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.

---

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.

Where is the rest of Lanthanolania?

It was back in 2011
when the post-crania of Lanthanolania (Fig. 1) was reported in an abstract by Modesto and Reisz. Prior to that, in 2003, only the skull was described by the same authors. Over the last six years the post-crania of Lanthanolania has not been published.

From the 2011 SVPCA abstract:
“The evolutionary history of Diapsida during the Palaeozoic Era is remarkably poor. Following the reclassification of the Early Permian Apsisaurus witteri as a synapsid last year, only a handful of taxa span the large temporal gap between the oldest known diapsid Petrolacosaurus kansensis and the Late Permian neodiapsid Youngina capensis. These include two Middle Permian neodiapsids, the recently described Orovenator mayorum from Oklahoma, USA, and Lanthanolania ivakhnenkoi from the Mezen region, northern Russia. A recently collected, nearly complete skeleton of Lanthanolania permits a thorough reexamination of the phylogenetic relationships of these two taxa.

“Phylogenetic analysis of 188 characters and 30 diapsid taxa positions these two small forms as stem saurians and the oldest known neodiapsids (recently redefined by the authors as the sister taxon of Araeoscelidia). Interestingly, our results suggest that the lower temporal bar was lost by the ancestral neodiapsid relatively soon after the evolution of the diapsid temporal morphology, and conversely, that the temporal configuration of the Late Permian Youngina capensis is a secondary condition. In addition, the skeletal anatomy of Lanthanolania provides evidence of limb proportions that suggest that this small reptile is the oldest known bipedal diapsid.”

Figure 1. Kuehneosaurid skulls from Palaegama to Coelurosauravus and Mecistotrachelos, and to Lanthanolania, Pamelina, Kuehneosaurus, Icarosaurus and Xianglong. Some of these taxa were not previously recognized as kuehneosaurids or their ancestors.

Earlier (2011) the large reptile tree (LRT) nested Lanthanolania with the so-called rib gliders between Coelurosauravus and Icarosaurus. Back then we looked at those issues here.

Modesto and Reisz (2003) had a hard time
nesting Lanthanolania and considered it ‘enigmatic’. The closest they came was to nest Lanthanolania at the base of the lepidosauriformes (Rhynchocephalia + Squamata) and in other tests, with Coelurosauravus, which they split apart from the lepidosauriformes by adding intervening unrelated ‘by default’ taxa.

Unfortunately
with their small taxon list, Modesto and Reisz (2003) did not recover the basal split among reptiles that had occurred between the new Lepidosauromorpha and Archosauromorpha at Gephyrostegus + kin at the earliest Carboniferous. Thus the formerly monophyletic clade Diapsida is diphyletic in the LRT. Modesto and Reisz  mixed taxa from the two major clades and that muddied their results. Parts of their results were essentially correct, just unintelligible due to the addition of unrelated intervening archosauromorph basal diapsids.

Traditional paleontology
has likewise never nested coelurosauravids with kuehneosaurids, like Icarosaurus, perhaps based in part on the rib/dermal rod issue.

Problems and guesses:

1. “Phylogenetic analysis of 188 characters and 30 diapsid taxa positions these two small forms as stem saurians and the oldest known neodiapsids (recently redefined by the authors as the sister taxon of Araeoscelidia).” — Sauria (= last common ancestor of archosaurs and lepidosaurs), is a junior synonym for Reptilia in the LRT. Neodiapsida (= includes all diapsids apart from araeoscelidians (= Petrolacosaurus and Araeoscelida)) or all taxa more closely related to Youngina than to Petrolacosaurus. Thus, in their thinking, Sauria is a clade within Neodiapsida. Modesto and Reisz do not yet recognize that Diapsida is no longer a monophyletic clade. In the LRT Orovenator and Lanthanolania are not related. The former is a basal diapsid archosauromorph. The latter is a basal lepidosauriform lepidosauromorph.
2. “Interestingly, our results suggest that the lower temporal bar was lost by the ancestral neodiapsid relatively soon after the evolution of the diapsid temporal morphology,” — According to the LRT, the lower temporal bar was not lost nor was it present in the lepidosauromorph ‘rib’ gliders, including Lanthanolania. By contrast, Orovenator is one of the most basal archosauromorphs with an upper temporal fenestra.  Petrolacosaurus is older.
3. “and conversely, that the temporal configuration of the Late Permian Youngina capensis is a secondary condition.” — In the LRT, it is not a secondary configuration, but is derived from basal diapsid taxa like Orovenator.
4. “In addition, the skeletal anatomy of Lanthanolania provides evidence of limb proportions that suggest that this small reptile is the oldest known bipedal diapsid.” — I can only guess why they promoted this hypothesis: short torso and long hind limbs? Icarosaurus has such proportions. So does Kuehneosaurus. So does their last common ancestor, Palaegama (Fig. 2) which lacks wire-like dermal ossifications.

