Burrowing squamates: Ebel et al. 2020 examines bone micro-anatomy

From the Ebel et al 2020 abstract:
“We reconstructed the acquisition of a fossorial lifestyle in 2813 lepidosaurs and assessed the skull roof compactness from microCT cross-sections in a representative subset (n = 99). We tested this and five macroscopic morphological traits for their convergent evolution. We found that fossoriality evolved independently in 54 lepidosaur lineages. Furthermore, a highly compact skull roof, small skull diameter, elongate cranium, and low length ratio of frontal and parietal were repeatedly acquired in concert with a fossorial lifestyle.”

Unfortunately the Ebel team relied on a genomic cladogram. By contrast the large reptile tree (LRT, 1772+ taxa, subset Fig. 2) found only 6 lepidosaur fossorial clades. Perhaps this is so because the LRT is a phenomic (trait-based) cladogram in which fossorial and legless Dibamus is a highly derived skink, alongside Bipes and Amphisbaena, not a basalmost squamate nesting alone. In the LRT, basalmost squamates have legs, fingers and toes, traits many derived squamates retain then lose.

Figure 1. Cladogram of burrowing (fossorial) squamates from Ebel et al. 2020. Compare to figure 2 from the LRT.

Figure 1. Cladogram of burrowing (fossorial) squamates from Ebel et al. 2020. Compare to figure 2 from the LRT.

Ebel et al 2020 abstract continues:
“We report a novel case of convergence that concerns lepidosaur diversity as a whole. Our findings further indicate an early evolution of fossorial modifications in the amphisbaenian ‘worm-lizards’ and support a fossorial origin for snakes.”

By contrast the LRT employs a wider gamut of taxa, including fossils, and finds a basal dichotomy at the genesis of snakes. One branch remained terrestrial while the other branch became fossorial. The morphologically weirdest burrowing snakes are the most derived. That’s how evolution works: from simple and plesiomorphic to bizarre and derived.

The latest LRT addition to snakes, Atractaspis, is a burrowing venomous snake arising from terrestrial snakes. That taxon would have been overlooked prior to addition to the LRT, so there may be other squamate burrowers not yet tested by the LRT.

Figure 2. Subset of the LRT focusing on Squamata. Compare to Ebel et al. 2020 in figure 1.

Figure 2. Subset of the LRT focusing on Squamata. Compare to Ebel et al. 2020 in figure 1.

The LRT finds only six clades
of burrowing squamates (Fig. 2) and an entirely different tree topology that includes fossils and protosquamates, and, need I say it, tritosaurs.


References
Ebel R, Müller J, Ramm T, Hipsley C and Amson E 2020. First evidence of convergent lifestyle signal in reptile skull roof micro anatomy. BMC Biology 18…185. https://doi.org/10.1186/s12915-020-00908-y

Uma, the fringe-toed lizard, enters the LRT

Uma is the extant fringe-toed lizard
(Fig. 1). This California desert specimen has a large orbit, much larger than the eyeball.

Figure 1. Skull of Uma, the fringe-toed lizard, plus face and in situ photo.

Figure 1. Skull of Uma, the fringe-toed lizard, plus face and in situ photo.

Uma inornata (Baird 1859) is the extant fringe-toed lizard, an insectivore. Flaps and interlocking scales prevent sand from entering the nose, mouth, eyes and ears. In the large reptile tree (LRT, 1707+ taxa) Uma nests with another desert lizard, Phrynosoma (Fig. 2). This clade nests with chameleons within the Iguania within the Squamata. No surprises here. Everyone agrees to this.

Figure 6. Phyronosoma, the horned lizard of North America.

Figure 2. Phyronosoma, the horned lizard of North America.

The addition of Uma to the LRT
and the few corrections made to scores in nearby taxa moved the following three former Early Cretaceous protosquamates to the squamates: Indrasaurus, Hoyalacerta, and Meyasaurus. These now nest basal to Yabeinosaurus within Scleroglossa. So generalized are these three taxa, they now also nest as sisters to the gekko + snakes and their ancestors clade.

