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 In addition, ResearchGate.net holds an unpublished manuscript and figures redescribing Cosesaurus and kin much more accurately.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

Lepidosaur bipedality and pelvis morphology: Grinham and Norman 2019

Grinham and Norman 2019
brings us a new look at 34 lepidosaur pelves with an emphasis on trends associated with bipedal locomotion. The authors illustrated 11 pelves (Fig. 1, white and yellow areas).
Figure 1. On the left, lepidosaur pelves from Grinham and Norman 2019, reordered phylogenetically here. On the right several tritosaur pelves and prepubes, most of which strongly demonstrate bipedal traits (elongate anterior ilium, increased sacral number). Yellow boxes indicate facultatively bipedal extant lepidosaurs.

Figure 1. On the left, lepidosaur pelves from Grinham and Norman 2019, reordered phylogenetically here. On the right several tritosaur pelves and prepubes, most of which strongly demonstrate bipedal traits (elongate anterior ilium, increased sacral number). Yellow boxes indicate facultatively bipedal extant lepidosaurs.

From the Grinham and Norman abstract:
“Facultative bipedality is regarded as an enigmatic middle ground in the evolution of obligate bipedality and is associated with high mechanical demands in extant lepidosaurs. Traits linked with this phenomenon are largely associated with the caudal end of the animal: hindlimbs and tail. The articulation of the pelvis with both of these structures suggests a morphofunctional role in the use of a facultative locomotor mode. Using a three-dimensional geometric morphometric approach, we examine the pelvic osteology and associated functional implications for 34 species of extant lepidosaur. Anatomical trends associated with the use of a bipedal locomotor mode and substrate preferences are correlated and functionally interpreted based on musculoskeletal descriptions. Changes in pelvic osteology associated with a facultatively bipedal locomotor mode are similar to those observed in species preferring arboreal substrates, indicating shared functionality between these ecologies.”
Unfortunately, Grinham and Norman omitted
tritosaur lepidosaurs from their study. In the Triassic many of them became bipeds and among these, pterosaurs achieved bipedalism supported with four, five and more sacral vertebrae between horizontally elongate ilia, convergent with dinosaurs. The addition of the prepubis virtually extended the anchorage for the puboischial muscles. After achieving flight, beach-combing pterosaurs reverted to a quadrupedal configuration with finger 3 pointing posteriorly. Giant Korean bipedal pterosaur tracks are best matched to large dsungaripterid/tapejarid clade taxa.
Unfortunately, Grinham and Norman reported,
“A recently published molecular-based time-calibrated phylogeny for Squamata was pared down to match the species in our dataset.” Their genomic cladogram bears little to no resemblance to the large reptile tree (LRT, 1635+ taxa), which tests traits, not genes. Once again, genes produce false positives. 
The authors’ principal component analysis of the pelvis failed 
to isolate bipedal lepidosaurs from the rest. Grinham and Norman reported, “The shape of the pelvis in facultatively bipedal extant lepidosaurs falls within the overall morphospace of lepidosaurs generally.” This is also visible in their illustrated pelves (Fig. 1). They also reported, However, it is generally found in a very concentrated area of that morphospace.” And Conclusions can be drawn regarding pelvic morphology and substrate use, although not with the same clarity as for locomotor mode.”
Grinham and Norman 2019 conclude,
“we have used 3D landmark-based geometric morphometrics to demonstrate that the overall morphospace for the lepidosaur pelvis is broad and wide-ranging. Within this overall morphospace, a small region is occupied by facultative bipeds. The vast majority of this smaller morphospace overlaps that occupied by species that show a preference for arboreal habitats. Pelvic morphological adaptations relevant for living in an arboreal environment are similar to those necessary to facilitate facultative bipedality.”
That’s interesting with regard to
the arboreal abilities of volant basal bipedal pterosaurs and their ancestors. Maybe next time Grinham and Norman will expand their study to include tritosaur lepidosaurs.

