Gliding Lizard Diversity and Data – This You Gotta See!

Just a quick hit to alert you to a fascinating blog page on gliding lizards.

Figure 1. Gliding lizard Draco volans with ribs extended.

Figure 1. Gliding lizard Draco volans with ribs extended. Click to see more.

Dozens of photos. Lots of background and cool information.

You can find it here.

More on prehistoric gliding lepidosauriforms (not squamates, not lepidosaurs) here and here. Earlier we talked about the evolution of this “rib” gliders here.

DGS – Digital Graphic Segregation helps reconstruct the Dauhugou lizard – again

Earlier we looked at the unnamed Daohugou lizard, IVPP V1347. Today there’s an update.

Figure 1. The skull of the Daohugou lizard IVPP V1347. At left, in situ. Middle as traced using DGS methods. At right, as figured by Evans and Wang 2005.

Figure 1. Click to enlarge. The skull of the Daohugou lizard IVPP V1347. At left, in situ. Middle as recently traced using DGS methods. At right, as figured by Evans and Wang 2005. Epipterygoids in yellow. Pterygoids in purple.

In phylogenetic analysis it nested as a sister to the basal tritosaur, Lacertulus, but the Daohugou lizard lived much later. The Daohugou lizard also nested with other Early Cretaceous tritosaur lizards, MeyasaurusHuehuecuetzpalli and Tijubina. These were difficult for professional paleontologists, like Evans and Wang (2005), to nest within the Iguania and Scleroglossa. That’s because they nest elswhere, in the Tritosauria!

Here the skull of the still unnamed Daohugou lizard is revised from an earlier reconstruction attempt. Here more details emerge with the mandible, naris, palatal and temporal regions. With these many minor modifications the phylogenetic nesting did not change.

Figure 2. The Daohugou lizard reconstucted. It's closest known relative is the basal tritosaur lepidosaur, Lacertulus.

Figure 2. The Daohugou lizard reconstucted. It’s closest known relative is the basal tritosaur lepidosaur, Lacertulus, but it phylogenetically leads to Huehuecuetzpalli.

Found and reconstructed in this round of DGS:
Epipterygoids, palate elements, a longer naris (shorter maxilla), more teeth below the orbit, lateral processes for the posterior frontal and anterior parietal, squamosal, anterior mandible elements, lacrimal.

In the lineage of pterosaurs
And because this Daohugou lizard nests within the Tritosauria, it is a sister to a similar-looking but currently unknown ancestor to pterosaurs that probably existed side-by-side with Lacertulus in the Late Permian.

References
Evans SE and Wang Y 2009. A long-limbed lizard from the Upper Jurassic/Lower Cretaceous of Daohugou, Ningcheng, Nei Mongol, China. Vertebrata PalAsiatica 47: 21–34.

New Early Permian(!) iguanid lizard found vulcanized!

This page was again modified March 17, 2018 to reflect an new nesting for Ascendonanus as a basal iguanid. 

Rößler et al. (2012) just published an account of an Early Permian ecosystem preserved by explosive volcanism. Among the illustrated creatures was a single, reptile (Fig. 1, TA1045, now Ascendonanus) approximately 14 cm snout to vent. Despite its apparent similarity to an iguanid, it was not immediately apparent what sort of reptile this was to Rößler et al. TA 1045 was included in the large reptile tree and it indeed nested with basal iguanids.

Figure 1. Click to enlarge. The Early Permian reptile (TA1045) preserved in volcanic debris, from Roßler et al. 2012. Yes, those are transverse belly scales beneath the ribs.It looks like the complete rostrum was preserved, right to the edge of the matrix. This image is considered low in resolution. More details can be gleaned with better images.

Figure 1. Click to enlarge. This low-rez image was used in 2012 to create these images. See figure 2 for an update. The Early Permian reptile (TA1045) preserved in volcanic debris, from Roßler et al. 2012. Yes, those are transverse belly scales beneath the ribs.It looks like the complete rostrum was preserved, right to the edge of the matrix. This image is considered low in resolution. More details can be gleaned with better images.

