SVP abstracts 22: Weigeltisaurus reexamined

Pritchard, Sues, Reisz and Scott 2020
promise to bring us a look at the ‘osteology and phylogenetic affinities of the early gliding reptile Weigeltisaurus jaekeli” (Fig. 1).

Unfortunately,
no phylogenetic analysis, or any hint thereof, is to be found in the abstract.

We looked at Weigeltisaurus earlier
here when the skull (Fig. 1) was described by Bulanov and Sennikov 2015.

Figure 1. Weigeltisaurus skull reconstructed by Bulanov and Sennikov (gray scale), and using DGS techniques (color). They did not attempt to trace the occiput, nor did they understand that the posterior crest is the supratemporal, displaced in situ and that the main portion is a very large squamosal that sweeps up. This skull is nearly identical to that of sister taxa, with the exception of the extended posterior elements, probably for secondary sexual selection. The same cannot be said of the Bulanov and Sennikov reconstruction which is, unfortunately, unique as is.

Weigeltisaurus is a relative of Coelurosauravus 
(Fig. 2) and other pseudo-rib gliders. The ribs are dermal in nature, extending from the tips of the dorsal and lumbar ribs, whether few or many.

Figure 2. Click to enlarge. The Triassic kuehneosaur gliders and their non-gliding precursors. Note the icarosaurs are not rib gliders. Their actual ribs are fused to mimic transverse processes as demonstrated around the neck and anterior torso.

From the Pritchard et al. 2020 abstract:
“Weigeltisauridae is a clade of small-bodied Permian diapsids that represent the oldest known vertebrates with skeletal features for gliding. It is characterized by a cranium with a posterior bony casque, prominent horns on the temporal arches, and a series of elongate bony spars projecting from the ventrolateral surface on both sides of the trunk. Definitive specimens are known from upper Permian of Germany, Russia, and Madagascar, but the quality of their preservation previously limited understanding of the skeletal structure and phylogenetic affinities of these reptiles.”

All you have to do is add taxa (= minimize taxon exclusion) and let the software determine where these Permian pseudo-rib gliding lepidosauriforms nest. In the large reptile tree (LRT, 1752+ taxa; subset Fig. 3) these arboreal gliders nest at the base of the lepidosauriformes. (The Diapsida is now limited to just archosauromorphs with a diapsid-skull morphology, by convergence with lepidosauriformes). Only here, in the LRT, among all prior pertinent cladograms, is the clade of pseudo-rib gliders surrounded by arboreal taxa with weigeltosaurs nesting with kuehneosaurs. Usually they nest apart and too often close to marine taxa.

Figure 2. Derived lepidosauriformes. The clade Pseudoribia includes the pseudo-rib gliders

The Pritchard, Sues, Reisz and Scott abstract continues:
“Here, we present a revised account based on a nearly complete skeleton of Weigeltisaurus jaekeli from the Kupferschiefer of central Germany and a revised phylogenetic analysis of early Diapsida and early Sauria.”

That analysis must have been part of the oral presentation. There is no hint of it here. Sauria is an invalid clade. Diaspsida is restricted to the Archosauromorpha in the LRT.

“The specimen preserves all elements of the skeleton, save for the braincase, palate, some dorsal vertebrae, the carpus, and the tarsus. The well-preserved teeth in the maxilla are not conical but leaf-shaped, resembling those in the middle portion of the maxillae of the Russian weigeltisaurid Rautiania. The parietals bear rows of dorsolaterally oriented horns similar to those on the squamosals. The quadrate is a dorsoventrally short element with a tapering dorsal margin that lacks a cephalic condyle. The squamosal appears to cover the quadrate both laterally and posterodorsally. The manual and pedal phalanges are elongate and slender, similar to those of extant arboreal squamates. The unguals have very prominent flexor tubercles. A patagium was supported by elongate, slender bony rods. They are situated superficial to the preserved dorsal ribs and gastralia, corroborating the hypothesis that these structures represent dermal ossifications independent of and greater in number than the bones of the dorsal axial skeleton.”

Excellent description. But that was provided earlier (Bulanov and Sennikov 2015).

Phylogenetic conclusions? 
I guess we’ll have to wait for the paper.