References
Grinham LR and Norman DB 2019. 
The pelvis as an anatomical indicator for facultative bipedality and substrate use in lepidosaurs. Biological Journal of the Linnean Society, blz190 (advance online publication) doi: https://doi.org/10.1093/biolinnean/blz190
https://academic.oup.com/biolinnean/advance-article-abstract/doi/10.1093/biolinnean/blz190/5687877Â
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Snyder RC 1954. The anatomy and function of the pelvic girdle and hind limb in lizard locomotion. American Journal of Anatomy 95:1-46.

Pterosaur prebubis

 

If Sharovipteryx was a glider, how did it climb trees with such tiny arms?

That’s a good question that is rarely asked.
Typically considered a hind-wing glider, Sharovipteryx (Sharov 1971) must have also been an obligate biped due to its proportions (Peters 2000). This is another form of locomotion rarely attributed to this Late Triassic Lepidosaur, Tritosaur Fenestrasaur. In the large reptile tree (LRT, 1413 taxa) Sharovipteryx was derived from a flapping, sprinting, occasionally bipedal Cosesaurus and Sharovipteryx shares many traits with pterosaurs (see below).

Today we’ll make comparisons
to an extant quadrupedal arboreal glider, Draco volans (Fig. 1).

Figure 1. Sharovipteryx alongside a photo of Draco volans. Both lepidosaurs had sprawling limbs, a long fifth toe, attenuated tail, extrademal membranes and dorsal ribs that flatten and widen its torso.

Figure 1. Sharovipteryx alongside a photo of Draco volans. Both lepidosaurs had sprawling limbs, a long fifth toe, attenuated tail and dorsal ribs that flatten and widen its torso.

Draco vs. Sharovipteryx: the similarities:

  1. sprawling limbs
  2. tendril-like toes and a long fifth toe
  3. attenuated tail
  4. dorsal ribs that flatten and widen its torso
  5. expandable hyoid for display

Draco vs. Sharovipteryx: the differences:

  1. extradermal membranes
  2. longer hind limbs (bipedal)
  3. shorter fore limbs
  4. longer cervical vertebrae
  5. 5+ sacral vertebrae
  6. longer ilia
  7. antorbital fenestra
  8. prepubes (phylogenetic bracketing)
  9. pteroid (former centrale) (Fig. 4)
  10. pedal 5.1 nearly as long as metatarsal 4 (Fig. 3)
  11. vestigial finger 5
  12. strap-like scapula
  13. stem-like coracoid (flapping)
  14. robust radius and ulna without interosseum space

Sharp-eyed readers will note
that many of the above traits are also found in pterosaurs.

Figure 2. Draco and Sharovipteryx bipedally on tree trunk, flapping its tiny arms. Hatchling Sharovipteryx between them.

Figure 2. Draco and Sharovipteryx bipedally on tree trunk, flapping its tiny arms. Hatchling Sharovipteryx between them. Several living birds are able to cling to tree trunks by their hind feet alone. Imagine the knees of Sharovipteryx bending even further, or imagine the femora further splayed to match the in situ fossil. Both configurations bring the body closer to the tree. As in pterosaurs, splayed knees can still produce a bipedal configuration because the knees bend the ankles back toward the midline.

Tradition presupposes that Sharovipteryx
was a glider. In counterpoint, Cosesaurus had uropatagia and was not a glider, but a flapping sprinter. Flapping animals do not become gliders. Gliders do not become flappers. Even so, it is good science to keep proposing alternatives for Sharovipteryx. Then we can refute, support or confirm all of the alternatives.

Tradition, in this case may be correct.
Cosesaurus
did not have membranes between its toes and it did not splay its metatarsals (Fig. 3). Nor did Cosesaurus have the limb proportions of Sharovipteryx and its several canard and strake neck membranes.

Figure 3. Sharovipteryx pes in dorsal and digit 4 in lateral view.