Phylogenetic analysis
Using DGS to tease out the details, then adding this taxon to the large reptile tree nests TA1045 as a sister to Liushusaurus an extinct iguanid. And that makes Ascendonanus the oldest known squamate.

Figure 1. The skull of Ascendonanus has a diapsid temporal configuration with clearly visible upper temporal fenestra and a typical iguanid skull morphology.

Figure 1. The skull of Ascendonanus has a diapsid temporal configuration with clearly visible upper temporal fenestra and a typical iguanid skull morphology.

Soft tissue
Flesh and a complete series of belly scales wider than the ribcage make the vulcanized reptile even more interesting, despite the lack of good preservation of the feet and hands.

Chronology – This is Where it Gets REALLY Exciting!!
TA1045 pushes the fossilized origins of the lepidosauriformes way back to the early part of the Early Permian (290 mya), within 10 million years of the Carboniferous (Pennsylvannian). That means more primitive lepidosaurs deep into the Pennsylvannian. There must have been an explosive radiation of new lepidosauromorphs at that time, currently unknown as fossils.

References
Rößler R, Zierold T, Feng F, Kretzschmar R, Merbitz M, Annacker V and Schneider JW 2012. A snapshot of an Early Permian ecosystem preserved by explosive volcanism: new results from the Chemnitz Petrified Forest, Germany.PALAIOS 27(11):814-834. pdf online.

Huehuecuetzpalli in the eyes of Gauthier et al. 2012

Huehuecuetzpalli mixtecus (Reynoso 1998, Early Cretaceous, Middle to Late Albian, Fig. 1) is very primitive lepidosaur known from two closely associated specimens, one a juvenile, the other an adult. Huehuecuetzpalli has taken center stage here (at PterosaurHeresies) and at ReptileEvolution.com as a basal member of the Tritosauria. This third clade of squamates includes an odd assortment of drepanosaurs, tanystropheids and fenestrasaurs including pterosaurs that have been completely ignored and overlooked in all professional lizard studies.

Huehuecuetzpalli

Figure 1. The father of all pterosaurs and drepanosaurs, Huehuecuetzpalli, a basal lepidosaur.

A recent paper by Gauthier et al. (2012) considered Huehuecuetzpalli among the many lizards in its tree. A few quotes from that paper are worthy of attention. They nested Huehuecuetzpalli  alone between sphenodontids, like Gephyrosaurus and Sphenodon, and the Squamata (all other known lizards, divided by the Iguania and Scleroglossa (including snakes)).

Unfortunately Gauthier et al. (2012) did not reference the large reptile tree (or create their own more expansive tree of lizards) so they completely overlooked the tritosaurs as descendants of a sister to Huehuecuetzpalli. It should not have nested all alone. There was an opportunity missed that became yet another case of taxon exclusion. Below I make comments (in hot pink) on the small section of Gauthier (2012) regarding Huehuecuetzpalli.

Annotated Notes from Gauthier et al. (2012):

“Stem squamata – Given the antiquity of the squamate stem—which must extend deep into the Triassic (1)—surprisingly few stem fossils can be referred with any confidence to that great branch of the lepidosaur tree (2). Huehuecuetzpalli mixtecus, from the Early Cretaceous of Mexico, seems to be one of these (Reynoso 1998). This species is reasonably well known by the standards of Mesozoic lizard paleontology, as it is represented by two fairly complete skeletons, with some patches of skin impressions, of juvenile and nearly adult individuals. H. mixtecus apparently represents an entirely extinct side branch off the squamate stem (3). All major living clades of lizards— Iguania, Gekkota, Scincomorpha and Anguimorpha—diverged by the Late Jurassic (Estes 1983; Conrad 2008 (4)). Albian-age H. mixtecus must therefore have been separated from the surviving branch of the lizard tree by anywhere from 25 to 50 million years (5). Unsurprisingly, it displays several distinctive autapomorphies (see Appendix 4).

