Updated ‘Origin of Dinosaurs and Birds’ YouTube video

When I first posted a video on YouTube
featuring the origin of dinosaurs and birds several years ago, the large reptile tree (LRT, 1611+ taxa) had 500 some taxa and the video featured genera going all the way back to Devonian tetrapods. That far back was unnecessary and became outdated last year with the addition of more tetrapods to the LRT. I will do the same with the other videos as time allows.

And one more thing…
as the late Steve Jobs used to say. The above pterosaur video was updated, as well, to be more concise and informative.

Best regards
and thank you for your readership.

New PBS Eons video: How pterosaurs got their wings

The good folks at PBS Eons
added a new video on the origin of pterosaurs. The following repeats (with added images) my comments on the PBS Eons video on YouTube.

This video is SO WRONG
so many times. The origin of pterosaurs is not ‘foggy.’

The Scleromochlus (Fig. 1) hypothesis for pterosaur origins was invalidated by Peters 2000 who tested it and all other candidates for pterosaur origins in four separate phylogenetic analyses by adding taxa to prior studies. Macrocnemus, Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama (Fig. 2) were recovered closer to pterosaurs.
Figure 3. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Figure 1. Short-legged Gracilisuchus, along with sisters, long-legged bipedal Pseudhesperosuchus and Scleromochlus.

Scleromochlus nested with basal bipedal crocodylomorphs,
(Fig. 1) close to the origin of dinosaurs. Note the tiny hands on Scleromochlus. Note the lack of pedal digit 5 on Scleromochlus. By contrast, pterosaurs had large hands and a specialized pedal digit 5 that had two large phalanges that folded together such that the distal phalanx was dorsal side down, making an impression behind pedal digits 1–4 (Figs. 10, 11). More on this below.
Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Figure 2. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx. Click to enlarge.

Pterosaurs didn’t fossilize very well?
False. Look at all the excellent pterosaur fossils we know of, some with soft tissue.
Pterosaurs are not archosaurs.
Peters 2000 introduced the clade Fenestrasauria for pterosaurs + their above named ancestors. These in turn were part of a new clade of lepidosaurs, named Tritosauria, nesting between Rhynchocephalians and Protosquamates published in Peters 2007.
Cosesaurus and Longisquama have extra-large fingers,
dominated by digit 4. See: http://reptileevolution.com/pterosaur-wings.htm
Ornithodirans are a junior synonym
for Reptilia (=Amniota, see cladogram link below). Not wise to bring up this invalidated clade name.
Figure 1. Scaphognathians to scale. Click to enlarge.

Figure 3. Scaphognathians to scale. Click to enlarge.

The pterodactyloid grade of pterosaur
was attained four times by convergence (two from the genus Dorygnathus, two more from the genus Scaphognathus, Fig. 3). Transitional taxa were all tiny Solnhofen forms (Fig. 3). As in many other clades, phylogenetic miniaturization attended the genesis of derived pterosaurs.
As in giant birds,
Quetzalcoatlus (Fig. 4) grew so large because it was flightless. All azhdarchids over six-feet-tall had clipped wings (vestigial distal wing phalanges) good for flapping and walking on, not for flying.
Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 4. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

No pterosaur fossils had wing membranes extending ‘the length of their legs’.
All soft tissue shows the short chord wing membrane was stretched between the elbow and wing tip.  See: http://reptileevolution.com/pterosaur-wings.htm
Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Figure 5. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

How did pterosaurs get their wings? 
Convergent with theropods ancestral to birds, Cosesaurus reorganized its pectoral girdle to flap (Fig. 5). The scapula became immobile and strap-like. The coracoid became immobile and stalk-like. The clavicles, interclavicle and single sternum migrated together, then fused together. The forelimbs of Cosesaurus were too short for flight, but fully capable of flapping, probably as a mating ritual. Likewise the pectoral girdles of Sharovipteryx and Longisquama were similarly built. Of the three, Longisquama had the largest hands, but still could not fly. Bergamodactylus was the basalmost pterosaur and it could fly. See links below.
Why guess how a hypothetical ancestor learned to fly
when we have excellent samples of every stage? (see links below)
The arboreal leaping model
does not require flapping — and gliders do not evolve into flappers (e.g. colugos, squirrels, sugar gliders, etc.)
The arboreal parachute model
worked for bats, but they were seeking prey beneath their perches as fingers 3-5 then 2-5 elongated. Pterosaurs only elongated one digit: #4. It made a better wing than bug-in-the-leaf-litter trap.
The terrestrial model
is Lamarckian, growing bigger wings to catch insects just out of reach for most is not good science.
Figure 5. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna.