This is how the LRT nests taxa
without bias, myth or tradition.


References
Baird SF 1859. Description o new genera an species of North American lizards in the Museum of the Smithsonian Institution. Proceedings of the Academy of Natural Science: 253–256.

wiki/Fringe-toed_lizard
digimorph./Uma_scoparia/

Megaevolutionary dynamics in reptiles: Simoes et al. 2020

Simoes et al 2020 discuss
“rates of phenotypic evolution and disparity across broad scales of time to understand the evolutionary dynamics behind the origin of major clades, or how they relate to rates of molecular evolution.”

“Here, we provide a total evidence approach to this problem using the largest available data set on diapsid reptiles.”

Unfortunately not large enough to understand that traditional ‘diapsid’ reptiles are diphyletic, splitting in the Viséan and convergently developing two

“We find a strong decoupling between phenotypic and molecular rates of evolution,”

Yet another case of gene-trait mismatch in analysis.

“and that the origin of snakes is marked by exceptionally high evolutionary rates.”

Taxon exclusion is the reason for this exclusion.

Figure 1. Cladogram from Simoes et al. 2020. Gray tones added to show Lepidosauromorpha in the LRT.

Figure 1. Cladogram from Simoes et al. 2020. Gray tones added to show Lepidosauromorpha in the LRT.

“Here, we explore megaevolutionary dynamics on phenotypic and molecular evolution during two fundamental periods of reptile evolution: i) the origin and early diversification of the major lineages of diapsid reptiles (lizards, snakes, tuataras, turtles, archosaurs, marine reptiles, among others) during the Permian and Triassic periods,”

In the LRT the new archosauromorphs split from new lepidosauromorphs in the Viséan (Early Carboniferous).

“as the origin and evolution of lepidosaurs (lizards, snakes and tuataras) from the Jurassic to the present.”

In the LRT lepidosaurs had their origin in the Permian and the Simoes team ignores the Triassic radiation of lepidosaurs leading to tanystropheids and pterosaurs.

So without a proper and valid phylogenetic context,
why continue? How can they possibly discuss ‘rates of change’ if they do not include basal taxa from earlier period?

“Our results indicating exceptionally high phenotypic evolutionary rates at the origin of snakes further suggest that snakes not only possess a distinctive morphology within reptiles,  but also that the first steps towards the acquisition of the snake body plan was extremely fast.”

In the LRT many taxa are included in the origin of snakes from basal geckos. These are missing from Simoes list of snake ancestor.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

In the LRT all sister taxa resemble one another
and document a gradual accumulation of derived traits.

If you have any particular evolutionary questions,
they were probably answered earlier in previous posts. Use the keyword box at upper right to seek your answer.

 

Recalibrating clade origins, part 3

Earlier
we looked at the first part and second part of Marjanovic’s 2019 chronological recalibration of vertebrate nodes.  Today we continue.

Testudines (Panpleurodira – Pancryptodira)
Unfortunately Marjanovic relies on tradition when he splits turtles into pleurodiran (side-neck) and cryptodiran (hidden-neck) clades. He reports, “With one short series of exceptions (Gaffney et al., 2006, 2007; Gaffney and Jenkins, 2010), all treatments of Mesozoic turtle phylogeny from the 21st century have consistently found Proterochersis and all other turtles older than Late Jurassic to lie outside the crown group. The oldest known securely dated crown-group turtle is thus the mid-late Oxfordian (158 Ma) stem-panpleurodire Caribemys. The observed absence of cryptodires is likely real; combining this with more rootward Middle and Early Jurassic stem turtles from other continents, I suggest a hard maximum age of 175 Ma based on the beginning of the Middle Jurassic (174.1 ± 1.0 Ma ago: ICS).”

Neither sea turtles nor soft-shell turtles hide their head within their carapace, nor could their ancestors do so. In the large reptile tree (LRT, 1630+ taxa; Fig. 1) the basal dichotomy between soft shell and hard shell turtles extends back to small horned pareiasaurs from the Latest Permian (255 mya). Thus the crown group of all living turtles also includes all extinct turtles. Cryptodires and pleurodires appeared later, both within the hardshell clade, timed as noted above.

