Cosesaurus pelvis slightly deeper after review

Nothing is known of the pterosaur ancestor,
Cosesaurus aviceps (Figs. 1, 2), except an exquisite mold that preserves an impression of its bones and soft tissue — along with the softest of soft tissue: a jellyfish also impressed into the matrix (the blob in Fig. 1), and a few trapped air bubbles.

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 2. 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. Shown here larger than life size. See figure 1.

Mold fossils are interesting.
Shadows and highlights are the only data. By rotating the light and viewing angle some bones appear and others disappear. So, you need to see such fossils from several angles.

Figure 1. CLICK TO ENLARGE. Cosesaurus reconstructed with enlarged parts of interest including a pes (foot) matching a Rotodactylus track. Here the pelvis is reconstructed according to figure 3. Shown here about life-size.

Figure 1. CLICK TO ENLARGE. Cosesaurus reconstructed with enlarged parts of interest including a pes (foot) matching a Rotodactylus track. Here the pelvis is reconstructed according to figure 3. Shown here about life-size.

Yesterday
I reexamined a photo of the pelvis and sacral vertebrae of Cosesaurus. I suspected the pubis and ilium were actually deeper than I previously thought. That hunch paid off (Figs. 3, 4) as DGS tracings showed edges of the pubis and ischium peeking out from both sides of other overlapping bones, sometimes rotated from their original positions.

Figure 3. Cosesaurus pelvic area in situ. Colors added in layers. See figure 4 for reconstructing the slightly scattered and overlapping elements.

Figure 3. Cosesaurus pelvic area in situ. Colors added in layers. See figure 4 for reconstructing the slightly scattered and overlapping elements. Red elements are displaced gastralia.

When both pelves matched
that confirmed the new interpretations.

Figure 4. Pelvis and sacral vertebrae from figure 3 reconstructed.

Figure 4. Pelvis and four sacral vertebrae from figure 3 reconstructed. The deeper ischium permits the passage of larger eggs. More than two sacral vertebrae are indicators of bipedal locomotion. Cosesaurus pedes match occasionally bipedal Rotodactylus tracks (Fig. 2).

These new reconstructions and orientations
also more closely match both ancestral and descendant taxa (Fig. 5). These corrections are but a few of the over 100,000 corrections made during the last ten years. The LRT is getting better and better with every improvement like this.

Figure 5. Origin and evolution of the prepubis in tritosaurs.

Figure 5. Origin and evolution of the prepubis in tritosaurs.

Cosesaurus aviceps
(Ellenberger and DeVillalta 1974; Ladinian, upper Middle Triassic ~230 mya, ~16cm long), was originally considered an ancestor of birds, then a juvenile Macrocnemus (Sanz and López-Martinez 1984) and finally an ancestor of pterosaurs (Peters 2000a, b; 2009).

Here Cosesaurus was derived from a sister to Huehuecuetzpalli and, more proximally, BES SC 111Cosesaurus was a basal fenestrasaur that phylogenetically preceded SharovipteryxLongsiquama and pterosaurs. This is a hypothesis that pterosaur workers with PhDs have avoided for the last twenty years. For reasons only they know, other paleo workers have preferred to report, “We don’t know where pterosaurs came from” or “pterosaurs are the closest relatives of dinosaurs.” Those who make their living from delivering traditional lectures and selling traditional textbooks have been suppressing this information.


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 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
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.

wiki/Cosesaurus
reptileevolution.com/reptile-tree.htm

 

Pre-pterosaur skull evolution

Pterosaurs are chiefly known by their post-cranial traits.
Here (Fig. 1) a diagram is presented of pterosaur ancestor skulls in phylogenetic order. Alongside this diagram is a list of general trends documented from the tritosaur lepidosaur, Huehuecuetzpalli (at top), to Macrocnemus to Cosesaurus to Longisquama and culminating with the basal pterosaur, Bergamodactylus (at bottom).

Figure 1. Skulls of pterosaur ancestors from Huehuecuetzpalli through Macrocnemus, Cosesaurus, Longisquama and the pterosaur Bergamodactylus.

Figure 1. Skulls of pterosaur ancestors from Huehuecuetzpalli through Macrocnemus, Cosesaurus, Longisquama and the pterosaur Bergamodactylus.