Figure 6. Cosesaurus forelimb with pro to-aktinofibrils trailing the ulna.

Sexy
The valid hypothesis for bird and pterosaur wing evolution is competitive attractiveness during mate selection (think birds-of-paradise) with cosesaur-like creatures flapping and displaying. BTW, both Cosesaurus and Longisquama are preserved with membranes trailing finger 4, (Fig. 6) which folds in the plane of the wing in Longisquama (Fig. 7).

Figure 7. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Not to be outdone,
Sharovipteryx (Fig. 8) had membranes (uropatagia) trailing each hind limb. These are reduced in pterosaurs, which continue to use their hind limbs as horizontal stabilizers, their feet as twin rudders, as the flapping forelimbs, closer to the center of gravity, become ever larger, better for display, then for short flapping hops, then for flight.
Figure 3. Sharovipteryx reconstructed. Note the flattened torso.

Figure 8. Sharovipteryx reconstructed. Note the flattened torso.

Another false statement corrected here:
The scapula of Scleromochlus (Fig. 1) was tiny. It only had to support a tiny forelimb with vestigial fingers.
Scleromochlus had a ‘square pelvis’
because it, too was a biped. But that was nothing compared to the larger pelvis of Cosesaurus (Fig. 9), which also had a prepubis, a pterosaurian trait not found on Scleromochlus. The pelvis of Sharovipteryx was larger still.
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 9. Cosesaurus flapping. Tere should be some bounce in the tail and neck, but that would involve more effort and physics.

Scleromochlus had a long muscular tail.
As in crocs and dinos, and most reptiles, the caudofemoral muscles were pulling the femur. Compare that with the attenuated tail of pterosaurs, Cosesaurus and Sharovipteryx. Only pelvic muscles were pulling the femur.
Back legs longer than front legs in Scleromochlus?
That’s what we also see in Cosesaurus, Sharovipteryx and Longisquama.
Cosesaurus and Rotodactylus, a perfect match.

Figure 10. 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).

Walking on its toes?
We have Rotodactylus ichnites (hand and footprints, Figs. 10, 11) that match Middle Triassic Cosesaurus in the Early Triassic. These include the impression of pedal digit 5 behind toes 1-4. Nothing else like them in the fossil record.
True!
Scleromochlus was like the modern jerboa, with its tiny vestigial hands, totally inappropriate as a pterosaur ancestor.
False!
Not all pterosaur tracks are quadrupedal. Only derived pterosaurs, those that frequented beaches were. We have bipedal pterosaur tracks (Fig. 12). See references below.
Cosesaurus foot in lateral view matches Rotodactylus tracks.

Figure 11. Cosesaurus foot in lateral view matches Rotodactylus tracks.

Quadrupedality in pterosaurs is secondary.
Note the backward pointing manual digit 3 in quad tracks. Note the fusion of four to thirteen sacrals into a sacrum and the elongation of the ilium to anchor large femoral muscles and anchor the increasingly larger sacrum in all pterosaurs. In order to flap, you have to be a biped.
Figure 1. Pteraichnus nipponensis, a pterosaur manus and pes trackway, matched to n23, ?Pterodactylus kochi (the holotype), a basal Germanodactylus.

Figure 12. Pteraichnus nipponensis, a pterosaur manus and pes trackway, matched to n23, ?Pterodactylus kochi (the holotype), a basal Germanodactylus.

All quad pterosaurs can be attributed to pterodactyloid-grade pterosaurs,
those that underwent phylogenetic miniaturization during the Jurassic. At that time, the fly-size hatchlings of the hummingbird-sized adults (Fig. 13) could not leave the moist leaf litter or risk desiccation until growing to a sufficient size. So they walked around on all fours until attaining flight size.
A hypothetical hatchling No. 6

Figure 2. A hypothetical hatchling No. 6 alongside a fly, a flea and the world’s smallest insect, a fairy fly (fairy wasp). The fairy wasp is shown enlarged here (scaled in red) and in figure 1.

True!
The extinction of pterosaurs can be attributed to their great size at the end of the Cretaceous. They had no tiny representatives, like they did at the end of the Jurassic, to weather the rapid climate changes and/or seek shelter.

References

For a cladogram that documents the family tree of pterosaurs see: http://ReptileEvolution.com/MPUM6009-3.htm
For a cladogram that documents pterosaur and dinosaur ancestors back to Silurian jawless fish see: http://ReptileEvolution.com/reptile-tree.htm
For fossils and reconstructions of pterosaur ancestors, see:
And here are all the peer-reviewed academic publications
that some pterosaur experts don’t want to talk about:
Peters D 2000a. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2000b. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141.