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References
Bulanov VV and Sennikov AG 2015. Substantiation of validity of the Late Permian genus Weigeltisaurus Kuhn, 1939 (Reptilia, Weigeltisauridae) Paleontological Journal 49 (10):1101–1111.
Pritchard A, Sues HD, Reisz R and Scott D 2020. Osteology and phylogenetic affinities of the early gliding reptile Weigeltisaurus jaekeli. SVP abstracts.

https://pterosaurheresies.wordpress.com/2011/09/26/icarosaurus-kuehneosaurus-and-the-so-called-rib-gliders/

https://pterosaurheresies.wordpress.com/2015/12/17/weigeltisaurus-skull-reconstructions/

Prior citations
Colbert, Edwin H. (1966). A gliding reptile from the Triassic of New Jersey. American Museum Novitates 2246: 1–23. online pdf
Evans SE 1982. Gliding reptiles of the Late Permian. Zoological Journal of the Linnean Society, 76:97–123.
Evans SE and Haubold H 1987. A review of the Upper Permian genera  Coelurosauravus, Weigeltisaurus and Gracilisaurus (Reptilia: Diapsida). Zool J Linn Soc, 90:275–303.
Fraser NC, Olsen PE, Dooley AC Jr and Ryan TR 2007. A new gliding tetrapod (Diapsida: ?Archosauromorpha) from the Upper Triassic (Carnian) of Virginia. Journal of Vertebrate Paleontology 27 (2): 261–265. doi:10.1671/0272-4634(2007)27[261:ANGTDA]2.0.CO;2.
Frey E, Sues H-D and Munk W 1997. Gliding Mechanism in the Late Permian Reptile Coelurosauravus. Science Vol. 275. no. 5305, pp. 1450 – 1452
DOI: 10.1126/science.275.5305.1450
Li P-P, Gao K-Q, Hou L-H and Xu X. 2007. A gliding lizard from the Early Cretaceous of China. PNAS 104(13): 5507-5509. doi: 10.1073/pnas.0609552104 online pdf
Modesto SP and Reisz RR 2003. An enigmatic new diapsid reptile from the Upper Permian of Eastern Europe. Journal of Vertebrate Paleontology 22 (4): 851-855.
Modesto SP and Reisz RR 2011. The neodiapsid Lanthanolania ivakhnenkoi from the Middle Permian of Russia, and the initial diversification of diapsid reptiles. SVPCA abstract.
Robinson PL 1962. Gliding lizards from the Upper Keuper of Great Britain. Proceedings of the Geological Society London 1601:137–146.
Stein K, Palmer C, Gill PG and Benton MJ 2008. The aerodynamics of the British Late Triassic Kuehneosauridae. Palaeontology, 51(4): 967-981. DOI: 10.1111/j.1475-4983.2008.00783.x
Piveteau J 1926. Paleontologie de Madagascar, XIII. Amphibiens et reptiles permiens: Annales de Paleontologie, v. 15, p. 53-128.

The rest of Lonchodraco probably looks like this large unnamed ornithocheird

Only the deep toothy jaw tips,
of the pterosaur Lonchodraco giganteus (Hooley 1914; Rodrigues & Kellner 2013; NHMUK PV 39412; originally Pterodactylus giganteus Bowerbank 1846; Fig. 1) are known. Ever wonder what the rest of this pterosaur looked like?

Well,
the 174-year wait is over.

Figure 1. Lonchodraco jaw tips. Colors added here. For the rest of this genus, see figure 2. The nasal (pink) is laminated between the premaxilla (yellow) and maxilla (green). The jugal (blue) also makes an appearance.

What little is known of Lonchodectes turns out to look like
the (so far) unnamed large ornithocheirid, SMNK PAL 1136 (Fig. 2) one of the largest of all flying pterosaurs. The very few parts they have in common are virtually identical, except for size (note the scale bars provided).

Figure 2. The unnamed giant ornithocheirid, SMNK PAL 1136 has a rostrum quite similar to that of Lonchodectes. With such giant wings, soaring over wave tops would have been ideal, dipping occasionally to feed without getting wet.

As one of the largest flying pterosaurs,
SMNK PAL 1136 (Figs. 2, 3) presents no vestigial terminal wing phalanges. No hyper-elongated neck cervicals are present. This pterosaur was built to soar like a big pelican.

Sorry, giant azhdarchids lovers 
(Fig. 3). Those were not volant, as we learned earlier here. They grew to be so big AFTER they became flightless, like flightless birds do. Giant azhdarchids DO have vestigial wing phalanges and a hyper-elongated neck.