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Lepidosauria (Rhynchocephalia + Squamata)
Marjanovic reports, “The minimum age of this calibration, given as 238 Ma, has to be slightly revised to 244 Ma (hard) based on Megachirella, the oldest known stem-squamate, which is older than the oldest known rhynchocephalian (238–240 Ma). An Early Triassic or perhaps Late Permian maximum age seems reasonable, but, given the rarity of stem-lepidosauromorphs and of Permian diapsids in general, I rather propose to use the ecologically similar small amniotes of Richards Spur (289 ± 0.68 Ma, see Node 107) to support a soft maximum age of 290 Ma.”

In the LRT the last common ancestors of rhynchocephalians + squamates (Fig. 2) include the basal rhynchocephalian (not stem-squamate) Megachirella (earliest Middle Triassic, 244 mya) and the earlier Palaegama (Late Permian). A proximal outgroup taxon is Tridentinosaurus (Earliest Permian, 295mya) approximating Marjanovic’s proposal.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

Toxicofera (Pythonomorpha + Anguimorpha including Iguanomorpha)
Marjanovic reports, “I agree with Irisarri et al. (2017) in not assigning a maximum age other than that for Node 125 (Lepidosauria, see above).”

In the LRT Toxicofera is a junior synonym for Squamata (Fig. 2). The basalmost squamate taxon in the LRT is Euposaurus (Late Jurassic, Kimmeridgian, 155 mya). An Early Permian outgroup taxon, MNC-TA1045 (Spindler 2017) in a traditionally unrecognized clade, Protosquamata, which includes extinct taxa only. Lacertulus (Late Permian, not mentioned by Marjanovic) is a basal taxon.

Iguania (Chamaeleonformes + Iguanoidea)
Marjanovic reports, “I cannot assign a maximum age other than that for Node 125.” (See above).

In the LRT Euposaurus (overlooked by Marjanovic, and see above, Fig. 2), is the basalmost member of the Iguania and Squamata.

More tomorrow…


References
Marjanovic D 2019. Recalibrating the transcriptomic timetree of jawed vertebrates.
bioRxiv 2019.12.19.882829 (preprint)
doi: https://doi.org/10.1101/2019.12.19.882829
https://www.biorxiv.org/content/10.1101/2019.12.19.882829v1

Squamate genes show ‘no support’ for key traditional morphological relationships

If squamate genes showed ‘no support’
for key traditional morphological relationships, that was a red flag that Burbrink et al. 2019 chose to ignore. Instead they put their faith in genes instead of the measurable evidence of traits. As we’ve seen many times before, something is wrong with deep time genetic testing, hobbled from the starting blocks by not including fossil taxa. No gene test has ever revealed that a jugal is absent or present, that a metatarsal is longer than the toe or shorter. Whenever those things happen, we’ll review genomic tests again.

Burbrink et al. 2019 report with great confidence,
“Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups.

The opposite is true, as we’ve seen before.
Genomics is providing false positive family trees that do not match phenomic trees (Fig. 1)… not all the time, but often enough not to trust deep time genomics.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates. This cladogram includes fossil taxa and documents a gradual accumulation of traits across all taxa. 

Burbrink et al. 2019 report with great confidence,
“Here, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome scale data.

Genomic studies cannot and do not include fossil taxa,
which also puts genomic studies at a great disadvantage. How do you test genomic studies? You test genomic studies with phenomic studies, not the other way around.

Burbrink et al. 2019 report with great confidence,
“We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata.

According to Wikipedia and Variety of Life:
Toxicofera =  proposed clade Serpentes (snakes), Anguimorpha (monitor lizards, gila monster, and alligator lizards) and Iguania (iguanas, agamas, and chameleons). None of this is supported by the LRT.

Scleroglossa = includes anguimorphs, geckos, autarchoglossans (scincomorphs and varanoids), and amphisbaenians. For the most part this is supported by the LRT, but snakes are not listed here and they are related to geckos. Amphisabaenians are scincomorphs.