Testing for bipedalism in archosaurs (and pterosaurs)

Grinham, VanBuren and Norman 2019
looked at the origin of bipedalism in the archosaur and pre-archosaur ancestors of birds.

They report, “We test whether facultative bipedality is a transitionary state of locomotor mode evolution in the most recent early archosaur phylogenies using maximum-likelihood ancestral state reconstructions for the first time. Across a total of seven independent transitions from quadrupedality to a state of obligate bipedality, we find that facultative bipedality exists as an intermediary mode only once, despite being acquired a total of 14 times. We also report more independent acquisitions of obligate bipedality in archosaurs than previously hypothesized, suggesting that locomotor mode is more evolutionarily fluid than expected and more readily experimented with in these reptiles.”

The authors used the cladograms of Ezcurra 2016 and Nesbitt 2011,
both of which are riddled with inappropriate taxon inclusion and exclusion problems as reported earlier here and here. Therefore comparisons regarding the number of times obligate bipedality in archosaurs occurred is useless lacking a consensus phylogenetic contaxt. In the large reptile tree (LRT, 1542 taxa) bipedality occurs only once in archosaurs. It just precedes the origin of the archosaurs (crocs + dinos only). Ezcurra, Nesbitt and Grinham et al. include a long list of inappropriate taxa in their inclusion set according to the LRT that skews results (e.g. the lepidosauromorphs: Jesairisosaurus, Macrocnemus, Mesosuchus, Gephyrosaurus, Planocephalosaurus, Eudimorphodon, Dimorphodon).

Grinham, VanBuren and Norman 2019
follow Nesbitt 2011 who listed the pterosaurs Eudimorphodon and Dimorphodon as archosauriforms. Grinham et al. 2017 considered both to be quadrupeds without explanation. The only pterosaur paper cited by Grinham et al. is Padian 2008. Peters 2007 recovered pterosaurs with lepidosaurs like Huehuecuetzpalli, later validated, expanded and published online in LRT. Peters 2000, 2011 reported on bipedal pterosaur tracks and restricted most cited pterosaur ichnites to flat-footed beach-combing pterosaur clades. Use keyword “bipedal pterosaur tracks” in the SEARCH box to see prior samples of digitigrade and bipedal tracks reported by this blogpost along with their citations.

Padian 2008 reported
“Peters (2000) also reached the conclusion that pterosaurs were not ornithodirans, and found instead that they were nested within what is traditionally considered the Prolacertiformes. It remains to be seen whether other workers can duplicate this result, but a recent analysis by Hone and Benton (2007) failed to find support for Peters’ analyses. For the present, because five different analyses have found that pterosaurs are ornithodirans, and the systematic community seems to have largely accepted this, the present paper will proceed with this provisional conclusion, without discounting other possible solutions.”

We looked at the bogus results
of Hone and Benton 2007 earlier here. They dropped taxa proposed as pterosaur ancestors by Peters 2000 because their inclusion would have tilted their supertree toward the topology recovered by Peters 2000, who tested four previously published cladograms by adding novel taxa to them. One year earlier than Peters 2000, co-author Benton 1999 had proposed Scleromochlus as a pterosaur sister/ancestor, which Peters 2000 invalidated. Evidently professor Benton did not appreciate that and succeeded, at least in Padian’s eyes, to dismiss Peters 2000 as an unacceptable and suppressible minority view.

Note that none
of Padian’s “five different analyses” used novel taxa proposed by Peters 2000. Padian’s report, “The systematic community seems to have largely accepted this,” demonstrates that Padian and his community were adverse to testing the novel taxa of Peters 2000 on their own terms, preferring the cozy comfort of tradition and orthodoxy — and they did this after Peters 2000 invalidated earlier efforts simply by adding a few taxa. Very easy to do. Even today it remains impossible to explain the origin of pterosaurs as archosaurs in a phylogenetic context because they are not archosaurs. In the world of academics, taxon exclusion remains a useful tool. We should all fight against this practice.

Later Padian 2008 reports, 
“Alternatively, if we consider that pterosaurs evolved from quadrupedal basal archosauromorphs such as Prolacertiformes (Peters, 2000), a rather different model of limb evolution must be proposed. In prolacertiforms the humerus is longer than the forearm and the femur is longer than the tibia; the glenoacetabular length is also long, as in most terrestrial quadrupeds. To attain the proportions seen in basal pterosaurs, the relative lengths of humerus and forearm and of femur and tibia would have to have been reversed, and the vertebral column would have had to shorten considerably (or the limb segments increase). These changes are independent of the extensive reorganization of the joints for erect posture and parasagittal gait, for which there is no evidence so far in prolacertiforms.”