Figure 2. Palaegama, close to the origin of all Lepidosauriformes.

The question today is
where is the paper that describes the above-mentioned post-crania of Lanthanolania? Is the post-crania definitely referable?

If the referred specimen came from similar sediments
the matrix was described in 2003 as ‘extremely hard to work with’. Perhaps it is still being worked on. Or it has been shelved.

Phylogenetic bracketing
indicates that the new specimen might or should have wing-like wire/rod dermal elements, like those found in both Coelurosauravus and Icarosaurus, but traditionally considered ribs in Icarosaurus. They are not ribs, as we learned earlier here. The real ribs are short and fused to the vertebrae, appearing to be long transverse processes, but no related taxa have long transverse processes and not all of the ribs are fused to the vertebrae, betraying their identity. Since a mass of dermal rods was not mentioned in the abstract, one  wonders if the new specimen was actually closer to Palaegama than to Lanthanolania?

Late news from Sean Modesto about Lanthanolania:
“The project is currently in the hands of Dr. Reisz. No “ETA” as yet!”

Problems like this one
are a good reason to include the taxa the LRT suggests one include in smaller, more focused studies.

References:
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.
Reisz RR and Modesto SP 2011. The neodiapsid Lanthanolania ivakhnenkoi from the Middle Permian of Russia, and the initial diversification of diapsid reptiles.SVPCA abstract published online.

 

Weigeltisaurus skull reconstruction(s)

A new paper
by Bulanov and Sennikov (2015) reconstructs the holotype skull of Weigeltisaurus, a Permian gliding lepidosauriform (Fig. 1). We looked at this specimen earlier here guided by published drawings. Today we have a published photo of the specimen (see below). Previously Weigeltisaurus was considered a junior synonym of Coelurosauravus. Bulanov and Sennikov argue that Weigeltisaurus is a distinct genus.

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.

Unfortunately
Bulanov and Sennikov made so many mistakes in their reconstruction that their arguments for retaining the genus Weigeltisaurus are difficult to support. Furthermore Bulanov and Sennikov do not reference sister taxa skulls to guide them through the process of reconstruction. Sister taxa include Jesairosaurus, Palaegama and Lanthanolania. Perhaps they do not know which taxa were sister taxa. The phylogenetic nesting of Coelurosauravus is typically not associated with kuehneosaurids and the taxa listed above. Finally, a phylogenetic analysis is missing.

The present interpretation 
differs from the Bulanov and Sennikov interpretation in several regards. They missed the occiput. I traced it. They did not include supratemporals. I interpret them here, displaced toward the jaw joint in situ. The saw a postorbital that was the exact mirror image of the postorbital process of the jugal. I interpret that as the other postorbital process of the jugal, flipped along with the frontals, which are exposed ventrally through the orbit. All of the bones are closely matched by sister taxa, like Jesairosaurus and differ largely and only in the secondary sexual character, the extension of the cranial frill.

If Bulanov and Sennikov
were going to separate Weigeltisaurus from Coelurosauravus they should have presented them both side by side.

By convergence
the cranial crest of Weigeltisaurus/Coelurosauravus is similar to that of the giant dinosaur, Styracosaurus and similar to that of helmeted chameleon Trioceros hoehnelii.

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.

Jesairosaurus and the drepanosaurs leave the Tritosauria :-(

My earlier reconstruction
of the basal lepidosauriform, Jesairosaurus (Fig. 1; contra Jalil 1997, not a protorosaur/prolacertiform) included several errors based on attempting to create a chimaera of several specimens of various sizes based on scale bars. In this case, scale bars should not have been used. Rather fore and hind parts had to be scaled to common elements, like dorsal vertebrae, as shown below (Fig. 2). I think this version more accurately reflects the in vivo specimen, despite its chimeric origins. All of the partial skeletons assigned to this genus were discovered at the same Early to Middle Triassic sandstone site and two were touching one another. A larger skull, ZAR 7, shows the variation in size from the skull to shoulders remains of the ZAR 6 specimen.