Huehuecuetzpalli never fits well
into traditional squamate cladograms because it is not a member of the Squamata.

Earlier we looked at the gradual evolution
of the manus in these taxa (Fig. 2). You won’t find evidence like this ‘out there’ in the academic literature where PhDs continue to say, “We still don’t know the ancestors to pterosaurs.” This is rather embarrassing for them, if not now, then someday.

pterosaur wings

Figure 2. Click to enlarge. The origin of the pterosaur wing and whatever became of manual digit 5?

Addendum: originally published online on Facebook yesterday:
For my paleo friends… this is Cosesaurus (Fig. 3), a lepidosaur, not closely related to living lizards, that was able to run bipedally, like some living lizards do by convergence. It had sprawling limbs, but created a narrow gauge trackway matching Early to Middle Triassic Rotodactylus footprints found from Europe to North America. Lateral toe (#5) uniquely bent back to imprint dorsal side down behind the other four regular toes.

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 3. Click to enlarge and animate. Cosesaurus flapping – fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

The curved, stem-like, immobile coracoid is an indicator of flapping (birds share this trait), matched to a strap-like scapula (birds share this trait). The interclavicle overlaps the sternum and clavicles to create a pre-sternal complex, as in pterosaurs. A tiny pterosaur-like prepubis is present. So is an anterior projection of the ilium (top pelvic bone) typically found only in bipeds. Two wrist bones migrated to the thumb side of the wrist to create a pteroid and preaxial carpal, otherwise only found in pterosaurs (but similar, by convergence, to the panda’s ‘thumb’). The tail is extremely narrow and stiff.

Extradermal membranes extend from the crest of the skull to the back of the pelvis. Fibers (pre-wings) trail the forelimbs. A membrane trails each hind limb. These and many other traits are shared with pterosaurs, the flying reptiles of the Mesozoic.

Like birds, pterosaur ancestors used their decorative traits (feathers, membranes) for display, including flapping prior to being able to fly. Running bipedally enabled breathing while running (something quadrupedal undulating lizards cannot do). Bipedal locomotion increased stamina and warmed up the metabolism. So secondary sexual traits (decorations and behavior for display) helped create both birds and pterosaurs.

I studied the one-of-a-kind fossil, a hand-sized mold of such exquisite detail that it also preserved a small jellyfish, in Barcelona in the 1990s where it was inappropriately wrapped in a few layers of toilet paper. In 2000 I described Cosesaurus as an ancestor to pterosaurs, and did so by adding it to four previously published phylogenetic analyses.

Unfortunately, that peer-reviewed and academically published paper has been ignored ever since, for reasons I still cannot fathom other than I have no science degree, let alone a PhD. To this day paleontologists repeat the phrase, “We still don’t know where pterosaurs come from.” Frustrating, but I’ve gotten used to it. I guess this posting is just a chance to vent.

For more exquisite Cosesaurus details, click here: http://reptileevolution.com/cosesaurus.htm

Oculudentavis in more incredible detail! (thanks to Li et al. 2020)

Li et al. 2020 bring us
higher resolution scans of the putative tiny toothed ‘bird’ (according to Xing et al. 2020) Oculudentavis (Fig. 1). Following a trend started here a week ago, Li et al. support a generalized lepidosaur interpretation, but then tragically overlook/deny details readily observed in their own data (Fig.1).

FIgure 1. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Colors applied here.

FIgure 1. CT scan model from Li et al. 2020, who denied the presence of a quadratojugal and an antorbital fenestra, both of which are present. Colors applied here. The previously overlooked jugal-lacrimnal suture becomes apparent at this scale and presentation.

Li et al. deny the presence of a clearly visible antorbital fenestra.
They report, “One of the most bizarre characters is the absence of an antorbital fenestra. Xing et al. argued the antorbital fenestra fused with the orbit, but they reported the lacrimal is present at the anterior margin of the orbit. This contradicts the definition of the lacrimal in birds, where the lacrimal is the bone between the orbit and antorbital, fenestra. In addition, a separate antorbital fenestra is a stable character among archosaurs including non-avian dinosaurs and birds, and all the known Cretaceous birds do have a separate antorbital fenestra.”