Figure 3. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Earlier workers 
did not match Lonchodraco to the SMNK PAL 1136 specimen. Earlier workers did not name the SMNK specimen. Perhaps someone is working on that specimen at present and other workers are giving him/her the honor/duty of naming it.

Wonder if
the Lonchodraco name will stick to the SMNK specimen?

Recently, Martill et al. 2020 took a close look
at the foramina in the jaw tips of Lonchodraco and thought they indicated enhanced sensitivity of the rostrum tip, which implied tactile feeding. With such giant wings, soaring over wave tops would have been likely, dipping occasionally to feed without getting the wings wet.

Odd that the top workers at the top universities
have decided to spend their time examining tiny pits on a broken 174-year-old pterosaur snout while ignoring the origin of pterosaurs… while ignoring many dozen complete pterosaurs that should be in phylogenetic analysis… while ignoring the lepidosaurs that gave rise to the ancestors of pterosaurs. Unfortunately, that’s the world academics live in today. They keep trying to not upset the lectures and textbooks from which they make their living. Apparently if academics focus on the details they won’t have to worry about the big picture. No one will ever know the difference if no one points out the elephant in the room.

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References
Averianov AO 2020. Taxonomy of the Lonchodectidae (Pterosauria, Pterodactyloidea). Proceedings of the Zoological Institute RAS. 324 (1): 41–55. doi:10.31610/trudyzin/2020.324.1.41
Bowerbank JS 1846. On a new species of pterodactyl found in the Upper Chalk of Kent (Pterodactylus giganteus). Quarterly Journal of the Geological Society of London. 2: 7–9.
Bowerbank JS 1848. Microscopical observations on the structure of the bones of Pterodactylus giganteus and other fossil animals”. Quarterly Journal of the Geological Society. 4: 2–10.
Martill DM, Smith RE, Longrich N and Brown J 2020. Evidence for tactile feeding in pterosaurs: a sensitive tip to the beak of Lonchodraco giganteus (Pterosauria, Lonchodectidae) from the Upper Cretaceous of southern England. Cretaceous Research
Available online 3 September 2020, 104637 Cretaceous Research https://doi.org/10.1016/j.cretres.2020.104637
Rodrigues T and Kellner A 2013. Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England. ZooKeys. 308: 1–112. doi:10.3897/zookeys.308.5559

wiki/Lonchodraco

The flying fish (Exocoetus) enters the LRT alongside the rudder fish

Updated February 4, 2021
with the addition of taxa, Exocoetus nests with Seriola sonata, the rudder fish.

Nesting flying fish (Exocoetus) with swordfish (Xiphias)
(Figs. 1–3) in the large reptile tree (LRT, 1542 taxa; subset Fig. 4) seems like an odd pairing. Even so, no tested taxon is closer to swordfish than flying fish...

Figure 1. Flying fish (Exocoetus) skull.

 

Figure 2. Flying fish (Exocoetus volitans) line drawing.

Exocoetus volitans (Linneaus 1758; up to 30m ) is the extant blue flyingfish, here related to the swordfish, Xiphias. Exocoetus travels in schools or schoals. Sometimes they exit the water to avoid predators. Juveniles have a relatively shorter torso. Hatchlings are slow-moving and tiny. Note the antorbital fenestra and large lacrimal, as in Xiphias. Distinctly flying fish have a jaw joint directly below the orbit. The coracoid is larger than the scapula, raising the pectorl fins.

Seriola zonata (Valenciennes 1833; commonly 50cm, up to 75cm) is the extant banded rudderfish. Large individuals (over 10 inches) have no abdominal bands,  but a raccoon-stripe on the eye and an iridescent gold stripe on the side are present. Adults are usually called amberjacks. Striped juveniles are usually called pilotfish. This generic fish is basal to a wide variety including flying fish, puffers, frogfish, anglers and mudskippers.

If I missed a citation that predates this one
that supports this hypothesis of interrelationships, please send me the citation. It does not appear to be matched by genomic (gene/molecule) studies.

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References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Valenciennes A in Cuvier G and Valenciennes A 1833. Histoire naturelle des poissons. Tome neuvième. Suite du livre neuvième. Des Scombéroïdes. 9: i-xxix + 3 pp. + 1-512. Pls. 246-279.

wiki/Exocoetus_volitans
wiki/Seriola
wiki/Amberjack

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 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. 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.

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.

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 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).

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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

“Kinematics of wings from Caudipteryx to modern birds”: Talori et al. 2018

A new paper without peer-review by Talori, Zhao and O’Connor 2018
seeks to “better quantify the parameters that drove the evolution of flight from non-volant winged dinosaurs to modern birds.”