“Huehuecuetzpalli mixtecus is joined to the lizard crown by 20 unambiguous squamate synapomorphies (100% BP, 100% PP, 16 BS; see Appendix 4). Three of those are unique and unreversed on our tree: 177(1), 181(1) and 295(1). Among these diagnostic characters are many of those involved in the kinetic masticatory system unique to lizards (6). H. mixtecus is, however, also quite primitive in many ways; for example, skin impressions indicate that it retained a mid-dorsal row of spiny scales (7), a feature diagnostic of lepidosaurs that is retained today only among iguanian lizards and Sphenodon punctatus (scleroglossans generally lack the mid-dorsal scale row originally present in Reptilia; Gauthier, Kluge and Rowe 1988). The upper temporal arch of H. mixtecus displays a mixture of ancestral and derived traits; the postorbital, for example, still fits into a V-shaped recess on the lateral face of the squamosal as in diapsids ancestrally (8); Its squamosal is nevertheless distinctly lizard-like in having a peg at its posterior tip, on which pivots the mobile (streptostylic) quadrate uniquely diagnostic of crown lizards (Robinson 1967).(9)

“Crown Squamata – Huehuecuetzpalli mixtecus shares a few apomorphies characteristic of (at least some) iguanians, such as fused hourglass-shaped frontal bones and a small subtriangular postfrontal bone confined to the orbital rim (Reynoso 1998) (10). Nonetheless, it seems to lie well outside the lizard crown, because it lacks—so far as it is preserved—the 13 unambiguous synapomorphies that diagnose Squamata. … In any case, this morphological “long branch” simultaneously underscores our confidence in squamate monophyly while highlighting just how little we know about their evolutionary origins.(11)


Notes: (1) Actually the antiquity of the non-sphenodontid lepidosaurs extends back at least to Lacertulus of the Early Permian with more primitive taxa, like Homoeosaurus, and Dalinghosaurus (both ignored by Gauthier et al. 2012) surviving into later ages (Late Jurassic and Early Cretaceous respectively).”

(2) Listed above and look for others here.

(3) Indeed!

(4)  We can be confident of a much earlier Late Permian date for the tritosaur/squamate split due to the preponderance of fenestrasaur tracks in the Early Triassic (Peabody 1948).

(5) Add at least the entire Triassic to this number.

(6) This is reversed in some, but not all tritosaurs, principally by the shortening of the lateral temporal fenestra and the redevelopment of a quadratojugal with a loose connection to the quadrate.

(7) This dorsal series finds the acme of its expression in Longisquama.

(8) The Diapsida that Gauthier et al. 2012 is thinking of is diphyletic.

(9) See (6).

(10) As in tanystropheids and fenestrasaurs including pterosaurs.

(11) With the large reptile tree we actually know a very good set of sample ancestral taxa back to Ichthyostega (and we know its ancestors, so…, the list really extends as far back as you care to look.)


Besides the Tritosauria, Gauthier et al. (2012) excluded several fossil lepidosaurs that were key to understanding relationships in the large reptile tree. Without these their tree suffers by comparison despite its size. Taxon exclusion needs to become a thing of the past. Professional studies have suffered long enough.

 

References
Gauthier JA, Kearney M, Maisano JA, Rieppel O and Behlke ADB 2012. Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record. Bulletin of the Peabody Museum of Natural History 53(1):3–308.
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Reynoso V-H 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodríguez, Central México. Philosophical Transactions of the Royal Society, London B 353:477-500.

The reptile DNA problem: maybe this is the answer…

Q: How do you arrive at a family tree of reptiles?
1.
You can look at hundreds of taxa and score them for hundreds of characters and let maximum parsimony recover the family tree, as I did here. This is following in the paths of dozens of others who have created their own subsets of the reptile family tree with their own taxon and character lists. Because morphology is an expression of genetics, morphology is really the only genetics that counts. Morphology helps you survive in your niche and enhances secondary sexual characteristics to help you get laid to create replicants of your own naturally selected self.

or

2. You can look at the molecular DNA of several distinct specimens (all currently living) and let maximum parsimony recover a much more unfocused family tree leaving out hundreds of extinct taxa with no known living counterparts. Of course some of this DNA doesn’t express anything. Some of it jumps around the chromosomes. And DNA cannot be recovered from the vast majority of extinct taxa, so we’re left with huge ghost lineages, during which “things” happen (see below). Even the sex chromosomes are different between birds, mammals and lizards.