Figure 1. New reconstruction of the basal lepidosauriform, Jesairosaurus (Jalil 1997). The wide and flat ribs are interesting traits for a likely arboreal reptile.

Mother of all drepanosaurs
The Drepanosauria is an odd clade of slow-moving arboreal reptiles that includes Hypuronector, Vallesaurus, Megalancosaurus and Drepanosaurus (Figs. 2, 3). Jesairosaurus was not a drepanosaur, but nested basal to this clade before the present revisions. It remains basal to the Drepanosauria now with revisions.

The revised reconstruction of Jesairosaurus 
shifts this clade away from Huehuecuetzpalli, Macrocnemus and the rest of the Tritosauria. Now Jesairosaurus and the drepanosaurs nests between Saurosternon, Palaegama and the so-called “rib” gliders, beginning with Coelurosauravus.

A short history of Jesairosaurus
Shortly after their discovery Lehman 1971 referred the several hematite encrusted specimens to the Procolophonida. Further preparation showed that they were referable to the Diapsida, according to Jalil (1990) and the, more specifically, to the Prolacertiformes (Jalil 1997) as a sister to Malerisaurus with Prolacerta as a common ancestral sister. Jalil did not include the closest sisters of Jesairosaurus as revealed by the present analysis.

With a much larger list of taxa,
the large reptile tree nests Malerisaurus between the Antarctica specimen assigned to Prolacerta (AMNH 9520) and the holotype of Prolacerta. Jesairosaurus, as mentioned above, nests with the basal lepidosauriformes. Any traits shared with protorosaurs are by convergence. Deletion of Jesairosaurus does not affect the nesting of the Drepanosauria as basal lepidosauriformes.

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

Arboreal
This new nesting shifts drepanosaurs closer to kuehneosaurs (Figs. 3, 4), another notably arboreal clade.

Figure 3. The new nesting for Jesairosaurus and the drepanosaurs as sisters to the Kuehneosaurs, several nodes away from Huehuecuetzpalli and the tritosaurs.

Certainly
there will someday be more taxa to fill in the current large morphological gaps in and around Jesairosaurus, but here’s what we have at present (Fig. 3) with regard to the origin of the so-called “rib” gliders (actually dermal rods, not ribs, as shown by Coelurosauravus) and the origin of the drepanosaurs.

Figure 4. Jesairosaurus to scale with sisters Palaegama and Coelurosauravus.

The shifting of a clade
like Jesairosaurus + Drepanosauria occurred due to inaccurate reconstructions used for data. Science builds on earlier errors and inaccuracies. I let the computer figure out where taxa nest in a cladogram of 606 possible nesting sites, minimizing the negative effects of bias and tradition.

It’s sad
to see the drepanosaurs leaving the Tritosauria as it contains several oddly Dr. Seuss-ian variations on the tritosaur theme.

Also note the nesting
of the basal Rhynchocephalians, Megachirella and Pleurosaurus, between the palaegamids and the tritosaurs (Fig. 4). In the course of this study, both also received updates to their skull reconstructions. The former was difficult to interpret without knowing where it nested. What appeared to be an odd sort of a squamosal in Megachirella now appears to be a pair of displaced pleurosaur-like premaxillae. For Pleurosaurus I should not have trusted a prior line drawing by another worker. Here I used DGS to create what appears to be a more accurate skull without so many apparent autapomorphies.

References
Jalil N 1990. Sur deux cranes de petits Sauria (Amniota, Diapsida) du Trias moyen d’ Algerie. Comptes Rendus de I’ Academic des Sciences, Paris 311 :73 1- 736.
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.
Lehman JP 1971. Nouveaux vertebres du Trias de la Serie de Zarzai’tine. Annales de Paleontologic (Vertebres) 57 :71-93.

 

 

Coelurosauravus wingless predecessor: Palaegama

Coelurosauravus (Fig. 1, Piveteau 1926, Late Permian ~250 mya, ~40 cm in length) was an arboreal lepidosauriform with an odd collection of dermal rods that opened laterally to produce ‘wings’ suitable for display or perhaps gliding. No one previously has produced an ancestor taxon.

