

Whoever is writing the Wikipedia page on Cosesaurus accepts Saller’s freehand interpretation (Fig. 1) and prefers Saller’s refusal to add pterosaurs to his cladogram. We talked about putting metaphorical ‘blinders’ on earlier.

Figure 1. Cosesaurus insitu. No bones are present. This is a natural mold that includes an amorphous blob, a jellyfish, that trapped one foot of this unique specimen.

Figure x. Cosesaurus insitu. No bones are present. This is a natural mold that includes an amorphous blob, a jellyfish, that trapped one foot of this unique specimen. This is about natural size.

Today we’ll take another look
at the tiny mold fossil that is Cosesaurus. It preserves a nearly completely articulated tiny lepidosaur tritosaur tanystropheid fenestrasaur (according to the large reptile tree, LRT, 1401 taxa) so sensitively preserved that it shares the matrix with an amorphous medusa (jellyfish) clearly presented.

Saller (p.148) wrote (Google translated from the original Italian):
“At the base of the orbit there is a depression that has been interpreted as a window  antorbital from Ellenberger (1977) and from Peters, which even distinguishes three antidotal windows (Peters, 2000). While the presence of a depression is certain, the conditions of conservation and the difficulty in identifying the sutures among the various elements makes it difficult to propose one of his own reliable interpretation. If it were really an antorbital window, this circumstance, together with the poor development of the subnarial process of the premaxillary, they would be elements a support of the hypothesis of an affinity with the pterosaurs.” 

Is an antorbital fenestra present in Cosesaurus?
Saller said he saw only a depression. You decide by examining these several pictures of the skull of Cosesaurus in various lighting angles (Fig. 1).

Figure 1. The skull of Cosesaurus traced using DGS methods and lit at various angles. Some of these are negatives of a negative mold, giving a positive view. Saller was not sure about the antorbital fenestra, probably because it is represented by an elevated portion in the mold.

Figure 1. The skull of Cosesaurus traced using DGS methods and lit at various angles. Some of these are negatives of a negative mold, giving a positive view.  See how they change, revealing new details? Black dot is a fossil air bubble. Judge for yourself whether or not you see an antorbital fenestra here. Compare this skull with Bergamodactylus, the basalmost Triassic pterosaur.

We must let Saller 2016 finish his thought (from above):
The analysis of the postcranial skeleton [of Cosesaurus] offers however, very little space for this interpretation.” So, Saller denies or discounts what he sees on the rostrum, because he does not see pterosaur traits in the post-crania. [ Hello, Larry Martin! ] Even so, by not including any pterosaurs in his cladogram, Saller fails to test the possibility that just an antorbital fenestra is enough to make Cosesaurus a transitional taxon basal to pterosaurs.

Don’t drop the ball when you’re just about to make a touchdown.
Was PhD candidate Saller advised to not test pterosaurs in his cladogram? I’d like to find out. 

If the post-crania is Saller’s only anti-pterosaur issue, 
let’s take another look at the various post-cranial pterosaur traits found in
Cosesaurus that Saller did and didnot see. It will help to segregate them using DGS methodology.

Figure 2. Cosesaurus torso and forelimbs. The hot pink stem-like coracoids are found in pterosaurs. So are the strap-like scapula, distinct from the discs found in Macrocnemus. There is a close association of the clavicles, interclavicle and sternum. In pterosaurs this is known as a sternal complex.

Figure 2. Cosesaurus torso and forelimbs. The hot pink stem-like coracoids are found in pterosaurs. So are the strap-like scapula, distinct from the discs found in Macrocnemus. There is a close association of the clavicles, interclavicle and sternum. In pterosaurs this is known as a sternal complex. Note how the humerus disappears when the lighting angle changes. That little sphere is a fossilized air bubble. Yellow frills are feathery, pro-aktintofibrils. 

Some data are hard to ‘see’ even under a microscope.
Some data need to be visually segregated in order to see what is really going on in a fossil. Saller gives no indication that he traced any portion of Cosesaurus for his dissertation. Nor did he create a negative of the negative mold. I can tell you from leaning over a microscope looking at Cosesaurus in Barcelona, it is impossible to comprehend this specimen without creating a positive and using tracings to help simplify and segregate elements on a computer monitor. Saller did not use all the tools at his disposal. Neither did I while writing Peters 2000. Now I know better.

Here (Fig. 2) DGS methods segregate the pectoral elements from the ribs and gastralia. The coracoids have a curved stem, as in the Triassic pterosaur, Bergamodactylus— distinct from the discs in more basal tritosaurs/tanystropheids. The sternum, interclavicle and clavicles are coincident and just about to fuse in Cosesaurus, creating a sternal complex, as in pterosaurs—distinct from more basal tritosaurs/tanystropheids. Saller 2016 did not see this.