Figure 1. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Note: Padian 2008 chose to ignore the limb proportions
of Longisquama (Figs. 1, 2) another taxon proposed by Peters 2000 with a humerus shorter than the forearm, as in pterosaurs. He also ignored Sharovipteryx, another taxon proposed by Peters 2000, with a femur shorter than the tibia. In the world of academics, taxon exclusion remains a useful tool. We should all fight against this.

Padian 2008 also chose to ignore the evidence for bipedalism
in Cosesaurus (Fig. 2) matching facutatively bipedal Rotodactylus tracks (Peters 2000) and Sharovipteryx (Fig. 2), an obligate biped based on proportions. Both have the short torso relative to the limb length sought for and purposefully overlooked by Padian 2008 (see above quotation). In the world of academics, taxon exclusion remains a useful tool. We should all fight against this.

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

Figure 2. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Students of paleontology:
I’m sorry, this is just the way it is.

Getting back to bipedalism in archosaurs,
the LRT, subset Fig. 4) documents the patterns and possibilities of bipedal locomotion in taxa preceding dinosaurs. The topology here employs more taxa, pushes pterosaurs over to lepidosaurs (Peters 2007) and nests only Crocodylomorpha + Dinosauria within the Archosauria. Poposauria is the proximal outgroup. This is where bipedalism in archosaurs first appeared. Other bipedal taxa achieved this ability by convergence. Secondary quadrupedalism occurred several times in archosaurs, and by convergence in certain derived pterosaurs (e.g. ctenochasmatids and azhdarchids), as evidenced by their backward pointing manual digit 3 in ichnites.

Figure 3. Subset of the LRT focusing on the archosauromorph synapsid-grade taxa and diapsid-grade taxa with color added to bipedal taxa.

Figure 3. Subset of the LRT focusing on the archosauromorph synapsid-grade taxa and diapsid-grade taxa with color added to bipedal taxa.

As documented here and elsewhere
It does not matter if certain hypotheses are peer-reviewed and published or not.
Academic authors can choose to omit pertinent taxa and papers knowing that ‘friendly’ academic referees and editors will likewise choose to overlook such omissions. Apparently all academics seek and work to maintain the orthodox line, no matter how invalid it may be.

That’s why this blogpost and ReptileEvolution.com came into being.
We’re talking about hard science. Ignoring and omitting hard evidence cannot be tolerated or coddled. I ask only that academic workers rise to the professionalism they seek to inspire in their own students. History will put this all into perspective. Professional legacies may end up in shame unless they take action soon. Just test the taxa. 


References
Benton MJ 1999. Scleromochlus taylori and the origin of the pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf
Ezcurra MD 2016 The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4, e1778. (doi:10.7717/peerj.1778)
Grinham LR, VanBuren CS and Norman DB 2019. Testing for a facultative locomotor mode in the acquisition of archosaur bipedality. R. Soc. open sci. 6: 190569. http://dx.doi.org/10.1098/rsos.190569
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Nesbitt SJ 2011. The early evolution ofArchosaurs: relationships and the origin of major clades. Bull. Am. Museum Nat. Hist. 352, 1–292. (doi:10.1206/352.1)
Padian K 2008. Were pterosaur ancestors bipedal or quadrupedal? Morphometric,
functional, and phylogenetic considerations. Zitteliana R. B Abhandlungen der Bayer.
Staatssammlung fur Palaontologie und Geol. 28B, 21–28.
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 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

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

Pterosaur pycnofibres revisited: Yang et al. 2018

Yang et al. 2018 bring us a closer look
at pterosaur integumentary structures (= pycnofibres, pycnofibers) courtesy of Tom Kaye and his fluorescence technique,

From the abstract
These findings could imply that feathers had deep evolutionary origins in ancestral archosaurs, or that these structures arose independently in pterosaurs.”

The latter is true and has been known for years. 
Filament structures arose in the lepidosaur fenestrasaur ancestors of pterosaurs, including Cosesaurus, Sharovipteryx (Fig. 1) and Longisquama (Fig. 2). None of these are archosaurs. The archosaur hypothesis for pterosaur origins has failed to produce even one taxon with pterosaur synapomorphies that is not trumped by taxa first specified in Peters 2000 or more recently improved in the large reptile tree at ReptileEvolution.com, which includes pterosaur ancestors extending back to basal lepidosaurs, basal reptiles and Devonian tetrapods.

The problem is co-author Professor Michael Benton
doesn’t want pterosaurs to be derived from fenestrasaurs. The Yang et al. paper insisted that pterosaurs are archosaurs and members of the invalid Benton invented clade, Avemetatarsalia.

