Nycteroleter: which data is better?

Nycteroleter
(Efremov 1938; Middle Permian) was just added to the large reptile tree (LRT, 1035 taxa). The GIF movie shown here (Fig. 1) shows the data I had to work with. Note the differences.

Figure 1. Nycteroleter inept us and the two data sources used in scoring this taxon. The one with the smaller premaxilla in dorsal view nests with fewer autapomorphies in the LRT.

Figure 1. Nycteroleter inept us and the two data sources used in scoring this taxon. The one with the smaller premaxilla in dorsal view nests with fewer autapomorphies in the LRT.

This is not a case of ‘who do you trust?’
because we can figure out which is the more accurate skull by using the LRT.

I let the LRT choose which dataset
had fewer autapomorphies, since I had no direct access to fossils. Note the less accurate skull also mislabels the cranial corners as tabulars. They should be labeled supratemporals. Nycteroleter nests with Nyctiphruretus in the LRT.

If I’m wrong, 
I’ll make the changes if and when better data comes in.

References
Efremov JA 1938. Some new Permian reptiles of the U.S.S.R. Comptes Rendus (Doklady), 19: 771–776.

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Shringasaurus: new rhynchocephalian lepidosaur with horns

Sengupta, Ezcurra and Bandyopadhyay 2017 bring us
a new, very large, horned rhynchocephalian lepidosaur, Shringasaurus (Fig. 1). Unfortunately, that’s not how the Sengupta team nested it (due to the sin of taxon exclusion, see below). Even so, there is consensus that the new taxon is closely related to the much smaller Azendohsaurus (Fig. 1).

Figure 1. Shringasaurus to scale with Azendohsaurus. Line art modified from Sengupta et al. Color added here. Note the anterior lappet of the maxilla over the premaxilla. The supratemporal  (dark green) remains.

Figure 1. Shringasaurus to scale with Azendohsaurus. Line art modified from Sengupta et al. Color added here. Note the anterior lappet of the maxilla over the premaxilla. The supratemporal  (dark green) remains.

From the abstract:
“The early evolution of archosauromorphs (bird- and crocodile-line archosaurs and stem-archosaurs) represents an important case of adaptive radiation that occurred in the aftermath of the Permo-Triassic mass extinction. Here we enrich the early archosauromorph record with the description of a moderately large (3–4 m in total length), herbivorous new allokotosaurian, Shringasaurus indicus, from the early Middle Triassic of India. The most striking feature of Shringasaurus indicus is the presence of a pair of large supraorbital horns that resemble those of some ceratopsid dinosaurs. The presence of horns in the new species is dimorphic and, as occurs in horned extant bovid mammals, these structures were probably sexually selected and used as weapons in intraspecific combats. The relatively large size and unusual anatomy of Shringasaurus indicus broadens the morphological diversity of Early–Middle Triassic tetrapods and complements the understanding of the evolutionary mechanisms involved in the early archosauromorph diversification.”

Allokotosauria
Shringasaurus was nested in the clade, Allokotosauria, According to Wikipedia, “Nesbitt et al. (2015) defined the group as a  containing Azendohsaurus madagaskarensis and Trilophosaurus buettneri and all taxa more closely related to them than to Tanystropheus longobardicus, Proterosuchus fergusi, Protorosaurus speneri or Rhynchosaurus articeps.” This definition was based on the invalidated hypothesis that rhynchosaurs and allokotosaurs were close to the base of the Archosauriformes as the addition of more taxa will demonstrate. Basically this clade equals Trilophosaurus, Azendohsaurus and now Shringasaurus. In the large reptile tree (LRT, 1049 taxa) this clade nests between Sapheosaurus + Notesuchus and Mesosuchus + Rhynchosauria all nesting within Sphenodontia (=  Rhynchocephalia), so they are all lepidosaurs. All you have to do is add pertinent taxa to make this happen in your own phylogenetic analysis.

Figure 2. Scene from the 1960 film, The Lost World, featuring a giant iguana with horns added presaging the appearance of Shringasaurus.

Figure 2. Scene from the 1960 film, The Lost World, featuring a giant iguana with horns added presaging the appearance of Shringasaurus.

Coincidentally the 1960 film,
The Lost World featured an iguana made up with horns similar to those of Shringasaurus.

References
Sengupta S, Ezcurra MD and Bandyopadhyay S 2017. A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India. Nature, Scientific Reports 7: 8366 | DOI:10.1038/s41598-017-08658-8 online here.

No Wiki page yet.

Tulerpeton: transitional from Ichthyostega to Eucritta

This post was updated February 24, 2017, after new data on Tulerepton became available. And again on December 13, 2017. 