Contra Li et al.
a standard, ordinary antorbital fenestra is present (Fig. 1 dark arrow) and the lacrimal is between the orbit and antorbital fenestra. This is also the description of the antorbital fenestra and fenestrasaurs, like Cosesaurus (Fig. 2), Sharovipteryx and pterosaurs (Peters 2000).

Li et al. report,
“The ventral margin of the orbit is formed by the jugal.”

Contra Li et al.
the lacrimal is ventral to half the orbit (Fig. 1). The jugal is the other half. The suture becomes visible at the new magnification.

Li et al. report,
“Another unambiguous squamate synapomorphy in Oculudentavis is the loss of the lower temporal bar.” 

Contra Li et al.
the lower temporal bar is created by the quadratojugal, as in Cosesaurus, Sharovipteryx and pterosaurs. In Oculudentavis the fragile and extremely tiny quadratojugal is broken into several pieces. DGS (coloring the bones) enables the identification of those pieces (Fig. 1).

Figure 2. Cosesaurus nasal crest (in yellow).

Figure 2. Cosesaurus with colors applied. Compare to figure 1.

Li et al. conclude,
“Our new morphological discoveries suggest that lepidosaurs should be included in the phylogenetic analysis of Oculudentavis.” 

Contra Li et al.
these are all false ‘discoveries’.

Also note that Li et al. cannot discern
which sort of lepidosaurs should be tested in the next phylogenetic analysis of Oculudentavis. That’s because lepidosaur tritosaur fenestrasaurs, like Cosesaurus (Fig. 2), are not on their radar. That’s because pterosaur referees have worked to suppress the publication of new data on Cosesaurus and kin. And that’s what scientists get for not ‘playing it straight.’


References
Li Z, Wang W, Hu H, Wang M, Y H and Lu J 2020. Is Oculudentavis a bird or even archosaur? bioRxiv (preprint) doi: https://doi.org/10.1101/2020.03.16.993949
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

wiki/Oculudentavis

 

Did Oculudentavis have an antorbital fenestra?

Some say: Yes.
Others say: No.

You decide. 
Here are two CT scans (Figs. 1, 2), one from the left and the other from the right with overlays interpretating skull sutures, enlarged from the previous presentation.

Figure 1. CT scan from Xing et al. 2020, colors added to show antorbital fenestra. Note the wrinkling of the maxilla reacting to the twisting of the tiny, fragile skull during taphonomy.

Figure 1. CT scan from Xing et al. 2020, colors added to show antorbital fenestra. Note the wrinkling of the maxilla (green) reacting to the twisting of the tiny, fragile skull during taphonomy.

Now, perhaps, you can see the difficulty
in determining whether or not an antorbital fenestra was present in Oculudentavis. DGS makes things easier by segregating bones with color. All interpretations are up for discussion. I hope you’ll agree, DGS overlays facilitate such discussions better than line tracings do.

Figure 1. CT scan of Oculudentavis from Xing et al. 2020, colors added. Antorbital fenestra here is mailer than in Cosesaurus, but still visible.

Figure 2. CT scan of Oculudentavis from Xing et al. 2020, colors added. Antorbital fenestra here is mailer than in Cosesaurus, but still visible.

The antorbital fenestra
in Cosesaurus (Fig. 3) and Oculudentavis (Figs. 1, 2) is only one trait among many linking these basal members of the Fenestrasauria with derived members in the Pterosauria. No single trait is ‘key’. Between the Middle Triassic (Cosesaurus) and the Early Cretaceous (Oculudentavis) the antorbital fenestra could have grown larger, as it did in pterosaurs, or disappear entirely. It’s only one trait. No one trait is that important in a phylogenetic analysis that includes 238 traits.

Figure 2. Cosesaurus nasal crest (in yellow).

Figure 3. Cosesaurus nasal crest (in yellow).

Some workers doubt
that Cosesaurus (Fig. 3) had an antorbital fenestra. Again, you decide. The large reptile tree  (LRT, 1656+ taxa) nests Cosesaurus basal to pterosaurs and other fenestrasaurs.

Final thought:
With cosesaurs in the Early Cretaceous, it might seem possible to spawn a second origin for pterosaur-like flyers… but that never happened. Only in the Middle Triassic were genes and environs in lock-step with one another to produce basal pterosaurs.