You might remember,
Professor Benton and Professor David Hone wrote a two-part set of papers (Hone and Benton 2007, 2009) that declared they would test two competing hypotheses of pterosaur origins Peters 2000 (fenestrasaurs) vs. Bennett 1996 (archosaurs). The second paper (2009) dropped all references to Peters 2000, deleting the taxa therein and falsely ascribed the now gutted hypothesis to Bennett 1996. Ultimately they were unable to find any ancestors for pterosaurs. That’s because they omitted them on purpose.

Figure 1. Sharovipteryx cervicals surrounded by filaments.

Figure 1. Sharovipteryx cervicals surrounded by filaments.

Why?
Benton (1999) declared tiny-fingered Scleromochlus was the nonviolent sister to pterosaurs and evidently Benton wanted to maintain that charade. That’s where he erected the invalid clade, Avemetatarsalia, which makes several appearances in Yang et al. 2018. Peters 2000 is not cited in Yang et al. 2018.

Longisquama in situ. See if you can find the sternal complex, scapula and coracoid before looking at figure 2 where they are highlighted.

Figure 2. Longisquama in situ. The bones are hard to see here due to filaments and skin, especially visible in the throat area.

True to S. Christopher Bennett’s curse,
“You will not get published and if you do get published you won’t be cited.” And that’s why I publish here, online, where I can respond immediately when something gets published that includes taxon exclusion. This is the dark underbelly of paleontology. Sorry that I had to show you this.

References
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoological Journal of the Linnean Society 118:261-308.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2009. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Yang et al. (8 co-authors including Benton MJ) 2018. Pterosaur integumentary structures with complefeather-like branching. Nature ecology & evolution

The origin of pterosaurs delayed…

In Peters 2000
pterosaurs were found to be indisputably derived from the fenestrasaurs, Longisquama, Sharovipteryx and Cosesaurus in order of increasing distance.

In Peters 2007
pterosaurs (and other fenestrasaurs) were found to be indisputably derived from a new clade of lepidosaurs, including Huehuecuetzpalli.

In Peters 2011–2018
more taxa (up to 1253 at last count) cemented those relationships. Other works, cited below, further cement those relationships.

Switek 2018 reported,
“We’ve cataloged plenty of species, with more named every year, but understanding how they [pterosaurs] fit into the Mesozoic world has eluded us.”

This, dear readers,
is called suppression. Perhaps Dr. SC Bennett (personal communication) said it best, “You won’t get published and if you do get published, you won’t be cited.” What other science is like this?

Dr. J. Ostrom, famous for his bird origin work, lamented the same problem. 
According to the Hartford Courant (2000), “In 1973, Ostrom broke from the scientific mainstream by reviving a Victorian-era hypothesis (see above) that his colleagues considered far-fetched: Birds, he said, evolved from dinosaurs. And he spent the rest of his career trying to prove it.” 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!’” Ostrom was the first scientist to collect physical evidence for the theory. Ostrom provoked a debate that raged for decades. “At first they said, `Oh John, you’re crazy,”’ Ostrom said in 1999.”

So, it’s not just me. It’s paleontology.
For readers thinking about getting into this field, here’s fair warning. And I’m going to call it out every time I see it, just like John Ostrom did.

References
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. 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141.http://dx.doi.org/10.1080/10420940.2011.573605
Peters D 2011–2018. ReptileEvolution.com and PterosaurHeresies.Wordpress.com
Switek B. 2018. https://blogs.scientificamerican.com/laelaps/digging-into-pterosaur-diets/

Hartford Courant (2000)

Origin of pterosaurs and origin of archosauriforms abstracts

Part 2 
The following manuscripts are independently published online without peer-review at the DavidPetersStudio.com website. http://www.davidpetersstudio.com/papers.htm

Better to put them out there this way
than to let these works remain suppressed. Hope this helps clarify issues.


Peters D 2018c.
Cosesaurus avicepsSharovipteryx mirabilis and Longisquama insignis reinterpreted
PDF of manuscript and figures

Currently the majority of pterosaur and archosaur workers maintain the traditional paradigms that pterosaurs appeared suddenly in the fossil record without obvious antecedent and that pterosaurs were most closely related to archosaurs because they shared an antorbital fenestra and a simple hinge ankle. Oddly, these hypotheses continue despite the widely accepted acknowledgement that no archosauriformes document a gradual accumulation of pterosaurian traits. The minority view provided four phylogenetic analyses that documented a gradual accumulation of pterosaurian traits in three fenestrasaurs, Cosesaurus aviceps, Sharovipteryx mirabilis, and Longisquama insignis and their ancestors. These three also had an antorbital fenestra and a simple hinge ankle by convergence. Unfortunately the minority view descriptions also included several misinterpretations. Those are corrected here. The revised descriptions add further support to the nesting of pterosaurs with fenestrasaurs, a clade that now nests within a new clade of lepidosaurs between Sphenodontia and Squamata. The new data sheds light on the genesis of active flapping fight in the nonvolant ancestors of pterosaurs.