Figure 3. Sharovipteryx pes in dorsal and digit 4 in lateral view.

Dyke, Nudds And Rayner 2006
wrote, “Intriguingly, because of the incompleteness of the single known specimen, the evolutionary relationships of S. mirabilis remain poorly understood (Tatarinov, 1989; Unwin et al., 2001) – better preserved fossil material will be required to resolve this issue.” 

This paper followed and cited Peters 2000,
which added Sharovipteryx to four previously published phylogenetic analyses and found it nested with pterosaurs every time. It would have been so easy for Dyke, Nudds and Rayner to replicate the addition of taxa to the same four previously published analyses to confirm or refute Peters 2000. But evidently no PhD wants to confirm the work of another worker.

Later
Hone and Benton 2007, 2008 created a supertree to determine pterosaur affinities, but in the second of two papers removed all reference to Peters 2000 and removed Sharovipteryx from their taxon list.

In all prior studies
a lack of a precise tracing of the fossil and its counterpart is evidence that earlier studies did not look very closely or comprehensively at the fossil (see below).

I have seen Sharovipteryx first hand.
I keep in my file cabinet an 8.5×11-inch transparency for ready reference. The Sharovipteryx holotype fossil (Fig. 5) is nearly complete (but note the big gash in the middle) and, since I’ve actually done the phylogenetic work… well understood.

Figure 4. Sharovipteryx forelimb with digit 4 extended and flexed/folded. Note the large, deep unguals that appear to be useful, not vestigial.

Figure 4. Sharovipteryx forelimb with digit 4 extended and flexed/folded. Note the large, deep unguals that appear to be useful, not vestigial.

Dyke, Nudds And Rayner 2006
also proposed a delta-winged Sharovipteryx. They wrote, “Our novel interpretation of the bizarre flight mode of S. mirabilis is the first based directly on interpretation of the fossil itself and the first grounded in aerodynamics.” Students should be aware, not all such claims are valid. This claim, in particular, is built largely on imagination.

Figure 1. Sharovipteryx in situ. Click to enlarge. Here both plate and counter plate are shown along with a tracing based on both.

Figure 5. Sharovipteryx in situ. Click to enlarge. Here both plate and counter plate are shown along with a tracing based on both.

Hopefully the Dyke, Nudds And Rayner interpretation
will fade into the forgotten literature. The Dyke team fully imagined the forelimbs and added several membranes that are not present in the fossil while ignoring others that are present. So Dyke, Nudds and Rayner based their mathematics on an imaginary creature. We’ve seen how other scientists change/imagine morphology to fit their mathematical model. Despite the Dyke, Nudds and Rayner claim for first-hand observation, their cartoonish drawing of Sharovipteryx was based on Sharov’s freehand drawing.

What scientist concerned about their reputation would do this?
Well… Unwin, Alifanov and Benton (2003, yes Benton once again!) reprinted Sharov’s 1971 drawing, rather than create one of their own. Worse yet, Gans et al. 1987 created an even more cartoonish reconstruction, barely better than a cave drawing.

The takeaway:
As we’ve seen many times before, beware that certain PhDs sometimes do not put in the effort necessary to validate their claims. And sometimes PhDs, acting as referees, strive to ensure that contradicting hypotheses are not published.

Finally
Let’s not forget Kenneth Dial’s work with pre-volant bird chicks, able to climb steep inclines using everything they have to do it. (Video lecture 1 hour, 36 minutes).


References
Dyke GJ, Nudds RL and Rayner JMV 2006. Flight of Sharovipteryx mirabilis: the world’s first delta-winged glider. xx PDF
Gans C, Darevski I and Tatarinov LP 1987. Sharovipteryx, a reptilian glider? Paleobiology. 13: 415–426.
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.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Tatarinov LP 1989. [The systematic position and way of life of the problematic Upper Triassic reptile Sharovipteryx mirabilis.] Paleo. Zh. 1989(2): 110-112. [in Russian].
Unwin DM, Alifanov VR and Benton MJ 2003. Enigmatic small reptiles from the Middle-Late Triassic of Kyrgyzstan. In: Benton M.J., Shishkin M.A. & Unwin D.M. (Eds) The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge U. Press: 177-186.

http://reptileevolution.com/sharovipteryx.htm

A negative view of Cosesaurus

Glad to see this
…someone else has finally taken a good look at my favorite fossil.