Male mammals have the XY combination while females have XX. Male birds carry what’s known as the ZZ pair and females have the ZW pair. The green anole X chromosome is a microchromosome. Yes, it’s nothing compared to having a skull, tail, four feet, five toes and relative constants like those when it comes to DNA.

BTW I freely admit to not knowing much about molecular studies except that they sometimes don’t replicate morph studies.

The DNA problems don’t end there…
We’re talking about reptiles here: DNA study results do not replicate morphological study results. Often DNA study results do not replicate other DNA study results. DNA is changing even when morphology does not (Hays 2008). This alone could be the reason for the discrepancy in DNA and morphology among reptiles (and not among mammals and humans involved in paternity suits).

Is this why reptile DNA studies don’t match morph studies?
A recent article on genetic sequencing of an anole lizard DNA reports, “We’ve now sequenced a lizard genome for the first time ever. The anoles shed light on non-coding sequences of genes. What they might be are the husks of special DNA sequences known as transposons. These can only be described as “jumping DNA”, able to actually move through the genomes and copy and paste themselves elsewhere. Transposons can give any genome that carries them great agility and resilience in dealing with unexpected environmental challenges.”

Lizard egg proteins
From the same article, “It appears that, as far as egg genes are concerned, reptiles are in a constant state of evolutionary flux, with the proteins revealing clear signs of rapid evolutionary change.”

The dorsal spines of Tuatara (Sphenodon).

Figure 1. The Tuatara (Sphenodon)

The Hays et al. 2008 abstract
“The tuatara of New Zealand is a unique reptile that coexisted with dinosaurs and has changed little morphologically from its Cretaceous relatives. Tuatara have very slow metabolic and growth rates, long generation times and slow rates of reproduction. This suggests that the species is likely to exhibit a very slow rate of molecular evolution. Our analysis of ancient and modern tuatara DNA shows that, surprisingly, tuatara have the highest rate of molecular change recorded in vertebrates. Our work also suggests that rates of neutral molecular and phenotypic evolution are decoupled.”

I take this to mean DNA genetic evolution is decoupled from morphological genetic evolution in the Lepidosauria (but not necessarily decoupled in other living things). With that hanging over our collective decision making processes, maybe morphological genetic studies should trump DNA genetic studies in non-mammalian reptiles.

Reptile DNA studies might be interesting, but let’s not hang our hats on them. Let’s stick with fossils and phylogenetic analysis. That covers all the bases down to the specimen.

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
Hay JM, Subramanian S, Millar CD and Mohandesan E 2008. Rapid molecular evolution in a living fossil. Trends in Genetics, 24(3):106-109.

The Origin of the Amphisbaenia

Updated August 12, 2014. Moving Cryptolacerta to a closer relationship to Heloderma, elevating Sineoamphisbaena to its place between skinks and amphisbaenids.

Amphisbaena literally means, “goes both ways.” The name is that of the mythological “Mother of Ants,” an ant-eating serpent with a head on both ends. Amphisbaena is also a genus within the Amphisbaenia. Like its mythological namesake, Amphisbaena can back up as easily as it moves forward, despite having no legs.

Amphisbaenia are the worm lizards, typically (with one exception, Figure 1) legless squamates that burrow and have a superficial resemblance to earth worms, including having their scales arranged in rings (annuli). Their right lung is reduced to make more room for the left lung. (In snakes the left lung is reduced.) The eyes are reduced and deeply recessed and the tail resembles the head. Amphisbaenians are so different from other squamates that they have been considered a third suborder, after lizards and snakes.

The primitive Amphisbaenian, Bipes.

Figure 1. The primitive amphisbaenian, Bipes.

Bipes, a Primitive Extant Amphisbaenian
Bipes (Figure 1) is a living amphisbaenian with strong front legs. The hand is stout, like that of a mole, with digits 2 and 3 the longest, digit 1 absent and digit 5 vestigial. The vestigial hind limbs do extend beyond the body wall. By contrast, in typical lizards digit 4 is the longest.