Peters, D. 2018d
Youngoides romeri and the origin of the Archosauriformes

Prior workers reported that all specimens attributed to Youngopsis and Youngoides could not be distinguished from the holotype of Youngina capensis. Others considered all specimens attributed to ProterosuchusChasmatosaurus and Elaphrosuchus conspecific. In both cases distinct skull shapes were attributed to taphonomic variations due to distortion pressure or allometric growth. Here a large phylogenetic analysis of the Amniota (1248 taxa) tests those hypotheses. The resulting tree recovers a den of small Youngina specimens preceding the Protorosauria. Another specimen nests at the base of the Protorosauria. Six others nest between the Protorosauria and the Archosauriformes. The most derived of these bears a nascent antorbital fenestra. Two other putative Youngina specimens nest at unrelated nodes. In like fashion, the various specimens assigned to Proterosuchus are recovered in distinct clades. One leads to the Proterochampsidae, Parasuchia and Choristodera. The latter lost the antorbital fenestra. Another clade leads to all higher archosauriforms. The present analysis reveals an evolutionary sequence shedding new light on the origin and radiation of early archosauriforms. Taphonomic distortion pressure and allometry during ontogeny were less of a factor than previously assumed. The splitting of several specimens currently considered Youngina and Proterosuchus into distinct genera and species is supported here.


These manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1251 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.

Bergamodactylus (basal pterosaur) back ‘under the microscope’

This all started with Kellner 2015
who proposed 6 states of pterosaur ontogeny based on skeletal fusion of discrete elements. This hypothesis was tested in phylogenetic analysis and shown to be invalid. Pterosaurs don’t fuse bones during ontogeny. Fusion appears in phylogenic patterns. Oblivious to this fact, Dalla Vecchia 2018 dismissed Kellner’s hypothesis by writing, “Kellner’s six ontogenetic stages are an oversimplification mixing ontogenetic features of different taxa that probably had distinct growth patterns. Finding commonality across all pterosaurs is impossible, because there is much variation in pterosaur ontogeny and the available sample is highly restricted.” 

Neither Kellner nor Dalla Vecchia recognize
the lepidosaurian affinities of pterosaurs, and do not realize that as lepidosaurs pterosaurs mature differently than archosaurs. Some lepidosaurs continue growing after fusing elements (Maisano 2002). Others never fuse elements. Fusion of elements in pterosaurs is phylogenetic, not ontogenetic. Pterosaurs mature isometrically, not allometrically as proven by every full-term embryo and every known juvenile among a wide variety of pterosaur specimens. Plus, all of the small purported Solnhofen juveniles phylogenetically nest as key transitional taxa linking larger long-tail primitive pterosaurs to larger short-tail derived pterosaurs (Peters 2007). That’s how those clades survived the extinction events that doomed their fellow, larger, longer-tailed kin.

Kellner 2015 also
distinguished a small pterosaur MPUM 6009 from the holotype of Eudimorphodon and from Carniadactylus (MFSN 1797, Dalla Vecchia 2009; Fig. 1) and gave MPUM 6009 the name Bergamodactylus (Fig. 1) after Peters 2007 had done the same (without renaming MPUM 6009), in phylogenetic analysis. Neither Kellner nor Dalla Vecchia performed a phylogenetic analysis, but preferred to describe similar bones. That rarely works out well.

Figure 1. Bergamodactylus compared to Carniadactylus. These two nest apart from one another in the LRT.

Figure 1. Bergamodactylus (MPUM 6009) compared to Carniadactylus (MFSN 1797). These two nest apart from one another in the LRT. Contra Dalla Vecchia 2018, these two share relatively few traits in common. The feet, cervicals, sternal complex coracoids and legs are different.

Dalla Vecchia 2018 concludes, 
“The anatomical differences between MPUM 6009 and MFSN 1797 are too small to support the erection a new genus for MPUM 6009.” That is incorrect (Fig. 1). Several taxa nest between these two taxa in the large pterosaur tree (LPT, 232 taxa). Their feet alone (Fig. 1) were shown to be very different in Peters (2011).