Cosesaurus aviceps at close to actual size.

Figure 1. Cosesaurus aviceps at close to actual size. The blob next to it is a jelly fish. No actual bones are preserved. Cosesaurus is nothing but a deep impression faithfully preserving ever aspect of its skeleton down to the finest details. The tail is especially deep, which created the impression, when transferred to 2-D, of emanating feathers. Tomorrow the same image will be presented but flipped 180 degrees.

The one and only Cosesaurus 
is a negative mold (Figs. 1, 2) in matrix so sensitive to impressions that it also preserves a jellyfish (medusa). Here (Fig. 3) the skull of Cosesaurus was photographed by doctoral candidate, now Dr. Franco Saller, in his 2016 thesis on several Macrocnemus specimens.

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 negative mold (here lit from below to make it appear positive) that includes an amorphous blob, a jellyfish, that trapped one foot of this unique specimen.

Here
(Fig. 1) Adobe Photoshop software inverts the colors restoring the appearance of Cosesaurus as a positive impression, which makes it easier to interpret. Can you see the wispy cranial pycnofibers forming a crest over the orbit and antorbital fenestra?

Figure 1. GIF animation of Cosesaurus. Two frames, each five seconds long. The golden image is the negative mold in natural light. The blue image restores the appearance of a positive mold.

Figure 3. GIF animation of Cosesaurus. Two frames, each five seconds long. The golden image is the negative mold in natural light. The blue image restores the appearance of a positive mold.

Saller (p.148) wrote (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 anti-orbital 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. The analysis of the postcranial skeleton offers
however, very little space for this interpretation.”

That’s a rather short and unsupported dismissal, without phylogenetic analysis, for a taxon (Cosesaurus) with prepubes, an elongate ilium, four sacrals, the genesis of a sternal complex, a strap-like scapula, an stem-like coracoid, an attenuated tail, pycnofibers trailing the fore limbs, uropatagia trailing the hind limbs, a pteroid and preaxial carpal and a pedal digit 5.1 as long as a metatarsal, to name just a few traits that link Cosesaurus with pterosaurs.

Figure 2. Ironically, the Saller 2016 freehand reconstruction of Cosesaurus looks more like the pterosaur, Bergamodactylus, than the tracing by Peters of Cosesaurus. Yet Saller does not see the shared traits in Cosesaurus and pterosaurs.

Figure 4. Ironically, the Saller 2016 freehand reconstruction of Cosesaurus looks more like the pterosaur, Bergamodactylus, than the tracing by Peters of Cosesaurus. Yet Saller does not see or test for the shared traits in Cosesaurus and pterosaurs.

Saller presents a freehand reconstruction of the skull of Cosesaurus which I show alongside my own tracing of the skull of Cosesaurus and that of the basalmost pterosaurs, Bergamodactylus (Fig. 4). Ironically, his freehand sketch is more similar to Bergamodactylus than it is to my tracing of Cosesaurus in situ. See how dangerous freehand sketching can be? See how dangerous taxon exclusion can be?