Extinct Burrowers
Several fossil taxa have been linked to amphisbaenians. Tamaulipasaurus lived during the Early Jurassic. Sineoamphisbaena and Crythiosaurus lived during the Late Cretaceous.  Spathorhynchus lived during the early Oligocene. Most of these are known from skulls and partial skulls. No hands yet known in any of these taxa.

Amphisbaenian Origins – part 1 – Sineoamphisbaena
Wu et al. (1993), Wu et al. (1996) and Gao (1997) proposed and argued that a round-skulled Late Cretaceous squamate, Sineoamphisbaenea (Figure 2), was the oldest known amphisbaenian. Unfortunately, it didn’t look very much like most amphisbaenians (Figure 2) which made accurate nesting something of a problem in the eyes of many.

Amphisbaenian Origins – part 2 – Not Sineoamphisbaena
Kearney (2003) argued that Sineoamphisbaena nested closer to Macrocephalosaurus and that Amphisbaena nested with Dibamus and snakes, not far from Gekko and the legless geckos, the Pygopodidiae.

 

Figure 2. Cryptolacerta and kin, including Heloderma and the Amphisbaenia.

Figure 2. Cryptolacerta and kin, including Heloderma and the Amphisbaenia.

Amphisbaenian Origins – part 3 – Cryptolacerta
Müller et al. (2011) argued that a new Eocene lizard, Cryptolacerta  (Figure 2), was the sister to the Amphisbaenia and both were sisters to Sineoamphisbaena and the Teiioidea, a lizard taxon that includes the skinks, Gymnophthalmus and Chalcides. 

Where Do Amphisbaenians Nest in the Large Study?
Here Cryptolacerta does indeed nest close to skinks and amphisbaenians, but it nests closer to Heloderma, another burrowing lizard. Müller et al. (2011) reported that Cryptolacerta had sealed up its upper temporal fenestrae with expansion of the very large postfrontal bone. I was unable to duplicate that reconstruction. Instead I found upper temporal fenestrae in the specimen. A GIF movie and comparative reconstructions can be found here. In any case, amphisbaenians do not add bone to their skulls, they lose bone.

Amphisbaenians nest close to skinks with Sineoamphisbaena nesting close to the base of the other amphisbaenians. In consideration of Kearney (2003), I deleted all amphisbaenians, then all skinks and amphisbaenians from the large study, but those tests failed to dislodge Sineoamphisabaenia form its node, which kept it far from Macrocephalosaurus.

Summary
While amphisbaenians are distinct from most other lizards, they are closer to skinks and legless skinks than to any other lizard taxa. More legless taxa will be added to the large tree as time goes by and I will report on each one in turn.

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:
Cope ED 1894. On the genera and species of Euchirotidae. American Naturalist 28: 436-437.
Gao K 1997.
 
Sineoamphisbaena phylogenetic relationships discussed. Canadian Journal of Earth Sciences. 34: 886-889. online article
Kearney M 2003. The Phylogenetic Position of Sineoamphibaena hextabularis reexamined. Journal of Vertebrate Paleontology 23 (2), 394-403.
Müller J, Hipsley CA, Head JJ, Kardjilov N, Hilger A, Wuttke M and Reisz RR 2011. Eocene lizard from Germany reveals amphisbaenian origins. Nature 473 (7347): 364–367. doi:10.1038/nature09919
Wu XC., Brinkman DB, Russell AP, Dong Z, Currie PJ, Hou L, and Cui G 1993. Oldest known amphisbaenian from the Upper Cretaceous of Chinese Inner Mongolia. Nature (London), 366: 57 – 59.
Wu X-C Brinkman DB and Russell AP 1996. Sineoamphisbaena hexatabularis, an amphisbaenian (Diapsida: Squamata) from the Upper Cretaceous redbeds at Bayan Mandahu (Inner Mongolia, People’s Republic of China), and comments on the phylogenetic relationships of the Amphisbaenia. Canadian Journal of Earth Sciences, 33: 541-577.
Papenfuss TJ 1982. The Ecology and Systematics of the Amphisbaenian Genus Bipes. Occasional papers of the California Academy of Science 136: 1-42.

wiki/Cryptolacerta
wiki/Amphisbaenia
wiki/Bipes
wiki/Sineoamphisbaena