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

Figure 2. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

From the Dalla Vecchia 2018 abstract
“Six stages (OS1-6) were identified by Kellner (2015) to establish the ontogeny of a given pterosaur fossil. These were used to support the erection of several new Triassic taxa including Bergamodactylus wildi, which is based on a single specimen (MPUM 6009) from the Norian of Lombardy, Italy. However, those ontogenetic stages are not valid because different pterosaur taxa had different tempos of skeletal development. Purported diagnostic characters of Bergamodactylus wildi are not autapomorphic or were incorrectly identified. Although minor differences do exist between MPUM 6009 and the holotype of Carniadactylus rosenfeldi, these do not warrant generic differentiation. Thus, MPUM 6009 is here retained within the taxon Carniadactylus rosenfeldi as proposed by Dalla Vecchia (2009a).” \

Dalla Vecchia is basing his opinion on comparing a few cherry-picked traits, possibly convergent, rather than running both taxa and a long list of other pterosaurs through phylogenetic analysis, to see where unbiased software nests both taxa among the others.

Plus, as mentioned above, both authors are working from an antiquated set or rules that no longer apply now that pterosaurs have been tested and validated as lepidosaurs.

Figure 2. Bergamodactylus skull colorized with DGS and reconstructed.

Figure 3. Bergamodactylus skull colorized with DGS and reconstructed. Palatal and occipital bones shown here were missed by Dalla Vecchia 2018 and prior workers who did not use DGS.

Phylogenetic analysis
employing a large gamut of taxa, like the large reptile tree (LRT, 1215 taxa), invalidates traditional arguments that pterosaurs arose without obvious precedent among the archosauriforms, which most pterosaur workers, including both Kellner and Dalla Vecchia, still cling to, despite no evidence of support. Pterosaurs arose from fenestrasaur tritosaur lepidosaurs (Fig. 7).

Figure 4. The skull of Bergamodactylus traced by Kellner 2015, Dalla Vecchia 2018 and by me using DGS.

Figure 4. The skull of Bergamodactylus traced by Kellner 2015, Dalla Vecchia 2018 and by me using DGS. See figure 2 for a reconstruction of the DGS tracing.  Prior authors missed all the palatal and occipital bones along with several others.

The metacarpus of Bergamodactylus
has a few disarticulated elements. When replaced to their in vivo positions the axial rotation of metacarpal 4 (convergent with the axial rotation of pedal digit 1 in birds) enables the wing finger to fold in the plane of the hand, not against the palmar surface. Manual digit 5, a vestige, goes along for the ride, rotating the dorsal surface of the hand (Fig. 5).

Figure 5. Metacarpus of Bergamodactylus (MPUM 6009) in situ and reconstructed.

Figure 5. Metacarpus of Bergamodactylus (MPUM 6009) in situ and reconstructed. Apparently the pteroid splintered apart, overlooked by those with direct access to the specimen. The distal carpals are not co-ossified, as they are in later pterosaurs. The laterally longer fingers, up to digit 4, is a tritosaur trait. Note ungual 1 lies on top of the posterior face of metacarpal 4. That was overlooked by those who had direct access to the specimen, which supports the utility of DGS.

 

Bergamodactylus, as the most basal pterosaur,
is itself a transitional taxon bridging non-volant fenestrasaurs with all other pterosaurs. And the wing (Fig. 6) was about the last thing to evolve.

Figure 6. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Bergamodactylus to scale
with Cosesaurus and Longisquama (Fig. 7), demonstrate the variety within the Fenestrasauria. Pterosaurs arose more or less directly from a sister to Cosesaurus (based on overall proportions), but note that both Sharovipteryx and Longisquama have more pterosaurian traits than Cosesaurus does. This pattern is convergent with that of birds, of which several clades of Solnhofen bird descendants arose of similar yet distinct structure.

Figure 8. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus.

Figure 7. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus.

See rollover images
of Bergamodactylus in situ here. You’ll see how DGS is able to pull out post-cranial details overlooked by others in the chaos and confusion of layers of bones and impressions in MPUM 6009. Cranial details are best seen in figure 3 above, which is based on higher resolution images.

References
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus gen. n. rosenfeldi (Dalla Vecchia, 1995). Riv. It. Paleontol. Strat., 115: 159-186.
Dalla Vecchia FM 2018. Comments on Triassic pterosaurs with a commentary on the “ontogenetic stages” of Kellner (2015) and the validity of Bergamodactylus wildi.  Rivista Italiana di Paleontologia e Stratigrafia 124(2): 317-341. DOI: https://doi.org/10.13130/2039-4942/10099 https://riviste.unimi.it/index.php/RIPS/article/view/10099
Kellner AWA. 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais Acad. Brasil. Ciênc., 87(2): 669-689.
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.
Peters D. 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

The soft underbelly of a phylogenetic analysis

Here’s another rejection letter
that sees things the way the editors want to see it, not the way things need to be seen. I post these reviews and replies because someday you may want to publish a paper yourself and you need to see what editors are willing to say and do to keep, in this case, the origin of pterosaurs a mystery, and to keep amateurs from embarrassing the academic community by reporting that all they need do is add a few more relevant taxa.