Saller reports he did see the strap-like scapulae, distinct from the discs found in Macrocnemus… and even though the pterosaur traits keep adding up by Saller’s own admission, still that was not enough to add pterosaurs to his cladogram. Is this an example of peer-group pressure?

Why does the humerus disappear
when the lighting angle is moved (Fig. 2)? Because it is crushed upon the dorsal vertebrae. Only certain lighting angles reveal the right humerus. Why does it crush so completely? Because it is hollow. Can you name another small Triassic reptile with extremely hollow arm bones?

Figure 3. The pelvis of Cosesaurus with prepubis in green and 5 sacrals, not 2 as Saller interprets the fossil.

Figure 3. The pelvis of Cosesaurus with prepubis in green and 5 sacrals, not 2 as Saller interprets the fossil.

Saller 2016 looked at the pelvis
and reported only two sacrals present, despite the long ilium he noted. There are five sacrals in Cosesaurus. Sacral are added in response to a bipedal stance — needed whenever flapping its arms (remember the stem-like coracoid is the clue to this behavior).

Saller failed to see the prepubes. One is pretty obvious here (Fig. 3 in green), but I missed it, too prior to writing Peters 2000.  Prepubes add anchors for femoral adduction, which happens when the knees are brought closer to the midline, typically for bipedal locomotion.

More pterosaur traits tomorrow. 


Just in time—a pertinent quote from Dr. John Ostrom,
“With the announcement of the first dinosaurs with feathers from China, Ostrom (then age 73) was in no mood to celebrate. He is quoted as saying‘I’ve been saying the same damn thing since 1973, `I said, `Look at Archaeopteryx!’” 


References
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier 12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117.
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências (2015) 87(2): (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
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 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Saller F 2016. Anatomia, paleobiologia e filogenesi di Macrocnemus bassanii Nopcsa 1930 (Reptilia, Protorosauria). Alma Mater Studiorum – Università di Bologna Dottorato di Ricerca in Scienze della Terra Ciclo XXVII 206pp.
Sanz JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753.
Wild R 1993. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95-120.
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.

wiki/Bergamodactylus
wiki/Cosesaurus

11 thoughts on “Cosesaurus vs. Saller 2016

  1. “Was PhD candidate Saller advised to not test pterosaurs in his cladogram? I’d like to find out.”
    “…Is this an example of peer-group pressure?”

    With all that in mind, have you talked to Saller about any of this?

  2. For those who do not know, I have added Dimorphodon, Eudimorphodon, and Eoraptor into the dataset of Saller (2016) without any other alterations. My results consistently place pterosaurs sister to Eoraptor, with this clade having consecutive sister taxa of Euparkeria, Proterosuchus, and Prolacerta. At no point are pterosaurs considered close to Cosesaurus or other tanystropheids.

    • Saller and NP scored Cosesaurus as having few to none of the above pterosaur traits. So, what Saller and NP scored as Cosesaurus was actually an imaginary taxon.

      Moreover, Saller and NP did not include Gephyrostegus, Silvanerpeton as outgroup taxa to the basal dichotomy splitting the new Lepidosauromorpha and Archosauromorpha, nor did they include a long list of basal Lepidosauromorpha and Archosauromorpha that split protorosaurs from tritosaurs in the LRT. Without these outgroups these two convergent clades mix with one another, a traditional error based on taxon exclusion.

      Finally, NP sent me his rough and largely incomplete misidentification of several Cosesaurus bones based on his biased preconceptions.

      My advice to him was to see the specimen in person, as I did; trace every bone using a method that graphically segregates the several layers, as I did; create a reconstruction using the traced elements without resulting to a freehand cartoon, as he and Saller did, to make sure all the bones fit without bias, as I did; and then to add the data to a large gamut cladogram that includes several Carboniferous, Permian and Triassic ancestors, as I did.

      Unfortunately NP is reporting results in which much more work needs to be done, both in data collection and taxon inclusion. I encourage him to keep working! He has a long way to go given the results he reports. Eoraptor, as everyone knows, shares few to no traits with pterosaurs. No one else has reported this relationship. And where was Scleromochlus? Not included.

      Saller’s 2016 dissertation was intended to focus on the many European specimens attributed to Macrocnemus. Based on the literature Saller must have felt he was obliged to comment on Cosesaurus. It is clear from his description that Saller eyeballed the specimen with a microscope without producing a precise tracing, a method he used on the other European macrocnemids.