Macrostomata = non-fossorial snakes. In the LRT (subset Fig. 1) fossorial (= burrowing snakes) are a clade within the non-fossorial snakes. In other words, Burbrink’s team got it backwards, perhaps because no fossil snakes and pre-snakes were included.

“We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; and between the three toxiferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).”

Don’t trust the results recovered by Burbrink et al. 2019. 
Genomic tests in lizards are not supported by validated phenomic tests. Only the LRT (at present) documents a gradual accumulation of traits across extinct and extant lepidosaur and squamate taxa that goes back to jawless Silurian fish.

Sorry guys, no matter how much effort went into creating Burbrink et al. and its supplementary data with 15 co-authors, it turned out not to provide any insights into squamate evolutionary events and therefore, was a waste of time. Worse yet, it promoted false positives as good science.

Next time,
before promoting genomics above phenomics, test genomics against phenomics.  Yesterday we looked at a possible reason why genomic tests do not replicate phenomic tests.


References
Burbrink FT et al. (14 co-authors) 2019. Interrogating genomic-scale data for Squamata (lizards, snakes, and amphisbaenians) shows no support for key traditional morphological relationships. Systematic Biology, syz062 (advance online publication)
doi: https://doi.org/10.1093/sysbio/syz062
https://academic.oup.com/sysbio/advance-article-abstract/doi/10.1093/sysbio/syz062/5573126

Hongshanxi: just barely NOT a squamate

Updated July 7, 2020
the LRT moves Meyasaurus, Indrasaurus and Hoyalacerta to the base of the Yabeinosaurus + Sakurasaurus clade within the Scleroglossa and Squamata.

Dong, Wang, Mou, Zhang and Evans 2019 bring us
Hongshanxi xidi, a tiny, new and rare, complete, articulated and flattened Oxfordian (earliest late) Jurassic lepidosaur the authors had difficulty nesting with both traits and molecules.

In happy contrast,
the large reptile tree (LRT 1578 taxa) recovers Hongshanxi as the proximal outgroup to the clade Squamata, between Liushusaurus (Evans and Wang 2010) Early Cretaceous, ~10 cm) and IguanaEuposaurus cirinensis (Lortet 1892, MHNL 15681, Late Jurassic, Kimmeridgian, 155 mya, 3.5cm snout vent length) without firsthand observations.

Figure 1. Hongshanxi in situ with DGS colors added to pectoral region.

Figure 1. Hongshanxi in situ with DGS colors added to pectoral region.

From the abstract
It [Hongshanxi] is distinguished from other Jurassic-Cretaceous lizards by a unique combination of derived characters, notably a long frontal with posterior processes that clasp the short parietal; cranial osteoderms limited to the lower temporal and supraocular regions; and an elongated manus and pes. Phylogenetic analysis using morphological data alone places the new taxon on the stem of a traditional ‘Scleroglossa’, but when the same data is run with a backbone constraint tree based on molecular data, the new taxon is placed on the stem of Squamata as a whole. Thus its position, and that of other Jurassic and Early Cretaceous taxa, seem to be influenced primarily by the position of Gekkota.”

Figure 2. Hongshanxi skull with DGS colors added.

Figure 2. Hongshanxi skull with DGS colors added.

Unfortunately
Dong et al. were using an outdated and incomplete taxon list, that of Gauthier 2012 (610 characters, 192 taxa) with maybe a dozen additional Early Cretaceous taxa described since then. The authors report, “However, as with many other Jurassic and early Cretaceous taxa (e.g. Scandensia, Yabeinosaurus, Hoyalacerta, Liushusaurus), the phylogenetic position of Hongshanxi n. gen. cannot be clearly resolved.”

That may be because the authors do not understand that a series of lepidosaurs preceded the Squamata. These predecessors include the pterosaur clade, Tritosauria. In the LRT the Lepidosauria is completely resolved with high Bootstrap values at nearly all nodes with the addition of Hongshanxi, which looks quite a lot like its nearly coeval sister taxa and is similar in size and location.