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.
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
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.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

wiki/Oculudentavis
wiki/Cosesaurus

You heard it here first: Others also doubt the theropod affinities of Oculudentavis

The now famous tiny skull in amber, Oculudentavis, 
(Fig. 1; Xing et al. 2020) continues as a topic of conversation following its online publication in Nature and two previous PH posts here and here.

Figure 1. Oculudentavis in amber much enlarged. See figure 2 for actual size.

Figure 1. Oculudentavis in amber much enlarged.

Several workers have also thrown cold water
on the tiny theropod affinities of Oculudentavis. Oddly, all seem to avoid testing or considering in their arguments the sister taxon in the large reptile tree (LRT): Cosesaurus (Fig. 2). Instead, they report on what Oculudentavis is not. Examples follow:

Dr. Andrea Cau writes in TheropodaBlogspot.com Link here (translated from Italian using Google translate): 

“I believe that the interpretation proposed by Xing et al. (2020) is very problematic. Oculudentavis in fact has numerous anomalous characteristics for a bird and even for a dinosaur. And this makes me doubt that it is classifiable within Dinosauria (and Avialae).

  1. Absence of anti-orbital window. [not true, click here]
  2. Quadrate with large lateral concavity. This character is not typical of dinosaurs, but of lepidosaurs. [that quadrate is twisted, the other is not, the concavity is posterior in vivo]
  3. The maxillary and posterior teeth of the maxilla extend widely below the orbit.
  4. Dentition with pleurodont or acrodont implant.
  5. Very large post-temporal fenestra.
  6. Spoon-shaped sclerotic plates is typical of many scaled lepidosaurs.
  7. Coronoid process that describes a posterodorsal concavity of the jaw reminds more of a lepidosaur than a maniraptor.
  8. Very small size comparable to those of the skulls of many small squamata found in Burmese amber.

“In conclusion, there are too many “lizard” characters in Oculudentavis not to raise the suspicion that this fossil is not a bird at all, let alone a dinosaur, but another type of diapsid, perhaps a scaled lepidosaur, if not possibly a specimen very immature than some other Mesozoic group (for example, a Choristodere). It is well known that many types of reptiles present in the final stage of embryonic development and in the very first moments after hatching a cranial morphology similar to the general one of birds (of in fact, the bird skull is a form of “infantilization” of the classic reptilian skull, extended to the adult).
Unfortunately, the authors, while noting some of the similarities with the squamata, do not test the affinities of Oculudentavis outside Avialae.

“PS: out of curiosity, I tested Oculudentavis in the large Squamata matrix by Gauthier et al. (2012): it turns out to be a stem-Gekkota.”

Note to readers: Neither Gauthier et al. 2012 nor Dr. Cau tested fenestrasaurs, like Cosesaurus… yet another case of taxon exclusion. With regard to phylogenetic age, fenestrasaur tritosaur lepidosaurs, like Oculudentavis, hatch with the proportions of adults (ontogenetic isometry), so the ontogenetic status of this taxon needs further context (e.g. coeval larger adults or smaller hatchlings)/

Update March 14, 2020:
Readwer TG (below) informs me that Cau’s study did include Cosesaurus. My reply follows: “Thank you, Tyler. Good to know. My mistake. Strange that his Oculudentavis has traits more like the distinctively different Sphenodon and Huehuecuetzpalli, when it looks more like Cosesaurus in every regard. Here’s a guess based on experience: neither he nor Gauthier went to Barcelona to see Cosesaurus, and neither did either reference or cite Peters 2000 or the ResearchGate.net update. And Cau probably used the Xing et al. 2020 ink tracing of Oculudentavis rather than the more detailed DGS tracing I produced (or he could have traced himself), since he did not see the tiny antorbital fenestra [or the twisted quadrate]. Just a guess based on 20 years of experience.” 

PS. Neither Gauthier nor Cau showed their work (e.g. skulls diagrammed with suture interpretations as shown at ReptileEvolution.com links). Therefore we cannot know if or where mistakes were made in their scoring attempts. In a similar fashion, testing revealed a raft of scoring problems with Nesbitt 2011, covered earlier here in the last of a nine-part series. 