Saller recognizes
the straight shape of the clavicles, long, thin scapulae and coracoids with an expanded articular portion, but fails to mention those are pterosaur traits not found in Macrocnemus. Saller recognizes the long preacetabular process of the ilium and the length of the hand exceeding the length of the forearm with compact metacarpals, but fails to mention those are pterosaur traits not found in Macrocnemus. Saller sees no carpals or distal phalanges on digit 4. Ellenberger and Peters both saw them earlier. Saller reports the tarsus “is not completely preserved,” but fails to mention fewer tarsals is a pterosaur trait not found in Macrocnemus. Saller reports the fifth metatarsal is, “as in the archosauromorpha, much shorter and expanded in a mediolateral direction to form a kind of a hook.” but fails to mention that’s the same shape and size seen in the lepidosaur, Huehuecuetzpalli, a taxon basal to Macrocnemus in the LRT… and also found in basal pterosaurs. Saller continues, “The first phalanx of the fifth finger is elongated and in appearance metapodial as in Tanystropheus, Langobardisaurus and Tanytrachelos,” but fails to mention those are pterosaur traits not found in Macrocnemus.

Among the other traits that Saller didn’t see,
Saller only saw two sacrals, but an elongate ilium can accommodate four.

Sad to see this
…doctoral students, now PhDs with their blinders on. Once again (remember Hone and Benton 2007 2009?), taxon exclusion is the main cause of the problems here. Why does this keep happening when the solution is just so damn simple? Add taxa to see what happens. That’s just good science.

And that’s why this blogpost exists:
To fact check those with their blinders on.

For those interested in a career in paleontology,
be prepared and look for disinformation like this. Sometimes it is not what they say, but what they should say and don’t say. 

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.
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

Cosesaurus paper at ResearchGate (not peer-reviewed)

A fourth Langobardisaurus: Saller et al. 2013

Not sure how I missed this five years ago,
knowing my fondness and fascination with the Tritosauria. I learned about the following paper while reading Franco Saller’s doctoral thesis on Macrocnemus and its allies. (More on this later).

Saller et al. 2013
describe a fourth Langobardisaurus (Late Triassic, Norian; Figs. 1-2; P10121), wrongly described as a protorosaurian reptile. Langobardisaurs are tritosaur lepidosaurs in the large reptile tree (LRT, 1326) which tests and includes more taxa.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2. Note the sprawling lepidosaur femora. The pectoral girdle is shown in situ. Colors match reconstruction in figure 2.

Saller et al. report: “Reappraisal of all the specimens assigned to the genus Langobardisaurus reveals no significant differences between L. pandolfii and L. tonelloi, allowing to consider the latter as a junior synonym of the former.” I haven’t tested more than one Langobardisaurus in phylogenetic analysis…yet… but I will as I wonder about the validity of this Saller et al. conclusion, which does not appear to be validated given the variety present in these three reconstructions (Fig. 2).

Addendum December 4, 2018:
I just added three new Langobardisaurus specimens to the LRT. The P10121 specimen is basal, nesting between the small Macrocnemus BES SC111 specimen and Cosesaurus, but definitely in the lineage of derived langobardisaurs and having a few derived traits itself. The Langobardisaurus holotype MCSNB 2883 splits next. The MFSN 1921 specimen nests with the MCSNB 4860 specimen (Fig. 2). 

Figure 1. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Figure 2. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Historically,
Langobardisaurus was the first specimen in which tracing elements in a photo using a mouse on a computer monitor revealed more than was observed firsthand and published in the original paper. Specifically the overlooked skull and cervicals were traced hiding beneath the torso (Fig. 3).

Langobardisaurus pandolfi

Figure 3. Langobardisaurus pandolfi referred specimen, MCSNB 4860.

The Langobardisaurus pectoral girdle
is transitional between the walking morphology of HuehuecuetzpalliMacrocnemus and flapping morphology of Cosesaurus (Fig. 4), as we learned earlier here. The P10121 specimen exposes the wide sternum, strap-like scapulae, disc-like coracoids and cruciform interclavicle first seen in L. tonneloi (Figs. 4, 5).

Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Figure 4. Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Bipedal Langobardisaurus
Like aquatic Tanystropheus and flapping Cosesaurus, Langobardisaurus was often bipedal, using its long neck as a survival advantage. Like Cosesaurus, this specimen of Langobardisaurus has prepubes (Fig. 6), which add femoral muscle anchors to the pelvis.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia. Also note the feathery soft tissue in orange and lime yellow. For those interested in the DGS method, this is how it works.