Unfortunately
they employ Caudipteryx, an oviraptorosaur. They correctly state, “Currently it is nearly universally accepted that Aves belongs to the derived clade of theropod dinosaurs, the Maniraptora.” They incorrectly state, “The oviraptorosaur Caudipteryx is a member of this clade and the basal-most  maniraptoran with pennaceous feathers.” In the large reptile tree (LRT, 1269 taxa) oviraptorosaurs nest with therizinosaurus, and more distantly ornithomimosaurs. This clade is separated from bird ancestor troodontids by the Ornitholestes/Microraptor clade.

Figure 1. Caudipterys is in the peach-colored clade, far from the lineage of birds.

The Talori team
mathematically modeled Caudipteryx with three hypothetical wing sizes, but failed to provide evidence that the Caudipteryx wing was capable of flapping. In all flapping tetrapods the elongation of the coracoid  (or in bats of the clavicle) signals the onset of flapping… and Caudipteryx does not have an elongate coracoid. Rather, it remains a disc.

So, no matter the math, or the accuracy of the mechanical model,
the phylogeny is not valid and the assumption of flapping is inappropriate. It would have been better if they had chosen a troodontid and several Solnhofen birds to test.

Tossing those issues aside,
the Talori team did an excellent job of setting their mechanical model (which could be a troodontid) in a wind tunnel, extracting data from three different wing shapes and presenting their findings. Feathers would have been more flexible than their mold manufactured wings, but the effort is laudable.

References
Zhao J-S, Talori YS, O’Connor J-M 2018. Kinematics of wings from Caudipteryx to modern birds. [not peer-reviewed] bioRXiv
https://www.biorxiv.org/content/early/2018/08/16/393686

http://reptileevolution.com/reptile-tree.htm

Where would drepanosaurs nest, if Jesairosaurus was not known?

We’re getting back
to an older series today as we ‘play’ with the large reptile tree (1262 taxa, LRT) by cherry-deleting taxa.

Drepanosauromorpha are so distinct from other reptiles
that experts have been hard at work trying to figure out what they are—without success or consensus. There are so many competing ideas (which means none are convincing) that I’m going to refer you to the Wikipedia page on Drepanosauridae that lists and discusses them all with citations. The latest work (Pritchard and Nesbitt 2017) recovered a very basal diapsid nesting, but they did not realize that lepidosaur ‘diapsids’ were not related to archosaur ‘diapsids’, due to taxon exclusion at the genesis of reptiles.

Figure 3. Drepanosaurs and their ancestor sisters, Jesairosaurus and Palaegama to scale.

Unfortunately,
all prior workers omitted or overlooked the widely tested closest relatives, Jesairosaurus (Jalil 1997, Fig. 1) followed by the basal lepidosauriformes, Tridentinosaurus, Lanthanolania, Sophineta and Palaegama (Fig. 1) in the LRT, which tests all prior sister candidates Megachirella (Fig. 2), at the base of the Rhynchocephalia (Fig. 3), is also closely related in the LRT. So, once again, taxon exclusion is the problem in all prior studies. Jesairosaurus was documented as the last common ancestor of drepanosauromorpha here in October 2012. This is not one of those “obvious as soon as you realize it” nestings. You really do need the wide gamut testing of the LRT to eliminate all other candidates.

FIgure 2. Megachirella (Renesto and Posenato 2003) is a sister to the BSRUG diapsid.

So let’s play the game of taxon exclusion…

If Jesairosaurus and all Archosauromorpha are deleted,
the remaining drepanosauromorphs do not shift to another node within the Lepidosauromorpha.

If Jesairosaurus and Hypuronector and all Archosauromorpha are deleted,
the remaining drepanosauromorphs do not shift to another node, and nest with basalmost Sphenodontia, like the BSRUG 29950-12 specimen related to Megachirella and Pleurosaurus.

If Lepidosauromorpha and Diapsida are deleted,
Jesairosaurus and the drepanosauromorphs nest with the herbivorous synapsids, Suminia and Dicynodon.

If Lepidosauromorpha and Diapsida are deleted,
Megalancosaurus alone nests between the herbivorous synapsids Venjukovia + Tiarajudens and Suminia + Dicynodon.

Figure 3. Subset of the LRT focusing on basal lepidosauriformes and Jesairosaurus at the base of the Jesairosauria. Several new clades are named here.