Dr. Darren Naish updates his original post in Tetrapod Zoology  
with the following notes:

“A number of experts whose opinions I respect have expressed doubts about the claimed theropod status of the fossil discussed below and have argued that it is more likely a non-dinosaurian reptile, perhaps a drepanosaur or lepidosaur (and maybe even a lizard). I did, of course, consider this sort of thing while writing the article but dismissed my doubts because I assumed that – as a Nature paper – the specimen’s identity was thoroughly checked and re-checked by relevant experts before and during the review process, and that any such doubts had been allayed. At the time of writing, this proposed non-dinosaurian status looks likely and a team of Chinese authors, led by Wang Wei, have just released an article [not linked] arguing for non-dinosaurian status. I don’t know what’s going to happen next, but let’s see. The original, unmodified article follows below the line…”

We can only trust what Dr. Naish reports regarding his private doubts as to the affinities of Oculudentavis. Here he confesses to assuming the ‘opinions’ of ‘relevant experts’ got it right, like all the other journalists who reported on this discovery, rather than testing the hypothesis of Xing et al. 2020, like a good scientist should.

While we’re on the subject of confessing, 
earlier the LRT nested Oculudentavis with Cosesaurus (Fig. 1) despite the former’s much later appearance and derived traits, like the essentially solid palate. I failed to mention the skull of Oculudentavis shares just a few traits with another Late Triassic fenestrasaur, Sharovipteryx (Fig. 1). If Oculudentavis also had a slender neck, like the one in Sharovipteryx, perhaps that was one reason why only the skull was trapped in pine sap, later transformed into amber. Just a guess.

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration.

Figure 2. Cosesaurus was experimenting with a bipedal configuration according to matching Rotodactylus tracks and a coracoid shape similar to those of flapping tetrapods. Long-legged Sharovipteryx was fully committed to a bipedal configuration.

Note:
with locked down and elongate coracoids, all members of the clade Fenestrasauria were flapping like flightless pterosaurs. Appearing tens of millions of years after the Middle Triassic genesis of fenestrasaurs, who knows what sort of post-crania tiny Early Cretaceous Oculudentavis may have evolved! Known clade members already vary like Hieronymus Bosch fantasy creatures.

The LRT is a powerful tool for nesting taxa
while minimizing taxon exclusion. And it works fast. Feel free to use it in your own studies.


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.
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.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. 
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

late arrival:

Wang Wei, Zhiheng Li, Hu Yan, Wang Min, Hongyu Yi & Lu Jing 2020. The “smallest dinosaur in history” in amber may be the biggest mistake in history. Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences: Popular Science News (2020/03/13)
http://ivpp.cas.cn/kxcb/kpdt/202003/t20200313_5514594.html

from B. Creisler’s translated post at dml.cmnh.org:

“Here is the list of problems found by the authors:
Doubts 1. Can the shape of the head prove that it is a bird? 
Doubt 2. Unreasonable Phylogenetic Analysis 
Doubt 3. Birds without antorbital fenestrae? 
Doubt 4. “Birds” with pleurodont teeth? 
Doubt 5. Mysterious quadratojugal bone 
Doubt 6. Scleral bones only found in lizards 
Doubt 7. The bird with the most teeth in history? 
Doubt 8. Body size 
Doubt 9. No feathers? 
Doubt 10. Strange wording and logic chains
We hope that the authors of the paper will respond publicly to these questions as soon as possible. At the same time, it is hoped that the authors of the paper will quickly release the raw data of CT scans, so that other scientists can verify the existing results based on the raw data.”
July Post-Script
Authors retract the paper, according to Nature.

 

Oculudentavis: not a tiny bird or dinosaur. It’s a tiny cosesaur lepidosaur.

Figure 1. Oculudentavis in amber much enlarged. See figure 2 for actual size.

Figure 1. Oculudentavis in amber much enlarged from Xing et al. 2020. See figure 2 for actual size.

I never thought the tiny Middle Triassic pterosaur ancestor, Cosesaurus
(Fig. 2, 4) would ever be joined by an Early Cretaceous sister taxon that was even smaller. Yesterday the impossible happened when the editors of Nature published a description of tiny Oculudentavis (Xing et al. 2020; Figs. 1, 2; Early Cretaceous, 99 mya; 1.4cm skull), which the authors mistakenly considered a basal bird with teeth and the smallest Mesozoic dinosaur.

Figure 2. CT scans of Oculudentavis from Xing et al. 2020 and colored here, plus a comparison of Cosesaurus to scale.