Figure 7. Fourth Langobardisaurus reconstruction.

Figure 7. Fourth Langobardisaurus P10121 reconstruction based on DGS tracings in figure 1.

References
Muscio G 1997. Preliminary note on a specimen of Prolacertiformes (Reptilia) from the Norian (Late Triassic) of Preone (Udine, north-eastern Italy). Gortania – Atti del Museo Friulano di Storia Naturale 18:33-40.
Renesto S 1994. A new prolacertiform reptile from the Late Triassic of Northern Italy. Rivista di Paleontologia e Stratigrafia 100(2): 285-306.
Renesto S and Dalla Vecchia FM 2000. The unusual dentition and feeding habits of the Prolacertiform reptile Langobardisaurus (Late Triassic, Northern Italy). Journal of Vertebrate Paleontology 20: 3. 622-627.
Renesto S and Dalla Vecchia FM 2007. A revision of Langobardisaurus rossii Bizzarini and Muscio, 1995 from the Late Triassic of Friuli (Italy)*. Rivista di Paleontologia e Stratigrafia 113(2): 191-201. online pdf
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.
Saller F, Renesto S and Dalla Vecchia FM 2013. First record of Langobardisaurus (Diapsida, Protorosauria) from the Norian (Late Triassic) of Austria, and a revision of the genus. Neues Jahrbuch für Geologie und Paläontologie 268(1):83–95.
Wild R 1980. Tanystropheus (Reptilia: Squamata) and its importance for stratigraphy. Mémoires de la Société Géologique de France, N.S. 139:201–206.

uninisubria/Langobardisaurus
wiki/Langobardisaurus
http://reptileevolution.com/langobardisaurus.htm

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

Paul Ellenberger RIP

I just learned of the death in 2016
of Paul Ellenberger, a French paleontologist from Montpellier, who reached the age of 97 and wrote about Cosesaurus and several ichnotaxa, as we learned earlier here, here and here.

Ellenberger was kind enough
to host me, a stranger, for a day and a night, following my visit to Cosesaurus in Barcelona in the mid 1990s. We talked about it. I tried to convince him that he should be pleased to be the discoverer of the ‘mother of all pterosaurs‘, but he continued to insist it was a pre-bird. His discovery was published in 1974, but his conclusions were invalidated by several others, including Sanz and López-Martinez 1984, who considered Cosesaurus a juvenile Macrocnemus (which is close, but no cigar) and a lepidosaur (which was later confirmed by the large reptile tree.)

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 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. This is a sister to the ancestor of pterosaurs. Note the antorbital fenestra without a fossa, convergent with proterosuchids.

Sad news about Cosesaurus
The authors of the Wikipedia Cosesaurus page have erased nearly all (but see below) data and references to Peters 2000a, the first paper that included Cosesaurus and related taxa added to several previously phylogenetic analyses that included archosaurs and pterosaurs. That study found pterosaurs nested with Cosesaurus and kin, not archosaurs in every analysis. The removal of this citation from the Wiki page is equivalent to sweeping data under the rug. Peters 2000a was a peer-reviewed publication in a respected academic journal.

If you’re looking for the ancestors of pterosaurs,
Cosesaurus is where you look. You can test the Peters 2000 hypothesis yourself with your own observations and phylogenetic analysis.