If only Diapsida is tested,
Jesairosaurus and the remaining drepanosauromorphs nest as a clade between the sauropterygians and mesosaurs + thalattosaurs + ichthyosaurs.

If only Diapsida is tested,
Megalancosaurus alone nests between the sauropterygians and mesosaurs + thalattosaurs + ichthyosaurs.

Nomenclature and some suggestions:

1. Jesairosauria — Jesairosaurus, Megachirella, their last common ancestor all descendants. More taxa reveal this phylogenetic pattern that has, so far, escaped the notice of professional paleontologists.
2. Rhynchocephalia — Gephyrosaurus, Megachirella, their last common ancestor all descendants.
3. Sphenodontia —  Sphenodon, Ankylosphenodon, their last common ancestor all descendants.
4. Transphenodontia — Trilophosoaurus, Mesosuchus, their last common ancestor all descendants. These taxa bridge the gap between sphenodonts and rhynchosaurs and include the latter. More taxa reveal this phylogenetic pattern that has, so far, escaped the notice of professional paleontologists.
5. Rhynchosauria — Rhynchosaurus, Hyperodapedon, their last common ancestor all descendants.
6. Pseudoribia — Coelurosauravus, Icarosaurus, their last common ancestor all descendants. These so-called ‘rib-gliders’ actually use elongate dermal ossifications to extend their gliding membranes. More taxa and a closer examination of Icarosaurus and kin reveal this clade that has, so far, escaped the notice of professional paleontologists.

The related taxa shown
in figure 3 as a subset of the large reptile tree come together by way of taxon inclusion. Prior workers missed these relationships by excluding taxa. Rhynchosaurs were once considered Rhynchocephalians, but recently that has not been accepted based on the invalidated hypothesis that rhynchosaurs were archosauriformes.

Invalidated or modified nomenclature:

1. Allokotosauria — While protorosaurs, including Pamelaria, are basal members of the new Archosauromorpha, Trilophosaurus and Azendohsaurus are members of the new Lepidosauromorpha.
2. Diapsida — The LRT documents two unrelated clades evolving diapsid skull architecture. In the LRT only archosauromorph diapsids are considered Diapsida. More taxa reveal this pattern that has, so far, escaped the notice of professional paleontologists.

I hope readers enjoy and learn from these daily blogs.
If you disagree with any of the results, I encourage you to run your own tests with similar taxon lists, then let us all know if you confirm or refute the LRT results. Don’t be like those who just hurl adjectives at the work done here. Keep up your professional demeanor and attitude and be prepared to accept new discoveries if they cannot be refuted. The strength of the LRT is that is covers all available candidates and minimizes taxon exclusion problems that plague smaller prior studies.

References
Jalil N-E 1997. A new prolacertiform diapsid from the Triassic of North Africa and the interrelationships of the Prolacertiformes. Journal of Vertebrate Paleontology 17(3), 506-525.
Pritchard AC and Nesbitt SJ 2017. A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida. Royal Society Open Science DOI: 10.1098/rsos.170499

wiki/Jesairosaurus
wiki/Drepanosaur
wiki/Allokotosauria

Where does the frigate bird nest?

For a blog focused on pterosaurs
it sure took a long time to take a look at the extant frigate bird (Figs. 1-3; genus: Fregata), a modern analog for many of the sea-faring clades of pterosaurs in terms of wing shape (long span, short chord) and gliding ability (see below).

FIgure 1. Fregata in flight. Note the narrow-chord wing membrane, as in all pterosaurs.

Between pelicans and cormorants 
In the large reptile tree (LRT, 1227 taxa) the frigate bird nests between the clade Pelecanus + Balaeniceps (the shoebill) and Phalacrocorax (the cormorant). The shoebill has the longest legs in the clade, so it is the most primitive member. Most studies, including the LRT and DNA analyses, associate frigate birds with pelicans, skuas and petrels, but some link frigate birds with a larger list including herons, ibises, spoonbills, hamerkops, penguins, loons, gannets, and cormorants. Why can’t DNA be more specific? That’s a wide gamut of taxa. The LRT is specific and fully resolved.

FIgure 2. Fregata skull with a closeup of the tiny jugal.

Interesting that frigate birds don’t like to get wet
while their sisters, cormorants dive for food, but then have to stand with wings dripping while drying out. Distinct from ducks, cormorant feathers don’t shed water with an oily coat.