      I fully sympathize with those who say they cannot ‘see’ certain traits in Cosesaurus, like dorsal ribs below the gastralia. All prior workers, including Peters 2000, made mistakes with this specimen. It really takes DGS, several lighting angles, a long taxon list and more experience than I had 19 years ago to understand exactly what is happening in this specimen, all presented above.

      In private correspondence with NP I counseled him to consider the above paths to a better understanding of Cosesaurus. He has chosen not to do so with the above declaration.

      • My analysis is incomplete and I am not at leisure to examine the specimen in person. My identifications are based on impressions visible to me in pictures, and it is true that I did not use DGS because I find that method unusable in this circumstance given that the specimen is an impression (without any actual bone material) on grainy sediment. My interpretations are by no means a precise answer to questions on the osteology of Cosesaurus.

        It would take an unbiased and peer-reviewed scientific inquiry with repeatable and reliable methods to resolve that question. Such a study does not currently exist. Dave has said that if I want such a study to exist, it is my choice to create it. But I do not have the time, money, or expertise to do so, and my refusal to follow that path is not a matter of stubbornness or laziness. I am simply acknowledging that I am not on a position where I can fulfill all of his requests towards the paleontological community.

        Nevertheless, I still wanted to inform the readers that someone has incorporated pterosaurs, dinosaurs, and tanystropheids like Cosesaurus into Saller’s analysis. And that it found that a connection between tanystropheids and pterosaurs is significantly less likely compared to one between pterosaurs and dinosaurs, based on the data I entered. Eoraptor has been objectively demonstrated to share quite a few traits with pterosaurs, contrary to your (subjective) declaration. I find your suspicions that Saller and his advisor had ulterior motives not to incorporate pterosaurs to be unfounded and abrasive, and I just wanted to lay out my results so that your readers have a second opinion on the matter.

        P.S. Adding Gephyrostegus and Huehuecuetzpalli did not change these results. The LRT’s basal Lepidosauromorpha/Archosauromorpha split is a subject separate from pterosaur relationships. This is a question of whether it makes more sense for pterosaurs to be derived from tanystropheids or dinosaurs.

      • Neil Pezzoni wrote: “My interpretations are by no means a precise answer to questions on the osteology of Cosesaurus.”

        As I said, the NP (=Neil Pezzoni) analysis employed an imaginary taxon with invalid scoring. He came to this analysis with a biased mind set and his results reflect that bias.

        So, let’s go with that bias: Now would be a good time for Neil to tell us what traits unite pterosaurs with Eoraptor to the exclusion of all tested taxa including Cosesaurus. And why, after viewing the data presented above he still does not accept the evidence presented, preferring his own “identifications…based on impressions visible to me in pictures.”

        Neil Pezzoni wrote: “The LRT’s basal Lepidosauromorpha/Archosauromorpha split is a subject separate from pterosaur relationships.” That untested opinion was falsified about seven years ago by the LRT. It is germane to this discussion.

        Unfortunately Neil Pezzoni is experiencing cognitive dissonance, unable to accept a wide gamut of evidence in favor a previously embraced paradigm. This is a common experience in paleontology, which is why the Ostrom quote was presented as a postscript to the text.

  3. It is true that I experience bias (if you can call it that) towards the mainstream paleontological community and away from Ellenberger’s work. Dave experiences an opposite bias as he has confidence in the methodology of Ellenberger and little confidence in that of mainstream paleontological workers. If Dave is willing to present evidence found through reliable and reproducible methods (rather than DGS, which has not been demonstrated to be reproducible), I would be happy to accept it.

    As for traits that unite Eoraptor and pterosaurs to the exclusion of Cosesaurus and other tanystropheids, here are a few found by my analysis:

    *Small retroarticular process (likely convergent, as several other dinosaurs have a large retroarticular process)
    *Loss of the supratemporal bone (presence unclear in tanystropheids)
    *No astragalocalcaneal foramen
    *Lower temporal fenestra enclosed from below
    *Presence of a laterosphenoid (Dave’s identification in Cosesaurus just looks like the flattened frontal and parietal bones to me)
    *Curved, serrated, and laterally compressed teeth (only in Dimorphodon among pterosaurs)
    *Mandibular fenestra (only in Austriadraco among pterosaurs)
    *Postfrontal does not form the border of the upper temporal fenestra

    • Actually, Neil, I don’t trust the methodology of Ellenberger or any other worker. I test the methodology of carefully looking at specimens, scoring their traits and letting software determine relationships. This is a methodology that is universally used by mainstream paleontological workers. Is this reproducible? Yes. When it is done. Saller did not use this methodology.