This latest nesting 
of the former basal tetrapod, Tulerpeton (Fig. 2), as a Devonian transitional taxon leading to the Amphibia, the Reptilia and the Seymouriamorpha in the large reptile tree (1134 taxa) was both anticipated (Fig. 1) and welcome.

As you may recall…
Middle Devonian tetrapod trackways (preceding and coeval with the basal bony fish Cheirolepis and the lobe fins Eusthenopteron and Osteolepis) seemed anachronistic when first announced. But it’s all coming together now. And this new nesting adds precious time for evolution to produce the variety of amphibian-like reptiles present in the Viséan, still awaiting consensus confirmation of their reptilian status.

Figure 1. The nesting of Tulerpeton in the Latest Devonian, at the base of the Lepidosauromorpha.

Figure 1. The nesting of Tulerpeton in the Latest Devonian, at the base of the Lepidosauromorpha. This taxon was added to this graphic that was published online in August 2016.

According to Wikipedia
Tulerpeton curtum
(Lebedev 1984, Fammenian, Latest Devonian, 365 mya; Fig. 1) is “one of the first true tetrapods to have arisen.” It was distinct from less derived Acanthostega and Ichthyostega by a strengthened limb structure. It was also half to an eighth the size of these basal tetrapods. A fragmented skull is known for Tulerpeton, but the only fragment I’ve seen is a vague round premaxilla on small reconstructions. Both the manus and pes have 6 digits, all provided with clawed unguals. (NOTE ADDED MARCH 6, 2017: The pes has only five digits after a fresh reconstruction)

FIgure 1. Tulerpeton compared to Eldeceeon.

FIgure 2. Tulerpeton compared to similarly-sized Eldeceeon. The loss of one digit in the manus and pes occurred between the Fammenian and Viséan.

Tulerpeton lived in shallow marine waters.
Little is known of this Eldeceeon-sized specimen, but the limbs and pectoral girdle are fairly well preserved. And these were enough to nest it between Ichthyostega and Eucritta among 1133 taxa in the LRT.

Coates and Ruta 2001 report:
“The most taxon-inclusive crown hypothesis incorporates the hexadactylous Late Devonian genus Tulerpeton as a basal stem amniote, thereby pegging the lissamphibian amniote divergence to a minimum date of around 360 Ma.” So there were early rumors. Only taxon exclusion prevented prior workers from recovering the reptile relationship earlier, no doubt due to the six fingers and toes on this putative basal tetrapod.

The loss of the sixth digit
occurred more than once, just as the later loss of a fifth digit occurred more than once. We should look for taxa with six fingers at the base of the Reptilomorpha and Seymouriamorpha — unless Tulerpeton developed a sixth finger on its own.

Phylogenetic analysis
originally placed Tulerpeton near the base of reptilomorphs, like Proterogyrinus and Eoherpeton. Later workers nested it as a more basal member of the Tetrapoda, between Acanthostega and Greererpeton.

Here
those long, clawed fingers and toes, and the individual proportions of the metapodials and phalanges nested Tulerpeton between Ichthyostega and Eucritta in the LRT.

Major studies do not yet recognize the reptile status
of Gephyrostegus. Hopefully someone will add them and Eldeceeon to a future taxon list to confirm or refute the present findings.

References
Coates MI and Ruta M 2001 (2002). Fins to limbs: What the fossils say. Evolution & Development 4(5): 390–401.
Lebedev OA 1984. The first find of a Devonian tetrapod in USSR. Doklady Akad. Navk. SSSR. 278: 1407–1413.
Lebedev OA and Clack JA 1993. Upper Devonian tetrapods from Andreyeva, Tula Region, Russia. Paleontology36: 721-734.
Lebedev OA and Coates MI 1995. postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev. Zoological Journal of the Linnean Society. 114 (3): 307–348.

wiki/Tulerpeton

Magnuviator, another basal scleroglossan.

A recent paper brings us
a Late Cretaceous “iguanomorph,” Magnuviator ovimonsensis (DeMar et al. 2017). It nested with Saichangurvel originally and here in the LRT, but both nest in the LRT with Acanthodactylus at the base of the Scleroglossa, not within the Iguania. The authors provided illustrations of the in situ fossils which I have restored to the in vivo configuration (Fig. 1) more or less.

Figure 1. Magnuviator ovimonsensis in situ from DeMar et al. 2017) and in vivo.

Figure 1. Magnuviator ovimonsensis in situ from DeMar et al. 2017) and in vivo.

DeMar et al.
added Magnuviator to the cladogram provided by Conrad 2008. Earlier we looked at the problems therein and in other earlier studies. As in the earlier Saichangurvel study, Magnuviator nests close enough to the clade Iguania that there are no intervening taxa.