Figure 3. Skeleton of Fregata, the frigate bird. Note the long bill, long neck and long antebrachium, perhaps the closest living analog to Cretaceous ornithocheirid and pteranodontid pterosaurs (Fig. 5). Consider this a shoebill stork and/or pelican with a slender bill and very short legs and you will be close to its phylogenetic grade.

Fregata magnificens (Lacépède, 1799; up to 56 cm long) inflates its throat sac with air, like a balloon, to display its bright red color (distinct from the pelican throat sac, which fills with water and prey). According to Wikipedia, “frigatebirds spend most of the day in flight hunting for food, and roost on trees or cliffs at night. The duration of parental care is among the longest of any bird species; frigatebirds are only able to breed every other year. Fossils date back to the Eocene, 50 mya.” 

Figure 4. Cearadactylus, Anhanguera and Pteranodon compared. The inset compares the humerus of Anhanguera and Pteranodon. Compare proportions to the skeleton of Fregata. Look at those long wing tips, completely different from flightless pterosaurs, including large to giant azhdarchids. Most workers consider these taxa to be closely related, but the LRT does not confirm that.

Tested frigate birds
(Huey and Deutsch 2016) stayed aloft for two months without ever touching the ground riding cumulus thermals up to 6500 feet above sea level. 

Like ornithocheirid and pteranodontid pterosaurs
the torso is small and the wing has a narrow chord and a wide span in Fregata. This is also like modern man-made gliders, and unlike the proportions found in large to giant azhdarchids, which could not fly at all, contra traditional thinking, based on their relatively short distal wing finger phalanges (like those of small flightless pterosaurs).

References
Huey RB and Deutsch C 2016. How frigate birds soar around the doldrums. Science 353 (6294):26–27.
Lacépède BGÉ de 1799. Discours d’ouverture et de clôture du cours d’histoire naturelle : donné dans le Muséum national d’Histoire naturelle, l’an VII de la République, et tableaux méthodiques des mammifères et des oiseaux, Paris.

wiki/Frigatebird

Do gliding lizards (genus: Draco) actually grab their extended ribs?

Figure 1. Extant Draco flying with hands beneath the leading edge of the membrane, not anterior to it. Images from Dehling 2016.

Gliding lizards
of the genus Draco (Figs. 1, 2) come in a wide variety of species. Similar but extinct gliding basal lepidosauriformes, like Icarosaurus (Fig. 2), form a clade that arose in the Late Permian and continued to the Early Cretaceous.

Figure 2. Two Draco species fully extending their rib membranes without the use of the hands.

A recent paper
(Dehling 2016) reported, “the patagium is deliberately grasped and controlled by the forelimbs while airborne.” Evidently this ‘membrane-grab’ behavior has not been noted before. I wondered if the rib skin is indeed grasped, or does the forelimb merely fold back against the leading edge of the patagium in a streamlined fashion? Photographs of climbing Draco specimens (Fig. 2) show that the patagium  can fully extend without the aid of the forelimbs to stretch them further forward.

Figure 3. Icarosaurus. Note the tiny ribs near the shoulders. The bases for the strut-like dermal bones are the ribs themselves flattened and transformed by fusion to act like transverse processes, which sister taxa do not have. Note the length of the hands corresponds to the base of the anterior wing strut, a great place to rest the manus or grab the membrane.

A quick review of prehistoric gliding keuhneosaurs
(Fig. 3) show that the manus unguals are not quite as large and sharp as those of the pes and that the manus in gliding mode extends just beyond the shorter two anterior dermal struts so that the glider -may- have grasped the anterior struts in flight. Or may have rested the manus there. Remember, these are taxa unrelated to the extant Draco, which uses actual ribs to stretch its gliding membrane. The same holds true for the more primitive Coelurosauravus and Mecistotrachelos, which have not been traditionally recognized as basal kuehneosaurs.

* As everyone should know by now…
the so-called transverse processes in kuehneosaurs are the true ribs, only fused to the vertebrae. The ribs remain unfused to the vertebrae in the older and more primitive coelurosauravids. No sister taxa have transverse processes elongate or not.

References
Dehling M 2016. How lizards fly: A novel type of wing in animals.

A skeletal reconstruction of Volaticotherium

Revised July 27, 2018
with a new nesting for Volaticotherium closer to Eomaia.

Figure 1. Scientific American recently featured Volaticotherium on its cover. Did Volaticotherium have a patagium and bushy tail? Good question. James Gurney is the illustrator here. Note the fangs!