Related taxa,
including Mechistotrachelos, Icarosaurus, Kuehneosaurus and Xianglong, produced variations on the Coelurosauravus design, all convergent with the living rib-glider, Draco, an iguanid not related to any of the above taxa.

Coelurosauravus also has wide, temporal crests shared only with Mecistotrachelos. Earlier we discussed the homology of the dermal rods (not ribs) of kuehneosaurs with those of Coelurosauravus.

Figure 1. Palaegama and Coelurosauravus to scale. The latter has dermal rods that frame gliding/display membranes. No other taxon nests closer to the base of the gliding clade.

The outgroup taxon
in the large reptile tree for these odd arborealists is Palaegama (Fig. 1, Carroll 1975). It preserves no hint of lateral dermal rods and has no temporal crest. It is such an unpopular taxon that it has not yet earned a Wikipedia entry. Among 588 taxa in the large reptile tree, no other is closer to Coelurosauravus and the kuehneosaurs.

As a basal lepidosauriform, 
Palaegama (Late Permian) also nests with the basalmost lepidosaurs, including the basalmost sphenodontid, Megachirella, the basalmost tritosaur Tijubina (Early Cretaceous) and the basalmost pre-squamate, Lacertulus (Late Permian), all ‘lizardy’ taxa of similar morphology.

So
Palaegama is really an important taxon nesting near the bases of several clades. It deserves more press, scrutiny and credit.

Distinct from predecessor taxa,
Palaegama has long strong limbs and long digits, like those of its headless sister, Saurosternon. The Palaegama skull is wide and flattened. Due to these traits it is possible that Palaegama leaped from tree to tree prior to the addition of lateral membranes stiffened with fibers.

Carroll (1975, 1977)
understood that Palaegama might have had a role in the origin of lizards, but those publications preceded computer-assisted phylogenetic analysis and Carroll was not aware of the pre-squamate and tritosaur clades, nor did he make the connection to Coelurosauravus.

A large gamut cladogram is ideal for solving many such problems.

References
Carroll RL 1975. Permo-Triassic ‘ lizards ’ from the Karroo. Palaeontologia africana 18, 71–87.
Carroll RL 1977. The origin of lizards. In Andrews, Miles and Walker [eds.] Problems of Vertebrate Evolution. Linnean Society Symposium Series 4: 359 -396.

Coelurosauravus bone identification error

A recent paper
by (Bulanov and Sennikov 2015) reinterpreted and misidentified one posterior skull bone of Coelurosauravus, the helmeted Permian glider (Figs. 1, 2).

Figure 1. Coelurosauravus. It had ribs, but no transverse processes. The extradermal rods were more numerous than the ribs. Click to learn more.

Here’s the problem:
Bluanov and Sennikov identified a triradiate bone as the jugal. Unfortunately, no kuehneosaur sister taxa in the large reptile tree have a triradiate jugal. They all lack a quadratojugal process on the jugal. The triradiate bone is the postorbital. The bone matches prior interpretations, including small triangular ossifications.

Figure 2. Coelurosauravus skull as interpreted earlier and presently. At right as reinterpreted by Bulanov and Sennikov. The mistook the triradiate and ornamented postorbital for a jugal. No sister taxa have a triradiate jugal. Click to enlarge. There were several scale bar problems as well.

References
Bulanov VV and Sennikov AG 2015. New data on the morphology of the Late Permian gliding reptile Coelurosauravus elivensis Piveteau. Paleontological Journal 49:413-423.
Carroll RL 1978. Permo-Triassic “Lizards” from the Karoo System Part II. A gliding reptile from the Upper Permian of Madagascar. Palaeontografica Africana. 21:143-159.
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). Zoological Journal of the Linnean Society 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.
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
Piveteau J 1926. Paleontologie de Madagascar, XIII. Amphibiens et reptiles permiens: Annales de Paleontologie, v. 15, p. 53-128.

wiki/Coelurosauravus
wiki/Mecistotrachelos

Icarosaurus fingers!

At first glance
it looks like only one digit (digit 1, including its big ungual) is visible in the manus of Icarosaurus (Colbert 1966). But add some colors to the bones (DGS) and the extra bits and pieces make themselves known.  Apparently the fingers were tucked under the metacarpus (Fig. 1). The reconstruction matches the manual phalangeal patterns of other kuehneosaurs, including Coelurosauravus, Kuehneosaurus and Xianglong, adding confidence to the reconstruction that also had continuous PILs.