Figure 3. Hongshanxi pelvic region in situ with DGS colors added

Figure 3. Hongshanxi pelvic region in situ with DGS colors added

The authors also do not realize
they cannot rely on molecular studies to clarify relationships in deep time. The solution to these problems is online, the LRT, ready for anyone to use. If workers want to continue ‘spinning their wheels’ recovering no clear solutions, that’s to the detriment of our science.

Oddly
the hands and feet of Hongshanxi are elongate, like their arboreal sisters, but the penultimate phalanges are shorter than the more proximal phalanges, distinct from their arboreal sisters. The torso is short relative to the femur length. The authors correctly note the very odd lack of a straight frontal-parietal suture. Also very odd is the open acetabulum (hip joint), which was overlooked by the authors.


References
Dong L, Wang Y, Mou L, Zhang G and Evans SW 2019. A new Jurassic lizard from China in Steyer J.-S., Augé M. L. & Métais G. (eds), Memorial Jean-Claude Rage: A life of paleo-herpetologist. Geodiversitas 41 (16): 623-641. https://doi.org/10.5252/geodiversitas2019v41a16.

http://geodiversitas.com/41/16

 

Bipedal Cretaceous lizard tracks

These are the oldest lizard tracks in the world…
(if you don’t consider Rotodactylus (Early Triassic) strictly a ‘lizard’ (= squamate). One rotodactylid trackmaker, Cosesaurus, is a tiny lepidosaur).
Figure 1. Bipedal lizard tracks from South Korea in situ.

Figure 1. Bipedal lizard tracks from South Korea in situ. They are tiny.

From the abstract
“Four heteropod lizard trackways discovered in the Hasandong Formation (Aptian-early Albian), South Korea assigned to Sauripes hadongensis, n. ichnogen., n. ichnosp., which represents the oldest lizard tracks in the world. Most tracks are pes tracks that are very small. The pes tracks show “typical” lizard morphology as having curved digit imprints that progressively increase in length from digits I to IV, a smaller digit V that is separated from the other digits by a large interdigital angle. The manus track shows a different morphology from the pes. The predominant pes tracks, the long stride length of pes, narrow trackway width, digitigrade manus and pes prints, and anteriorly oriented long axis of the fourth pedal digit indicate that these trackways were made by lizards running bipedally, suggesting that bipedality was possible early in lizard evolution.”
Actually, the lizard was not running.
Typically in running tracks the prints are very far apart and these tracks are sometimes left toe to right heel.
Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added,

Figure 2. Original and new tracings of the bipedal lizard tracks from South Korea. PILs are added. Manual digit 4 and 5 appear to have shifted.

 The authors did not venture who made the tracks.
They reported, “based on the palaeobiogeographic distribution of facultative extant families, the lizard that produced S. hadongensis tracks could well have been a member of an extinct family or stem members of Iguania, which was present in the Early Cretaceous.”
Actually the closest match among tested taxa
is with Eichstaettisaurus (Fig. 1), a basal member in the lineage of snakes. And this clade is close to the origin of geckos. ReptileEvolutiion.com and the large reptile tree would have been good resources for the authors to use. Lots of lizard pedes were illustrated and scored there.
Figure 3. Originally pictured as a generic lizard (below), here Eichstattsaurus scaled to the track size walks upright.

Figure 3. Originally imagined  as a generic lizard (below), here Eichstattsaurus matched and scaled to the track size walks upright.

 Based on a phylogenetic analysis of the tracks
the closest match in the LRT is with Eichstaettisaurus, so a slightly larger relative made them. Distinct from the skeletal taxon, the trackmaker had a longer p2.1 than 2.1 and pedal digit 1 was quite short. Otherwise a good match in all other regards.
So why walk bipedally?
It was walking, not running, so escape from predation can be ruled out. Elevating the upper torso and head, like a cobra, can be intimidating to rivals, or just offer a better view over local plant life. This sort of flexibility could have helped them get into the trees and then to move to higher branches.
References
Lee H-J, Lee Y-N, Fiorillo AR &  LÃ J-C 2018. Lizards ran bipedally 110 million years ago. Scientific Reports 8: 2617. doi:10.1038/s41598-018-20809-z

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

Chometokadmon is a basal gekko

A few years ago,
Evans et al. 2006 re-introduced us to the Lower Cretaceous lizard, Chometokadmon fitzingeri (MPN 539) from Italy. That genus was originally described by Costa 1864. The Evans team nested Chometokadmon between Dorsetisaurus and Xenousauridae at the base of the Anguimorpha (varanids + helodermatids). Note that Xenosaurus and Heloderma have laterally facing nares, not dorsal nares.