Figure 2. CT scans of Oculudentavis from Xing et al. 2020 and colored here, plus a comparison of Cosesaurus to scale.

Taxon exclusion
Unfortunately the authors did not test Oculudentavis with Cosesaurus, a fenestrasaur, tritosaur lepidosaur… a taxon far from dinosaurs. When Oculudentavis was added to the large reptile tree (LRT) as the 1656th taxon, the tree length was 20291.

As a test
I forced Oculudentavis over to the London specimen of Archaeopteryx, which Xing et al. recovered as a sister, and the LRT bumped up to 20324, a mere 33 steps more despite the huge phylogenetic distance.

I’ve said it before,
convergence is rampant in the tetrapod family tree.

To that point, it should be remembered,
the original describers of Cosesaurus (Ellenberger and de Villalta 1974) mistakenly considered it a Middle Triassic stem bird.

In contrast,
Peters (2000) recovered Cosesaurus and kin with pterosaurs using four previously published phylogenetic analyses. Later, with more taxa, Peters (2007) recovered pterosaurs and kin with the lepidosaur Huehuecuetzpalli (Fig. 3). In addition, ResearchGate.net holds an unpublished manuscript and figures redescribing Cosesaurus and kin much more accurately. The pterosaur referees did not want that manuscript published, having ignored the earlier ones for so long.

Figure 3. Oculudentavis added to the LRT.

Figure 3. Oculudentavis added to the LRT with previously untested  tritosaur lepidosaurs.

Ironically
Xing et al. noted in tiny Oculudentavis lepidosaur-like sclerotic (eyeball) bones and acrodont to pleurodont teeth extending below the orbit, as in modern lizards. Even with these clues, they did not add lepidosaurs to their analysis. They assumed from the start they had a tiny dinosaur-bird (with lepidosaur traits).

Figure 2. Cosesaurus running and flapping - slow.

Figure 4. Cosesaurus running and flapping. If you want to know what the Oculudentaivis post-crania looks like, this is the closest known sister taxon, slightly smaller than full scale.

Distinct from Cosesaurus,
(Fig. 2) the palate of Oculudentavis is solid below the rostrum. The antorbital fenestra is reduced. Damage to the skull displaced one ectopterygoid to the mid palate and broke the jugal. The post-crania remains unknown, but Cosesaurus (Fig. 4) is the most similar taxon.

From the Xing et al. 2020 abstract:
“Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)—the smallest living bird—in size. The O. khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology9 that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology.”

The authors saw lepidosaur traits not found in basal birds/tiny dinosaurs.
Rather than seeking and testing more parsimonious sister taxa elsewhere, the authors chose to follow their initial bias and described their find as an odd sort of tiny bird.

In a similar fashion
just a few days ago Hone et al. 2020 did much the same as they mistakenly described a large pteryodactylid, Luchibang, as a small istiodactylid, following their initial bias.

The LRT provides a wide gamut of 1656 taxa 
to test your next new taxon. Don’t make the same mistake as the above authors by assuming your odd little something is something it isn’t.


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.
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.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. 
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

Thanks to Dr. O’Connor for sending a PDF of the Nature paper. 

wiki/Oculudentavis
www.researchgate.net

A pre-Cosesaurus: the BES SC111 specimen

Earlier
here and here we looked at the pterosaur traits found in the lepidosaur tritosaur fenestrasaur, Cosesauru aviceps (Fig. 1).

Today
let’s look at Cosesaurus traits found in the more primitive BES SC 111 specimen (Fig. 1) traditionally assigned to the larger set of specimens traditionally attributed to Macrocnemus (Fig. 2).

Traditional paleontologists
consider the BES SC111 specimen a juvenile based on its size and short rostrum relative to other Macrocnemus specimens. The large reptile tree (LRT, 1412 taxa) nests the BES SC111 specimen apart from Macrocnemus, basal to Langobardisaurus + Fenestrasauria. Since tritosaurs mature isometrically, juvenile Macrocnemus specimens should have adult proportions, but none are known at present.

Phylogenetic miniaturization
produce smaller tritosaur specimens with a shorter rostrum via neotony. Rather than juvenile traits, late stage embryo (= pre-hatchling) traits are retained into adulthood. Phylogenetic bracketing indicates the BES SC111 specimen was close to adult size.