Figure 1. Icarosaurus fingers were tucked under the metacarpus. Colorized and reconstructed using DGS.

References
Colbert, Edwin H. (1966). A gliding reptile from the Triassic of New Jersey. American Museum Novitates 2246: 1–23. online pdf

wiki/Icarosaurus

Rhynchosauroides hyperbates: what a handprint!

Figure 1. Rhynchosauroides hyperbates manus (Late Triassic). Note the perfect impression of tiny scales here, along with toe drag marks and the lineup of the metacarpals with 2 and 3 longer than 4, very rare among reptiles. Like Rotodactylus digit 1 barely impresses. Unlike Rotodactylus, digit 5 impresses laterally here. Unlike the holotype, here the palm is impressed.

I found this image of a pristine Late Triassic manus ichnite online here and wanted to know which Late Triassic genus or family it might belong to. I found out it was referred to Rhynchosauroides hyperbates by Roy Schlische (1996). Here is his abstract.

“Previously known only from the holotype from the lower Passaic Fm. (E. Norian), segments of a superb long trackway of R. hyperbates have been recovered from a roadcut for the Schuylkill Expressway through the Lockatong Fm. (L. Carnian) of the Newark basin. Walking and swimming trackways as well as resting belly impressions are present, all with remarkably detailed skin impressions. Composite drawing of the manus and pes using the methodology of Baird confirm his original interpretations of the skeletal reconstruction. Cladistic analysis of the reconstruction shows that the trackmaker had feet of the primitive diapsid pattern. Consideration of the range of diapsids known from the Triassic suggests that a sphenodontid was the most likely trackmaker, as Baird observed.” 

Schlische, referred me to two students now working with it, but they did not respond.  Triassic expert Paul Olsen referred me to Olsen and Flynn 1989. Another paper on this trackway is on its way to publication. I understand this image once graced the cover of Science magazine in 1989. Yes, it’s that good!

Noteworthy in the image above, 
m1.1 apparently was kept within the fleshy body of the other metatarsals according to the ichnite. Who knew?? But it makes a certain sense considering the length of mc2.

A little about the ichnogenus Rhynchosauroides
There are several ichnospecies associated with the ichnogenus Rhynchosauroides, which is found worldwide. From all I can gather, it is a wastebasket ichnogenus most commonly employed for lepidosauromorph traces typically defined by a relatively longer digits laterally.

Figure 2. The trackway of Rhynchosauroides hyperbates as originally compared to a trackmaker (below) and here compared to a relatively smaller living lizard in dorsal view.

Figure 3. The holotype of Rhynchosauroides,  ANS 15210 (upper left), is a much smaller specimen. Referred specimens by Baird (larger images above) do not have a short mt4. Rather they have a more standard asymmetrical metatarsus. Plus, these are all digitigrade impressions, unlike figure 1. So, based on these differences the unknown image in Figure 2 does not appear to be similar to these. But then, there were many more tracks found around Rhynchosauroides hyperbates and some of them may more closely resemble these.

Type specimen:
ANS 15210, is the ichnogenus holotype (Fig. 3) and the type locality is Smith Clark’s quarry (tracks), Milford, level B, which is in a Norian terrestrial shale/sandstone in the Passaic Formation of New Jersey.

Figure 4. Click to enlarge. Rhynchosauroides tyrolicus (Avanzini and Renesto 2002) along with their paper models of the digitigrade manus and pes, their reconstruction of the Macrocnemus-like trackmaker (gray), and their posterior view of a walking lizard (blue). Note the left pes is still not planted while the left manus is planted. I have rearranged the limbs of their trackmaker to match the tracks and match the lepidosaur in blue. Note this is a distinctly different ichnospecies.

Rhynchosauroides tyrolicus,
another species of Rhynchosauroides from the Triassic of Europe, was closely matched to Macrocnemus by Avanzini and Renesto 2002. I think they did a great job, employing a cut paper pes model to discover a better match in 3D to the digitigrade traces. This simple yet effective technique was also used in Peters 2000a, b. Avanzini and Renesto 2002 provided a reconstruction Fig. 2 in gray) that matched the footprints, but it was an odd configuration requiring the left pes to overtake the left manus before the left manus could lift off the substrate. An alternative is offered (Fig. 2 in black) that more closely matches the movement of an actual lepidosaur images (Fig. 2 in blue) published by Avanzini and Renesto 2002 showing the left manus and right pes in contact with the substrate at one point. This would also match the trackway. It’s the same step cycle. Just the timing is shifting a little. Then again, in figure 2, the pose is virtually the same as figured by Avanzini and Renesto.