Figure 1. Chometokadmon in situ. Known for over 100 years, this flat skulled gekko had longer toes than typical.

Figure 1. Chometokadmon in situ. Known for over 100 years, this flat skulled gekko had longer toes than typical.

The large reptile tree (LRT) nests Chometokadmon at the base of the geckos, between Tchingisaurus and Gekko smithii. Like geckos, Chometokadmon lacks a postorbital and thus has a confluent orbit + both temporal fenestra. Helodermatids have a similar temporal architecture lacking temporal bars, but do not have a triangular rostrum in dorsal view.

Perhaps
the Evans team made a mistake in identifying a quadrate alone as a quadrate + squamosal (Fig. 2). In most geckos, the quadrate is a tall slender bone, but in the basalmost gecko in the LRT, Tchingisaurus (Fig. 2), the lateral quadrate has an anterior rim that dorsally bends posteriorly, like the purported squamosal in Chometokadmon. No close relatives have a squamosal with the shape proposed by Evans et al. The triangular outline of the skull in dorsal view along with the short teeth are also gekko traits not found in candidates proposed by the Evans team.

FIgue 2. Skull and reconstruction of Chometokdamon by Evans et al. 2006.

FIgue 2. Skull and reconstruction of Chometokdamon by Evans et al. 2006. Note the loss of the postorbital and jugal bars.

A comparison to other geckos
(Fig. 3) makes the case rather clear to Chometokdamon may be one of them. A skull twice as wide as tall plus the confluence of the orbit with the both the upper and lower temporal fenestrae are gecko traits.

Figure 1. Click to enlarge. Tchingisaurus, a basal Gekkotan, according to the large reptile tree.

Figure 3. Tchingisaurus, a basal Gekkotan, according to the large reptile tree.

Figure 3. Gekko smithii is an extant member of a genus that extends to the Early Cretaceous. Note the lack of temporal bars and the forward extension of the supratemporal along the lateral parietal.

Figure 4. Gekko smithii is an extant member of a genus that extends to the Early Cretaceous. Note the lack of temporal bars and the forward extension of the supratemporal along the lateral parietal, as in Chometokadmon.

As a basal gekko
Chometokadmon joins two rather closely related and coeval basal pro-snake genera Ardeosaurus and Eichstattisaurus that we discussed earlier here and were mistakenly  considered basal geckos by Simoes et al. 2016. Their mistake, once again, was taxon exclusion, a problem often solved by the large gamut of taxa in the LRT.

References
Costa OG 1864. Paleontologia del Regno di Napoli, III. Atti dell’Accademia Pontaniana 8, 1e198.
Evans SE, Raia P, Barbera C 2006. The Lower Cretaceous lizard genus Chometokadmon from Italy. Cretaceous Research 27:675-683.
Simões TR, Caldwell MW, Nydam RL and Jiménez-Huidobro P 2016. Osteology, phylogeny, and functional morphology of two Jurassic lizard species and the early evolution of scansoriality in geckoes. Zoological Journal of the Linnean Society (advance online publication) DOI: 10.1111/zoj.12487 http://onlinelibrary.wiley.com/doi/10.1111/zoj.12487/fullwiki/Ardeosaurus

wiki/Chometokadmon

Mid-Cretaceous lizards in amber from Myanmar

A new paper
from Daza et al. (2016) brings us several lizards in amber from the Mid Cretaceous (Fig. 1).

Figure 1. Mid-Cretaceous lizards in amber from Daza et al. 2016. Highlighted specimens are examined here.