Perhaps an oversight,
the Wikipedia authors failed to delete the image of Cosesaurus that I provided several years ago with this caption:

“Here is the fossil known as Cosesaurus aviceps, the sole specimen of this genus. Although lizard-like in appearance, this Middle Triassic fenestrasaur/lizard had certain traits that place it on the lineage of Sharovipteryx, Longisquama and pterosaurs. Among these traits are: an elongated narial opening, an antorbital fenestra, a very large orbit, a spike-like quadratojugal, a strap-like scapula, a stem-like coracoid, an enlarged sternum displaced anteriorly to align with transverse clavicles, a pteroid, an elongated anterior process of the ilium, a sacrum consisting of four vertebrae, a prepubis, a simple hinge ankle joint without fusion of the astragalus and calcaneum, a calcaneum without a “heel” and an elongated pedal digit 5, plus soft tissue membranes arising from the trailing edges of the limbs and the dorsal margin of the spine and skull. No digits were vestigial, but manual digit V was reduced.”

As you might remember
earlier the authors of the Wikipedia page on pterosaurs lied with regard to my access to fossils. This line of thinking follows in lockstep Darren Naish’s bogus propaganda regarding the ReptileEvolution.com website, reviewed here. Naish’s blog and other efforts has gained followers and that’s not good for science. I hate to say it, but he’s going to come out as the leader of his suppressive minions when historians look back at this decade, unless he comes out and redeems himself soon. In private correspondence, I recently invited Naish to comment on the several recent papers that confirmed nestings first discovered in the LRT, but he dismissed that invitation. So we’ll have to fight this suppression of data a while longer.

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

Macrocnemus skull in DGS

This started with
a fuzzy photo of a  complete fossil Macrocnemus specimen, PMR T2472 (Fig 1).

Figure 7. Skull of the T2472 specimen attributed to Macrocnemus. Epipterygoids are displaced to the orbit and anterior orbit region.

Figure 1. Skull of the T2472 specimen attributed to Macrocnemus with higher resolution. Earlier mistakes (below) are corrected here.  Epipterygoids are displaced to the orbit and anterior orbit region.

Figure 1. GIF animation of PMR T2472, a large Macrocnemus in situ and reconstructed from a fuzzy photo.

Figure 1. GIF animation of PMR T2472, a large Macrocnemus in situ and reconstructed from a fuzzy photo.

Many specimens attributed to Macrocnemus
are known, each one a little different phylogenetically. Reports of a ‘juvenile’ Macrocnemus refer to the phylogenetically basalmost and smallest of the known specimens, the one closest to its outgroup taxon, the tritosaur lepidosaur, Huehuecuetzpalli.

It’s good to remind yourself
before reading the reference titles, that Macrocnemus and kin are not protorosaurs (= prolacertiforms), nor are they archosauriforms. Even I made the same mistake (Peters 2000b) in my more naive days before the LRT recovered Macrocnemus and kin as tritosaur lepidosaurs in Peters 2007.

From this rather ordinary taxon arises 
such diverse and exotic taxa as Dinocephalosaurus, Sharovipteryx, a variety of Tanystropheus, several Langobardisaurus, Longisquama and pterosaurs. Peters 2007 reported, “The basal lizard, Huehuecuetzpalli is the most primitive taxon in this newly revealed third squamate clade between Iguania and Scleroglossa. Two branches arise from it. Jesairosaurus is basal to the Drepanosauridae. Three distinct specimens of Macrocnemus give rise to the Tanystropheidae,the Langobardisaurinae and to the Fenestrasauria respectively.” Jesairosaurus and Drepanosauridae are now basal lepidosauriformes.

References
Li C, Zhao L-J and Wang L-T 2007A new species of Macrocnemus (Reptilia: Protorosauria) from the Middle Triassic of southwestern China and its palaeogeographical implication. Science in China D, Earth Sciences 50(11)1601-1605.
Li C, Wu X-C, Zhao L-J, Nesbitt SJ, Stocker MR, Wang L-T 2016. A new armored archosauriform (Diapsida: Archosauromorpha) from the marine Middle Triassic of China, with implications for the diverse life styles of archosauriforms prior to the diversification of Archosauria. The Science of Nature 103: 95. doi:10.1007/s00114-016-1418-4
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
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 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peyer B 1937. Die Triasfauna der Tessiner Kalkalpen XII. Macrocnemus bassanii Nopcsa. Abhandlung der Schweizerische Palaontologische Geologischen Gesellschaft pp. 1-140.
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.
Romer AS 1970. Unorthodoxies in Reptilian Phylogeny. Evolution 25:103-112.

wiki/Macrocnemus

 

More data on the scaly fenestrasaur, Kyrgyzsaurus

Updated March 3, 2016 with a reconstruction from the tracings.