Associate Editor Comments:

The intro: “The manuscript argues for a hypothesis that places Longisquama, Sharovipteryx, Cosesaurus, and a small number of other taxa as being especially closely related to pterosaurs, with their respective morphologies informing the long sought-after origin of characteristic pterosaur traits. The manuscript quite correctly identifies its preferred hypothesis as a minority viewpoint, lamenting the fact that its previous versions continue to be widely ignored by other pterosaur and archosaur workers. The hypothesis is based on a phylogenetic analysis of 231 multistate characters and 1090 taxa — from which the tree topology of 24 taxa relevant to the arguments of the paper were figured and discussed. The results of the entire analysis are available only on the author’s website and to my knowledge have never been published in a peer-reviewed platform.” That will change when one editor and one reviewer let the work see publication, but apparently not on this editor’s watch. 

Where the teeth are bared: “It is an understatement to say that these results differ significantly from those of other studies, with every major reptile clade, as typically recognized, being extensively paraphyletic.” All clades presented in the LRT are monophyletic and fully resolved. This editor is working from an old textbook. Taxon exclusion led to errors in prior studies. This can be readily checked by simply adding taxa and checking that all taxa document a gradual accumulation of derived traits in competing cladograms. That’s why the large reptile tree is so large, to minimize taxon exclusion problems that plague smaller studies. 

There is only one way to get published: “The author states that his character matrix is not really drawn from existing studies but rather was “largely built from scratch.” One could interpret this as an admirable attempt to shed the existing assumptions that burden other studies, but ultimately this hypothesis will never overturn existing paradigms until it demonstrates that it better explains the totality of the existing data. This study certainly does not do that. Simply disregarding a large percentage of the characters that the larger community of workers has decided are important for resolving reptile phylogeny in favor of those the author deems relevant is never going to accomplish this goal.” See below.

Sidenote: “The criticisms of the author’s approach by Hone and Benton 2007 still appear to be relevant – at least they have never been directly addressed, nor are they addressed in this manuscript.” Yes, they are. Hone and Benton excluded the fenestrasaur taxa that overturn the pterosaur origin question in Peters 2000, after promising to test them. Why is every paleo colleague afraid of Cosesaurus (the subject of the submitted manuscript)?

Case closed: “Until the author explicitly demonstrates why the characters he omits should not be included or how adding taxa and characters to an existing matrix, such as that found in the Nesbitt (2011) study, produces the promoted tree topology, I cannot recommend publishing this work or sending it out for further review.”  Problem 1: Nesbitt’s 2011 paper was on archosauriforms. Pterosaurs were thrown into that study, but they are not archosauriforms, as documented 11 years earlier. Problem 2: Adding taxa or characters to an existing matrix assumes the existing matrix is faultless. It is not. Nesbitt 2011 suffers from some inappropriate taxon inclusion and a great deal of taxon exclusion, along with some bad scoring that we looked at in a nine-part series ending here. Problem 3: Peters 2000 added taxa to four prior phylogenetic analyses and recovered the same results each time. None of those four were built on prior analyses. Now let’s move forward 11 years. Why was Nesbitt 2011 published when it mentioned, but did not include relevant taxa reported by Peters 2000? Editors and referees let that pass. Why? Have the rules changed?

Evidently it matters who the author is, and how well they are connected in the academic community, not how well a project is researched.

Editors and referees are only human. They have an agenda and a world view, like everyone does. They see what they want to see, comment on what they want to comment on and maintain whatever status quo they currently follow. How do we know this in this case? Note how little was said in this review (not one sentence) about the new pterosaur traits found in Cosesaurus, which formed the subject of this paper.

My reply:

Dear [Editors]:

Thank you for your kind reply and review.

Ultimately the number of characters or their publication history means little, since one set of two hundred characters will result in the same tree topology as another set of two hundred characters. The character list is the soft underbelly of any analysis, the part editors and reviewers go to when they cannot argue against the demonstrated gradual accumulation of derived traits shown by the included taxa, universally excluded from other studies that include pterosaurs. 

Maintaining the majority view will only keep the origin of pterosaurs in the dark. 

Best regards,

References
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.
Peters D 2000b. A reexamination of four prolacertiforms with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293–336.