Digitigrady
A digitigrade Macrocnemus phylogenetically precedes a digitigrade Cosesaurus (matched to digitigrade Rotodactylus traces) at the base of the other fenestrasaurs, including pterosaurs, now shown to have produced digitigrade traces in the Late Triassic.

The ichnogenus Rhynchosauroides
A wide variety of lepidosaur-ish traces have been assigned to the wastebasket Rhynchosauroides. Now that Macrocnemus nests with the tritosaur lepidosaurs, this ichnotaxon also extends to the tritosaurs.

References
Avanzini M and Renesto S 2002. A review of Rhynchosauroides tyrolicus Abel, 1926 ichnospecies (Middle Triassic: Anisian-Ladinian) and some inferences on Rhynchosauroides trackmaker. Rivista Italiana di Paleontologia e Stratigrafia 108(1):51-66.
Baird D 1957. Triassic reptile footprint faunules from Milford, New Jersey. Bulletin of the Museum of Comparative Zoology117(5):449-520.
Olsen PE and Flynn JJ 1989. Field Guide to the Vertebrate Paleontology of Late Triassic Age Rocks in the Southwestern Newark Basin (Newark Supergroup, New Jersey and Pennsylvania. The Mosasaur 4:1-43, Delaware Valley Paleontological Society.
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: 293-336.
Schlische RW 1996. Uniquely preserved trackway of the reptile ichnotaxon Rhynchosauroides hyperbates BAIRD from the Late Triassic of Arcola, Pennsylvania, associated forms, and significance to Carnian-Norian extinction online abstract

Yes, they’re all kuehneosaurids, or their ancestors.

The kuehneosaurids, arboreal gliding lepidosauriforms, have an interesting pedigree. Tradition holds that they appeared suddenly without precedent and, until recently, only two genera were recognized, Icarosaurus and Kuehneosaurus (Fig. 1), both from the Late Triassic. By contrast, the large reptile tree found an extended evolutionary lineage that we looked at earlier. Here we’ll look at the skulls in sequence, talk about the new kuehneosaur, Pamelina, and discuss the reptile family tree.

Figure 1. Kuehneosaurid skulls from Palaegama to Coelurosauravus and Mecistotrachelos, and to Lanthanolania, Pamelina, Kuehneosaurus, Icarosaurus and Xianglong. Some of these taxa were not previously recognized as kuehneosaurids or their ancestors.

Gliding struts and lateral extradermal membranes probably first appeared as decorations because the skull of Coelurosauravus (Fig. 1) is also distinctly decorated with a squamosal/supratemporal frill. Mecistotrachelos (Fig. 1) kept its frill. The others did not. The frill-less taxa also lose the supratemporal, a bone that makes up the back part of the frill. Palaegama has no dermal struts. Lanthanolania is known by a skull only. Pamelina vertebrae (Fig. 2) do not have the long fused transverse processes of Kuehneosaurus.

Widely considered to glide with hyper-elongated ribs, the lineage of kuehneosaurids indicates that those ribs were actually ossified dermal filaments/bones (as seen in Coelurosauravus, Fig. 1). The ribs shrank (Fig. 2) and disappeared and in their place grew elongated transverse processes to act as anchors for the gliding struts. This happened by convergence twice, once in Mecistotrachelos and again in the lineage of kuehneosaurids without a frill. You can see the transformation in Kuehneosaurus and Pamelina (Fig. 2).

Figure 2. Above, sample vertebrae from Pamelina. Below, the more derived Kuehneosaurus. True ribs are shown in yellow. Dermal struts are in blue. Note the lack of fused transverse processes on the dorsal vertebrae in Pamelina. The elongated caudal transverse processes indicate the presence of a large caudofemoral muscle, which would have been much smaller in Kuehneosaurus.

A paper by Evans (2009)
described Pamelina (Fig. 1), an early Triassic kuehneosaurid added a third genus to her list of kuehneosaurs. Note the lack of fused transverse processes on the dorsal vertebrae in Pamelina. The elongated caudal transverse processes indicate the presence of a large caudofemoral muscle, which would have been much smaller in Kuehneosaurus.