References
DeMar Jr DG, Conrad JL, Head JJ, Varricchio DJ and Wilson GP 2017. A new Late Cretaceous iguanomorph from North America and the origin of New World
Pleurodonta (Squamata, Iguania). Proc. R. Soc. B 284: 20161902.

Lacerta: where is the upper temporal fenestra?

Lacerta viridis (Fig. 1) is a common extant lizard that has more skull bones than is typical for most tetrapods. It also loses the upper temporal fenestra found in other lizards, by posterior expansion of the postfrontal.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

This Digimorph.org image
was colorized in an attempt at understanding the skull bones present here. The extant Lacerta nests with the larger extinct Eolacerta in the large reptile tree (918 taxa).

40 species are known of this genus.
Fossils are known from the Miocene (Čerňanský 2010). The tail can be shed to evade predators. This lizard is an omnivore. The curled quadrate frames an external tympanic membrane (eardrum). With the premaxillae fused, Lacerta has nine premaxillary teeth, with one in the center.

Not sure why this lizard developed extra skull bones.
It is found in bushy vegetation at woodland and field edges, and is not described as a burrower or a head basher.

Other diapsid-grade reptiles that nearly or completely lose the upper temporal fenestra include:

  1. Mesosaurus
  2. Chalcides
  3. Acanthodactylus
  4. Phyrnosoma
  5. Minmi

References
Čerňanský A 2010. Earliest world record of green lizards (Lacertilia, Lacertidae) from the Lower Miocene of Central Europe. Biologia 65(4): 737-741.
Linnaeus C 1758.
Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

Lacerta viridis images online
wiki/Lacerta

Saichangurvel: not an iguanid, but very close…

This appears to be yet another case of a priori taxon exclusion.
Saichangurvel davidsoni (Conrad and Norell 2007; (IGM 3/858; Late Cretaceous) was originally considered a member of the Iguania, but here nests with Acanthodactylus, a lacertid taxon not mentioned in the original text, but nesting as a sister to the Iguania and is a basalmost scleroglossan.

Conrad and Norell report
“Iguania, like Squamata as a whole, has a rich, but patchy fossil record. Although many Cretaceous species have been identified, Saichangurvel davidsoni is the first known from a complete skeleton. Indeed, the recent revelation that none of the Euposaurus remains may be diagnosed as iguanians (Evans, 1993) renders Saichangurvel davidsoni the earliest iguanian known from complete remains.”

Contra Evans 1993
The LRT nests tiny Euposaurus with the much larger Iguana (Fig. 2) as yet one more example of phylogenetic miniaturization at the genesis of major clades. In this case the major clades are Iguania and Squamata. BTW the ResearchGate.net link for Euposaurus takes you to another SE Evans paper.

Distinct from Acanthodactylus,
the teeth of Saichangurvel have three cusps, convergent with Iguana and that may be why the specimen was originally nested with iguanids. The upper temporal fenestrae are not reduced by a posterior extension of the postfrontal. Acanthodactylus has simple cone-shaped teeth.

Figure 1. Saichangurvel in situ, a complete squamate originally considered a member of Iguania but here nesting with Acanthodactylus.

Figure 1. Saichangurvel in situ, a complete squamate originally considered a member of Iguania but here nesting with Acanthodactylus.

The large reptile tree
(LRT) nests Saichangurvel very close to the Iguania (Fig. 2 in pink), but not in that clade. Unfortunately two of the top lizard experts in the world, Conrad and Norell, excluded taxa pertinent to the analysis, like Acanthodactylus and other basal scleroglossans (Fig 2 in green), That’s my only trump card here.

Figure 2. Subset of the LRT focusing on the Iguania and basal Scleroglossa, including Acanthodactylus and Saichangurvel

Figure 2. Subset of the LRT focusing on the Iguania and basal Scleroglossa, including Acanthodactylus and Saichangurvel

References
Conrad JL and Norell MA 2007. A complete late Cretaceous Iguanian (Squamata, Reptilia) from the Gobi and Identification of a new iguanian clade. American Novitates 3584:1-47.
Daza JD, Abdala V, Arias JS, Garcia-Lopez D and Ortiz P 2012. Cladistic Analysis of Iguania and a Fossil Lizard from the Late Pliocene of Northwestern Argentina”. Journal of Herpetology. 46(1):104-119.
Evans SE 1993. A re-evaluation of the Late Jurassic (Kimmeridgian) reptile Euposaurus (Reptilia: Lepidosauria) from Cerin, France. Geobios 27: 621–631.

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

Figure 1. Extant Draco flying with hands either grabbing the leading edge of the membrane or streamlining their hands on top of it.

Figure 1. Extant Draco flying with hands either grabbing the leading edge of the membrane or streamlining their hands on top of 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.

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.

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.