      As for traits that unite Eoraptor and pterosaurs to the exclusion of Cosesaurus and other tanystropheids, you’ve been falsified.

      *Small retroarticular process (likely convergent, as several other dinosaurs have a large retroarticular process)
      Cosesaurus, Sharovipteryx and Longisquama share this trait, as do many tetrapods. This is not exclusive to this purported clade.

      *Loss of the supratemporal bone (presence unclear in tanystropheids)
      Cosesaurus, Sharovipteryx and Longisquama share this trait, as do many tetrapods. This trait is not exclusive to this purported clade.

      *No astragalocalcaneal foramen
      Cosesaurus, Sharovipteryx and Longisquama share this trait, as do many tetrapods. This trait is not exclusive to this purported clade.

      *Lower temporal fenestra enclosed from below
      Cosesaurus and Longisquama share this trait, as do many tetrapods. Sharovipteryx is exposed dorsally. This trait is not exclusive to this purported clade.

      *Presence of a laterosphenoid (Dave’s identification in Cosesaurus just looks like the flattened frontal and parietal bones to me)
      Cosesaurus shares this trait, as do many tetrapods. Typically the parietal is not visible through the orbit in tetrapods. This trait is not exclusive to this purported clade. Not exposed in Sharovipteryx and Longisquama.

      *Curved, serrated, and laterally compressed teeth (only in Dimorphodon among pterosaurs)
      _Only_in Dimorphodon, a derived pterosaur. Larry Martin would be pleased to see this. This trait is not exclusive to this purported clade.

      *Mandibular fenestra (only in Austriadraco among pterosaurs)
      This was debunked here: https://pterosaurheresies.wordpress.com/2011/11/18/did-dimorphodon-have-an-external-mandibular-fenestra/ Again, Larry Martin would be proud, but that surangular tends to shift during taphonomy. In that specimen the entire pterosaur has shifted (disappeared), leaving only a mandible exposed in medial view, lacking a surangular.

      *Postfrontal does not form the border of the upper temporal fenestra
      According to Wikipeida: “Dinosauria is … diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus. https://en.wikipedia.org/wiki/Evolution_of_dinosaurs. IMHO, The postrrontal and postorbital are fused in dinosaurs.

      Can we work a little harder to find an outgroup for the Pterosauria, Neil? Note that Eoraptor, like many archosaurs has a tiny manual digit 4 and tiny to absent pedal digit 5. Use logic. Look for a pterosaur sister with a long manual digit 4 and a long pedal digit 5, among a long list of other traits documented above. Take off your blinders, Neil. Cognitive dissonance is a powerful human mental state. My experience with you suggests you will avoid accepting the obvious in order to hold on to your beliefs. Scientists don’t do this. Scientists are willing to concede when evidence stacks up against their feelings.

      • All of your claims relate to your interpretations of Cosesaurus, Sharovipteryx, and Longisquama, obtained through DGS or similar tracing strategies. That is the irreproducible methodology I was referring to. Saller carefully looked at specimens, scored their traits, and let software determine relationships. The only thing he didn’t use was DGS. Can you find a scientifically sound and peer-reviewed study which supports your claim that DGS is a reliable methodology? Because your readers are only getting your opinion on the subject. They deserve better.

        I brought up Christopher Bennett’s insights into the mandibular fenestra (or lack thereof) in pterosaurs when corresponding with you. You still seem to be under the impression that the Austriadraco mandible is exposed in medial view, despite evidence to the contrary. I recommend that you look into his 2015 study (published since your “debunking”) more closely.

        My arguments are based on a phylogenetic analysis using data obtained using reliable methodologies. Yours are based on a phylogenetic analysis using data obtained from a methodology of your own design (DGS), which other scientists have yet to consider reliable. Which of us sounds more logical considering our methods?

      • Neil, you decided to trust Saller’s written description without tracings over my written description with the testable evidence of precise tracings. DGS is nothing more than tracing using color for clarity instead of outline. Tracing is nothing new, so don’t pretend it is voodoo. Tracing is the only way to convey and interpret to readers precisely what is in the fossil. Saller failed to do that. You are reading Saller’s words and imagining everything else with your own personal bias. That is the unsound method. The test for this hypothesis is to change Saller’s name for mine. Let’s imagine Saller had produced precise tracings of a specimen 7 years ago and I came along as a PhD student and declared that I could not see what Saller had traced using the methods you support. Now who do you believe?

        I am sorry that you fell for the propaganda. It is time to grow up and become a scientist.

      • One further thought… since Saller included no pterosaurs as taxa, I’m guessing he included no pterosaur traits in his character list. You tell me. If not, then did you really give it a fair test?

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