Figure 1. Mid-Cretaceous lizards in amber from Daza et al. 2016. Highlighted specimens are examined here.

I was chiefly interested in
the unidentified ones, JZC Bu267 (Fig. 2) and JZC Bu1803 (Fig. 4).

Figure 2. JZC Bu 267 nests with the pre-snake, Jucarseps in the large reptile tree.

Figure 2. JZC Bu 267 nests with the pre-snake, Jucarseps in the large reptile tree.

JZC Bu 267
is a tiny, slender, short-legged, long-toed lizard that nests with the Early Cretaceous pre-snake, Jucarseps, (Bolet and Evans 2012, Fig. 3) in the large reptile tree. This nesting is based on relatively few traits as the skull is largely missing while dermis covers large portions of the post-crania. The two are about the same size and overall proportions.

The authors report, “The preservation of  JZC Bu267 is exceptional; it includes the epidermis and soft tissues and even a unique extended tongue tip with a narrow medial projection that does not resemble the form of any described squamate tongues.” According to Wikipedia, reptiles developed forked tongues in several clades independently.

Figure 1. Jucaraseps in situ. This tiny long lizard is in the lineage of terrestrial snakes.

Figure 3. Jucaraseps in situ. This tiny long lizard is in the lineage of terrestrial snakes and nests as a sister to JZC Bu 267,

So this find
extends the range of the Jucarseps clade from SW Europe to SE Asia.

Figure 4 JZC-Bu1803 has a relatively large skull. This and other traits nest it with the basal scleroglossan, Calanguban in the large reptile tree.

Figure 4 JZC-Bu1803 has a relatively large skull. This and other traits nest it with the basal scleroglossan, Calanguban in the large reptile tree.

JZC Bu1803
(3.2cm snout vent length) Is more thoroughly covered in fine scales. Nevertheless, a large enough list of traits was gleaned from the photo to nest JZC Bu 1803 with the basal scleroglossan, Calanguban (Simoes, Caldwell and Kellner 2014, Early Cretaceous), which is also the same size.

According to Daza et al. “The ventral scales are large, quadrangular, and arranged in regular transverse and longitudinal rows as in most living teiids and lacertids. Remarkable features of this specimen are the extremely long digits and claws.

“A digital endocast of the leftmaxilla exposed the entire tooth row section, a dentition including about 14 functional teeth, and an estimated 19 tooth loci. Tooth attachment is pleurodont and morphology is heterodont, with an abrupt transition from conical and recurved teeth (first 12) to tricuspid (with divided crowns, last 7). Tricuspid (or triconodonot) dentition is widespread among squamates. Among extant groups, the combination of anterior fang-like and posterior tricuspid teeth with parallel margins, where mesial and distal cusps are shorter than the main apex,most closely resembles that of lacertids and teiids.”

Figure 4. Calanguban nests as a sister to JZC Bu 1803 in the large reptile tree.

Figure 5. Calanguban nests as a sister to JZC Bu 1803 in the large reptile tree.

So this find
extends the range of the Calanguban clade from SW Europe across the then narrow Atlantic to NE Brazil.

Figure 6. The two new and unidentified amber embedded specimens nest as squamates that already have names here.

Figure 6. The two new and unidentified amber embedded specimens nest as squamates that already have names here.

The authors indicate
that more data will be forthcoming on these specimens. More can be seen on YouTube here.

References
Bolet A and Evans SE 2012. A tiny lizard (Lepidosauria, Squamata) from the lower Cretaceous of Spain. Palaeontology 55:491-500.
Daza J, Sanley EL, Wagner P, Bauer A and Grimaldi DA 2016. Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards. Science Advances 2(3): e1501080. DOI: 10.1126/sciadv.1501080
Simoes TR, Caldwell MW and Kellner AWA 2014.
 A new Early Cretaceous lizard species from Brazil, and the phylogenetic postion of the oldest known South American squamates. Journal of Systematic Palaeontology. http://dx.doi.org/10.1080/14772019.2014.947342

YouTube with rotating scans