Volaticotherium antiquus (Meng et al. 2006; ?Middle Jurassic to ?Earliest Cretaceous, 164 mya; 3 cm skull length; IVPP V14739; Figs. 1-3) was described a few years back as a gliding mammal of uncertain affinity, based on a preserved patagium, or gliding membrane, complete with short hair and skin. Oddly, the patagium was preserved, but not the basic skin and fur, usually preserved as a halo around the skeleton.

Figure 2. Volaticotherium in situ, in X-ray, as originally traced (line drawing) and DGS traced (colors). Patagium is the large tan ovoid. The X-ray has different outlines and so may represent the counter plate. You can see some of the distortion necessary to align elements.

Unfortunately
the skin has slipped off the scattered roadkill skeletal elements like a bath towel (Fig. 2) leaving some doubt as to where it connected to the body and limbs. If a patagium, its symmetrical counterpart, if present, is not preserved and the skin itself seems to be fully stretched out, at odds with patagia of other flying and gliding animals, that tend to shrink went not in use. Interesting, perhaps, that the patagial outline roughly corresponds to what the basic skin of Volaticotherium would have to be. No such skin was mentioned in the text or is visible in the fossil as a halo or scattering of fur. Sister taxa, such as Eomaia and Didelphis (Fig. 5), do not have a bushy tail, as illustrated above (Fig.1).

Did female Volaticotherium glide
with exposed underdeveloped young attached only by jaws on nipples?  Bats leave their young at the roost while feeding, until they are hold enough to cling well and they have one pup at a time.  Colugos likewise have a single pup at a time and carry them in their nursery/gliding membranes. See image here. Wikipedia reports, “Colugos raise their young in a similar fashion to marsupials. Newborn colugos are underdeveloped and weigh only 35 g (1.2 oz).^[9] They spend the first six months of life clinging to their mother’s belly. The mother colugo curls her tail and folds her patagium into a warm, secure, quasi-pouch in order to protect and transport her young.”

Figure 3. Volaticotherium reconstructed. Here the patagium appears to be able to just drape over the head and torso, unlike the much larger membrane in Cynocephalus, the flying lemur. Shown as a biped here, that was likely only a temporary pose, like a squirrel on its haunches. Occipital bones are not shown.

There’s much more to this extraordinary mammal that is not controversial.
The molars resemble rotary saw blades, the external naris is divided by an ascending process of the premaxilla (rare among higher cynodonts and mammals), proximally the femur has no ‘neck’ and not much of a ‘head’, and the tail is extraordinarily long. Not listed by Meng et al., The mandible is not gently convex, but is sharply convex ventral to the canines, then gently concave, a shape not otherwise seen until higher primates. We also see a deeper mandible medial to sabertooth fangs in Thylacosmilus, and this may be the reason for the oddly deeper chin here.

Volaticotherium was deemed so different
from all other known mammals that it was given its own order, the Volaticotheria, nesting between basalmost mammals (Proteutherians) and Therians.

Here
in the large reptile tree, despite its many autapomorphies and convergent traits, Volaticotherium nests between the Eomaia clade and all higher marsupials. This is appropriate, given its Late Jurassic age. The two were roughly comparable in size.

The femoral head
of Volaticotherium was about as shallow as it could be and evidently not due to crushing. Generally a spherical femoral head provides strength and maneuverability. Cartilaginous or connective tissue may have substituted for bone in Volaticotherium. 

Other arboreal features
The hallux (big toe) diverged from the other metatarsals at 35º angle, flexor sesamoids and curved phalanges with small sharp claws indicate an arboreal niche for Volaticotherium. The limbs were all described as elongated, but only the forelimb appears elongated relative to the femur (Fig. 3). The distal phalanges would appear to be fully flexed, tucked beneath the proximal phalanges, but the X-ray does not reveal them. The long tail was likely used in balancing and leaping, like a lemur. The cervicals were very short, as in the basal primate, Notharctus, and in Longisquama, a lemur-like lepidosaur. The scapula was relatively small, as in Notharctus and Longisquama. The calcaneum was relatively short and flexible, enabling rotation of the foot for better grasping of tree trunks while heading in any direction.

There is another Jurassic sister taxon out there:
Argentoconodon (Gaetano and Rogier 2011; Fig. 6), known from teeth and scattered jaw fragments. Like Volaticotherium, the molar cusps are aligned as in pre-mammalian triconodonts. Unlike Volaticotherium, the medial incisor is the size of a canine, which appears suspect.