Other members
Earlier we also added Xianglong (which is not a lizard), and Lanthanolania (which is not a younginoid) along with Coelurosauravus (Fig.1), which everyone else thinks developed rib membranes by convergence.

Family Tree
Evans (2009) produced an interesting family tree of the Reptilia. Except for turtles it splits reptiles into two main lineages, one that includes lepidosaurs and one that includes archosaurs, like the large reptile tree does. Of course the tree by Evans assumes the outgroups and basal taxa include synapsids, which nest in the archosaur half of the large reptile tree.

Figure 2. Reptile tree according to Evans 2009, that is very much in line with the large reptile tree, except for the nesting of turtles (probably due to shelled placodonts) near Sauropterygians. Blue = the new epidosauromorphs. Yellow = the new archosauromorphs.

The current state of phylogenetic thinking
Evans (2009) reports, “The Neodiapsida of Benton (1985) encompasses a wide range of diapsid lineages, most of which can be assigned to either Archosauromorpha or Lepidosauromorpha (Gauthier et al. 1988). Archosauromorpha encompasses a large and successful crown clade (Archosauria) and a series of distinctive stem lineages (e.g., protorosaurs, tanystropheiids, Prolacerta, Rhynchosauria, Trilophosauria, Evans 1988; Gauthier et al. 1988; Müller 2002, 2004; Modesto and Sues 2004). Crown−group Lepidosauria (Rhynchocephalia and Squamata) also constitutes a large and diverse group but, leaving aside the issue of testudine or sauropterygian affinities (e.g., Rieppel and de Braga 1996; de Braga and Rieppel 1997; Rieppel and Reisz 1999; Müller 2002, 2004; Hill 2005).”

By contrast the large reptile tree found those listed members of Evans’ “Neodiapsida” to be diphyletic and found the lepidosauromorpha also include tanystropheids, Rhynchosauria and Trilophosauria along with turtles.

We’re working for consensus, but first others have to expand their inclusion set gamut and avoid suprageneric taxa.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Evans SE 2009. An early kuehneosaurid reptile from the early Triassic of Poland. Palaeotologia Polonica 65: 145-178.

Mecistotrachelos, the Walking Stick “Rib” Glider

Among the Permo/Triassic so-called “rib” gliders is an oddball with a walking-stick sort of torso with fused ribs no wider than its centra. The oddball is Mecistotrachelos from the Late Triassic and it was a sister to Coelurosauravus of the Late Permian.

Figure 1. Mecistotrachelos, the walking stick "rib" glider in lateral view except for the dorsal series and pseudoribs, which are seen in dorsal view. pseudoribs folded above, and extended below. The tail length is unknown.

Mecistotrachelos apeoros (Fraser et al. 2007) Late Triassic ~210 mya, demonstrates variety in later derived clade members with fewer dorsal vertebrae and fewer pseudoribs. The body was extremely slender, almost stick-like, with hyper-elongated cervicals and greatly reduced ribs fused to each centrum. The limbs were more gracile and the tail length is unknown. The fibula was fused or closely adhered to the tibia.

The long neck would have made Mecistotrachelos an unstable glider according to Fraser (2007). Coelurosauravus had a long neck and a larger skull. Were the dermal struts deployed for gliding? For display? Or both? Like other kuehneosaurs, Mecistotrachelos had small teeth and was likely an insectivore. Fraser (2007) wondered if his find was an archosauromorph. It is not. Here Mecistotrachelos nested with Coelurosauravus among the lepidsauromorpha, within the lepidosauriformes.

Not Like Draco the Extant Glider
Fraser (2007) reported, “The new form is characterized by the presence of extremely elongate thoracolumbar ribs that presumably supported a gliding membrane in life.” Fraser (2007) notes kuehneosaurs had “ribs forming hinge joints with the markedly elongate transverse processes on the dorsal vertebrae.” This is wrong. No Mecistotrachelos sister taxa had elongated transverse processes. The apparent transverse processes ARE the ribs, fused to the vertebrae, derived from the condition seen in the short ribs of Coelurosauravus (Fig. 2). The pseudoribs were actually elongated dermal ossicles described as “bundles of rodlike neomorph ossifications,” by Fraser (2007) quoting Frey et al. (1997). By contrast, in Draco the gliding struts are indeed elongated dorsal ribs.

Figure 2. Click to enlarge. The Triassic gliders and their non-gliding precursors.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
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.

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