An earlier nesting
in the large reptile tree placed the Late Triassic reptile Kyrgyzsaurus not with drepanosaurs, but with fenestrasaurs, between Cosesaurus and higher taxa, all bipeds or near bipeds. The parallelogram-shaped cervicals indicate the skull was held higher than the shoulders, as in pterosaurs, Longisquama and Cosesaurus. 

Figure 1. New data on Kyrgyzsaurus provides the first evidence for forelimbs.

Figure 1. New data on Kyrgyzsaurus provides the first evidence for forelimbs. This is the first time I’ve seen the bones in color. Note: Spindler thought the forelimb was tiny, but did not trace left forelimb elements, only the elbow visible over the dorsals. This is an example of DGS. Higher resolution would enable further details to be traced.

New photos
(Fig. 1) of what appear to have come from an abstract posters provided online by Spindler et al. 2014 reveal more data for Kyrgyzsaurus, including a complete pectoral girdle and tiny forelimb with laterally folding digit 4 (as in pterosaurs), adding to the possibility that long hind limbs probably gave this taxon a bipedal configuration as well (based on phylogenetic bracketing). Longisquama and Sharovipteryx were sisters and contemporaries that likewise had short arms.

Figure 2. Updated figure of Kyrgyzsaurus.  Note the tiny forelimbs and large hyoid, as in Sharovipteryx.

Figure 2. Updated figure of Kyrgyzsaurus. Note the tiny forelimbs and large hyoid, as in Sharovipteryx.

The abstract discusses
coloration in the scales, not unexpected as exquisitely preserved Late Triassic insects likewise preserve coloration in this formation.

From the poster
“Dorsally the scales are generally smaller, but conspicuous craniocaudal rows of large oval to rectangular scales occur within the meshwork of smaller scales. The reddishly preserved skin colouration follows no simple pattern: There is a larger color patch along the posterior margin of the skull, the ventral neck and anterior trunk display scales with tiny colour spots, and the dorsal rows of larger scales are sometimes marked by thin aligned stripes.”

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

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

Unfortunately Spindler et al.
were unable to decipher their own precise tracings and so overlooked the forelimb of Kyrgyzsaurus. In this case it might have been important for them to understand where this specimen nested in the reptile family tree (published here in 2012). They considered it merely as ‘a reptile’ with tiny forelimbs with very, very small fingers, evidently imagined. They did not even call it Kyrgyzsaurus, or make reference to the original paper (Alfanov and Kurochkin 2011), even though the specimen was named three years earlier. It is clear that Spindler et al. did not trace fingers, but guessed at their presence. They labeled the ‘pectoral girdle’ with a vague arrow, but not the individual elements. Maybe none of this matters, as their study focused on skin coloration.

DGS
(digital graphic segregation), a reconstruction, and a phylogenetic analysis once again pulled data out of an online photo that was overlooked by first hand observers.

References
Alifanov VR and Kurochkin EN 2011. Kyrgyzsaurus bukhanchenkoi gen. et sp. nov., a new reptile from the triassic of southwestern Kyrgyzstan. Paleontological Journal 45(6): 639–647. doi:10.1134/S0031030111060025.
Spindler F, Buchwitz M, Fischer J and Voigt S 2014. Preservation of tetrapod skin in the Triassic Madygen Formation. Conference: 82. Jahrestagung der Paläontologischen Gesellschaft, At Vienna (Austria), Volume: Beiträge zur Paläontologie – Program and Abstracts 32: pp. 76–77.

wiki/Kyrgyzsaurus