Figure 1. The BES SC111 specimen attributed to Macrocnemus compared to Cosesaurus, the taxon transitional to pterosaurs. See text for detais.

Figure 1. The BES SC111 specimen attributed to Macrocnemus compared to Cosesaurus, the taxon transitional to pterosaurs. See text for detais.

Traits shared in the BES SC111 specimen and Cosesaurus:

  1. The skulls are virtually identical, including orbit size, antorbital fenestra, tooth size
  2. Torsos quite similar, both with many more gastralia than in ancestors
  3. Tail attenuated
  4. Interclavicle cruciform
  5. Sternum present
  6. Clavicles short, relatively straight and robust
  7. Scapula with longer posterior process (even longer in Cosesaurus)
  8. Metacarpal 4 is the longest, so is manual digit 4
  9. Ilium anterior process present (longer in Cosesaurus)
  10. Prepubis present (larger in Cosesaurus)
  11. Metatarsal 4 is the longest, so is pedal digit 4
  12. Metatarsal 5 is short
  13. Pedal 1.1 is elongate (longer in Cosesaurus)

Derived traits in Cosesaurus relative to BES SC111

  1. Overall smaller in Cosesaurus (neotony)
  2. Epipterygoid absent in Cosesaurus (neotony)
  3. Shorter neck in Cosesaurus (neotony)
  4. 5 sacrals in Cosesaurus (3 in BES SC111)
  5. Sternal complex in Cosesaurus with shifted elements
  6. Coracoid reduced to a curved stem in Cosesaurus (neotony, less ossification)
  7. Hand much larger in Cosesaurus (slightly longer than antebrachium)
  8. Centrale bones migrate to become preaxial carpal and pteroid in Cosesaurus
  9. Thyroid fenestra absent in Cosesaurus
  10. Pedal unguals rounded in BES SC111 
Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 2. Tanystropheus and kin going back to Huehuecuetzpalli. Cosesaurus is not shown here (see figure 1).

Due to convergence,
adding taxa is, perhaps, the only way to split protorosaurs (= prolacertiformes) from tritiosaurs. Make sure you add Huehuecuetzpalli (Fig. 2) to any such analysis.

Figure 3. BES SC111 pectoral region. Colors correspond to figure 1.

Figure 3. BES SC111 pectoral region. Colors correspond to figure 1. The left scapula(?) is incomplete. The interclavicle and sternum are largely hidden beneath the vertebrae. Not sure what that elliptical bone is at upper left and blue. It may be two.

The shifting of pectoral elements
from Huehuecuetzpalli to pterosaurs was detailed earlier here and here.

Figure 4. BES SC111 pelvic region. Colors correspond to those in figure 1. Note the tiny blue prepubes.

Figure 4. BES SC111 pelvic region. Colors correspond to those in figure 1. Note the tiny blue prepubes.

Several indicators of bipedal ability
are present in the BES SC111 specimen, as in the extant Chlamydosaurus kingii.

  1. Elongate ilium anterior process
  2. More than two sacral vertebrae
  3. Prepubes + stiff belly (more gastralia)
  4. Attenuated tail
  5. Elongate cervicals
Figure 6. Green iguana demonstrating the curling of pedal digit 5 in tendril-toed arboreal lepidosaurs, as hypothesized in the BES SC111 specimen and pterosaurs.

Figure 5. Green iguana demonstrating the curling of pedal digit 5 in tendril-toed arboreal lepidosaurs, as hypothesized in the BES SC111 specimen and pterosaurs.

Cosesaurus and Rotodactylus, a perfect match.

Figure 5. Cosesaurus and Rotodactylus, a perfect match. Elevate the proximal phalanges along with the metatarsus, bend back digit 5 and Cosesaurus (left) fits perfectly into Rotodactylus (right).

The curling of pedal digit 5
in the Rotodactylus trackmakers (Fig. 6) is a lepidosaur trait (Fig. 5) carried to extremes in basal pterosaurs, like ‘Sauria aberrante’ and Dimorphodon.


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 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Renesto S and Avanzini M 2002. Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy. Jahrbuch Geologie und Paläontologie, Abhandlung 224(1):31-48.
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. 

wiki/Cosesaurus
wiki/Macrocnemus

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

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