The holotype genus
for the triconodonts, Triconodon, provides evidence for the replacement of its lower fourth premolar, erupting and coming into use when at least three out of its four molars were already fully erupted, which is a mammal trait. Note the very low jaw articulation and sub canine ‘chin’, traits shared with Volaticotherium.

Perhaps this triconodont clade
evolved a simplified, more primitive-type tooth with aligned cusps. If so, it’s not alone. Toothed cetaceans, for instance, have only simple conical teeth.

Figure 6. Line art (w/o color) from Gaetano and Rougier 2011. This reconstruction of Argentoconodon is built from many small fragments and appears to have a few problems. Nevertheless, these fragments and those molars are similar enough to Volaticotherium to warrant interest.

I thank Dr. Meng
for sending me a pdf of his paper describing an important early arboreal mammal. I have an inquiry for him, still awaiting a reply, wondering if the simplified (primitive) molar structure of Volaticotherium, might be a derived reversal… an atavism.

References
Gaetano GW and Rougier GW 2011. New materials of Argentoconodon fariasorum (Mammaliaformes, Triconodontidae) from the Jurassic of Argentina and its bearing on triconodont phylogeny. Journal of Vertebrate Paleontology 31(4):829-843.
Meng J, Hu YM, Wang YQ, Wang XL and Li CK 2006. A Mesozoic gliding mammal from northeastern China. Nature 444:889-893.

wiki/Volaticotherium

Tridentinosaurus antiquus: a glider ancestor, not a protorosaur

I had never heard of this one before. 
Evidently this Early Permian reptile is famous for being fossilized between volcanic layers and for preserving more skin than bone. Using DGS I was able to tease out some of the bone (Fig. 1) and nest Tridentinosaurus not with the protorosaurs, as Leonardi (1959) proposed, but with basal lepidosauriforms. Tridentinosaurus nests in the large reptile tree as an Early Permian descendant of the late-surviving Palaegama and an ancestor to the Late Permian ‘rib’ glider, Coelurosauravus and the Late Triassic ‘rib’ glider, Icarosaurus along with other glider clade members.

Figure 1. Tridentinosaurus at 26.5 cm long is an Early Permian ancestor to Late Permian Coelurosauravus and Late Triassic Icarosaurus. Here two images taken in different light conditions were superimposed, then traced. An arboreal lifestyle is suspected here, based on the long limbs and toes.

Tridentinosaurus antiquus (Early Permian, Dal Piaz 1932, Leonardi 1959, 26.5cm long; Museum of Paleontology of the University of Padua 26567). Ronchi et al. described the specimen as “a beautiful but biochronologically useless specimen of which only the out−line of the soft tissues is well preserved.” The volcanic sediments in Sardinia occur in Cisuralian / Sakmarian deposits 291 million years old.

Although known for more than 50 years, 
and with quite a story to tell, this genus was not famous enough to merit its own Wikipedia page when I wrote this. Based on phylogenetic bracketing, the tail may have been twice as long originally.

Most prior workers do not nest 
Coelurosauravus and kin with Kuehneosaurus and kin (including Xianglong from the Cretaceous. Here they do nest together and Tridentinosaurus provides clues to the clade’s arboreal origin. Apparently this is a novel hypothesis, a by-product of having so many (694) taxa in the large reptile tree (subset Fig. 2).

Figure 2. Subset of the large reptile tree showing the nesting of Tridentinosaurus at the base of the gliders, close to the drepanosaurs.

References
Dal Piaz Gb. 1932 (1931). Scoperta degli avanzi di un rettile (lacertide) nei tufi compresi entro i porfidi quarziferi permiani del Trentino. Atti Soc. Ital. Progr. Scienze, XX Riunione, v. 2, pp. 280-281. [The discovery of the remains of a reptile (lacertide) in tuffs including within the Permian quartz porphyry of Trentino.]
Leonardi P 1959. Tridentinosaurus antiquus Gb. Dal Piaz, rettile protorosauro permiano del Trentino orientale. Memorie di Scienze Geologiche 21: 3–15.
Ronchi, A., Sacchi, E., Romano, M., and Nicosia, U. 2011. A huge caseid pelycosaur from north−western Sardinia and its bearing on European Permian stratigraphy and palaeobiogeography. Acta Palaeontologica Polonica 56 (4): 723–738.