Cosesaurus vs. Saller 2016 part 2

Yesterday we looked at
some typically and recently overlooked pterosaur traits in Cosesaurus, a lepidosaur, tritosaur, tanystropheid, fenestrasaur taxon that nests as a pterosaur outgroup in the large reptile tree (LRT, 1401 taxa). Saller 2016 reported a lack of pterosaur traits in his examination of Cosesaurus beneath a microscope. Since Cosesaurus is so small, lacks bones and is printed as a negative in the matrix (holes become bumps), this specimen is best viewed on a computer monitor after dozens of close-ups have been taken using various angles of lighting to bring out one detail or another.

Today we’ll finish examining Cosesaurus
by taking a DGS look at the extremities and soft tissue. GIF animations trace what I see and allow you to see (or not see) pertinent impressions in the grainy matrix.

Figure 1. Cosesaurus skull frills and gular sac.

Figure 1. Cosesaurus skull frills and gular sac. I did not trace all the dorsal frills. Perhaps you’ll see several more near the base of the skull.

First a little backstory

Yang et al. 2018 considered pterosaur plumage/fibers homologous with dinosaur/bird feathers—but only by omitting fenestrasaurs like Cosesaurus, Sharovipteryx and Longisquama (Fig. 9), all of which preserve feathery/hairy fibers covering their bodies. We looked at that issue here. At the end of that post, it is worthwhile to review what several pterosaur experts opined on that issue. None reminded us that Cosesaurus and kin were closer relatives of pterosaurs, developing extradermal membranes and plumage by convergence, though all were aware of this hypothesis of relationships.

Figure 2. Cosesaurus nasal crest (in yellow).

Figure 2. Cosesaurus nasal crest (in yellow).

Figure 3. Cosesaurus dorsal frill. This frill evolves into giant plumes on another Cosesaurus descendant, Longisquama.

Figure 3. Cosesaurus dorsal frill. This frill evolves into giant plumes on another Cosesaurus descendant, Longisquama. Image from Ellenberger 1993. This appears to  be a fluorescing image.

The dorsal frill of Middle Triassic Cosesaurus
(Figs. 3, 9) finds its greatest expression in Late Triassic Longisquama (Fig. 9), which was named for its long plumes. The relationship Cosesaurus has with Longisquama has also been largely ignored for the last twenty years.

Figure 4. Cosesaurus uropatagium. This trait is recorded on pterosaurs, Sharovipteryx and Longisquama.

Figure 4. Cosesaurus uropatagium. This trait is recorded on pterosaurs, Sharovipteryx and Longisquama. As in Sharovipteryx some fibers extend anteriorly the femur. See if you can see them without my help.

The twin uropatagia of Middle Triassic Cosesaurus
predates similar extradermal membranes on Late Triassic Sharovipteryx and all pterosaurs (even Sordes, which has been traditional and mistakenly given a single uropatagium spanning both hind limbs, disconnected from the tail). Note the uropatagium extend to p5.1 in Cosesaurus, to p5.2 in the obligate biped, Sharovipteryx, and only the tarsus in pterosaurs, which have a much smaller set of uropatagia, but a larger set of forelimb wings.

Figure 5. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna.

Figure 5. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna. DGS enables the tracing of each hand on a segregated/separate Photoshop layer.

Saller 2016
reported none of these tissues and declared that he could see no pterosaur traits in Cosesaurus. This was picked up by the author of the Wikipedia Cosesaurus page as the latest thinking on this specimen, even though it actually represents only one PhD candidate’s opinion. See how important it is to at least attempt to color trace what one sees on a computer monitor? Some things are just too jumbled and/or too subtle to be ‘seen’ by an eyeball or through a microscope. The DGS method, like cladistic analysis, forces one to thoroughly examine and dissect the data into tiny discrete and segregated bits that can be later analyzed and compared.

Figure 6. Cosesaurus hind limbs. The upper one is exposed on the fossil. The lower one is preserved beneath the medusa. The tarsals are not displaced in the latter.

Figure 6. Cosesaurus hind limbs. The upper one is clearly exposed on the fossil (see Figure 4). The yellow dot is a fossilized air bubble. The lower one is preserved beneath the medusa. The tarsals are not quite as displaced in the latter.  These pedes match occasionally bipedal Rotodactylus tracks.

You decide
whether or not these various soft tissues are present in Cosesaurus. I present and interpret the data. All discoveries must be confirmed or refuted by others.

Figure 7. Cosesaurus forelimb fibers. These indicate the pterosaur wing originated distally, as in bird feathers, not as a bat-like membrane arising from the torso.

Figure 7. Cosesaurus forelimb fibers. These indicate the pterosaur wing originated distally, as in bird feathers, not as a bat-like membrane arising from the torso.

Dorsal frills are elaborated
in Longisquama. Uropatagia are elaborated in Sharovipteryx. Aktinofibrils are elaborated in pterosaurs like Bergamodactylus, which is similar in size to Cosesaurus (Fig. 8). These indicate the pterosaur wing originated distally (Peters 2002), as in bird feathers, not as a bat-like membrane arising from the torso.

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

Figure 8. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Figure 9. The origin of pterosaurs from tanystropheid ancestors now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx. Click to enlarge.

Remember
this data was submitted for publication, but rejected, as this hypothesis of relationships continues to be ignored and rejected by pterosaur workers content with the status quo supported by taxon exclusion. That’s why PterosaurHeresies and ReptileEvolution.com continue to document discoveries and post updates nearly every day for the past seven years.


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.
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 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
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.
Yang et al. (8 co-authors) 2018. Pterosaur integumentary structures with complex feather-like branching. Nature ecology & evolution doi:10.1038/s41559-018-0728-7

wiki/Cosesaurus

Peters D xxxx. Unpublished paper on Cosesaurus, Sharovipteryx and Longisquama on ResearchGate.net

2 thoughts on “Cosesaurus vs. Saller 2016 part 2

  1. I’m wondering whether you have checked the preservational circumstances of other Alcover/ Mont-ral fossils. Just to make sure that the “soft tissue” you identify is not caused by taphonomic processes relating to the sedimentation. Have you looked into the various fish and marine reptile fossils from that area to see whether the same strands of sediment or lighting alterations occur there as well?

    Hemleben & Freels (1977) heavily discussed the geological setting of the area, including notes on preservational circumstances. It’s all in German, but you can copy and paste the text from researchgate into google translate: https://www.researchgate.net/publication/235677840

    • Good question, Jake. Fortunately Dr. Ellenberger already did so in his 1993 tome, which I reference and cherish. It is good to remember on this point that a jellyfish is stuck to Cosesaurus. Jellyfish are nothing but soft tissue, so that’s a confidence builder. In addition, given the bone data and a wide gamut phylogenetic analysis, phylogenetic bracketing indicates that Cosesaurus should have many of the traits identified above. Given that starting point, the more people that see this specimen under various lighting conditions, the better, so long as they put in the required efforts.

      The alternative, of course, is to ignore every taxon between Huehuecuetzpalli and Longisquama, which is what workers do when they add pterosaurs to archosaur studies. And do they find suitable outgroups for pterosaurs when they do that? Everyone admits the answer is no.

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