Portunatasaurus almost enters the LRT with dolichosaurs, not mosasaurs

Too few traits are present
for Portunatasaurus (Figs. 1–3) to be entered into the LRT without loss of resolution, but that shouldn’t stop us from figuring out what it is and what it isn’t.

Figure 1. Portunatasaurus compared to stem mosasaur, Aigialosaurus and to marine stem snake, Aphanizocnemus.

Figure 1. Portunatasaurus compared to stem mosasaur, Aigialosaurus and to marine stem snake, Aphanizocnemus.

From the Mekarski et al. 2019 abstract:
“A new genus and species of plesiopedal mosasauroid, Portunatasaurus krambergeri, from the Cenomanian–Turonian (Late Cretaceous) of Croatia is described.”

Ooops. Taxon exclusion rears its ugly head again. In the large reptile tree (LRT, 1823+ taxa) Portunatasaurus (Fig. 1) is closer to aquatic snake ancestors, like Aphanizocnemus (Fig. 1), than a “plesiopedal mosasaurid.” Even with so few traits to test, moving Portunatasaurus closer to mosasaurs and aigialosaurs adds 4 steps. In the LRT Aphanizocnemus nests as a snake ancestor: a marine varanoid dolichosaur scleroglossan squamate.

Figure 2. Portunatasaurus diagram with corrections.

Figure 2. Portunatasaurus diagram with corrections. Note the robust ribs, as in dolichosaurs. Mosasaurs and aigialosaurs have gracile ribs, a trait not tested in the LRT.

Mekarski et al. 2019 continue:
“An articulated skeleton, representing an animal roughly a meter long was found in 2008 on the island of Dugi Otok. The specimen is well represented from the anterior cervical series to the pelvis.”

There is no lumbar area in the Mekarsi et al. diagram (Fig. 2). Moving the pelvic area posteriorly to give Portunatasaurus a lumbar area agrees with other clade members. Note the robust ribs in Portunatasaurus, as in dolichosaurs. Mosasaurs and aigialosaurs (Fig. 1) have gracile ribs, a trait not tested in the LRT.

Figure 3. Portunatasaurus manus (right) and reconstructed with PILs (left).

Figure 3. Portunatasaurus manus (right) and reconstructed with PILs (left).

Mekarski et al. 2019 continue:
“Preserved elements include cervical and dorsal vertebrae, rib fragments, pelvic fragments, and an exquisitely preserved right forelimb. The taxon possesses plesiomorphic characters such as terrestrial limbs and an elongate body similar to that of basal mosasauroids such as Aigialosaurus or Komensaurus, but also shares derived characteristics with mosasaurine mosasaurids such as Mosasaurus.”

Note: the authors appear to have omitted dolichosaurs from consideration. Dolichosaurs are not mentioned in the abstract. Let me know if this is an error. I have contacted Mekarski for a PDF.

“The articulated hand exhibits a unique anatomy that appears to be transitional in form between the terrestrially capable aigialosaurs and fully aquatic mosasaurines, including 10 ossified carpal elements (as in aigialosaurs), intermediately reduced pro- and epipodials, and a broad, flattened first metacarpal (as in mosasaurines).

Note: the authors appear to be not looking at dolichosaurs. Whenever an author uses the word “unique” it is a good bet that pertinent taxa have been omitted because nothing in “unique” in evolution. What is unique for one clade is commonplace in another.

“The new and unique limb anatomy contributes to a revised scenario of mosasauroid paddle evolution, whereby the abbreviation of the forelimb and the hydrofoil shape of the paddle evolves either earlier in the mosasaur lineage than previously thought or more times than previously considered.”

Authors rarely consider the number one problem in paleontology: taxon exclusion. They prefer those headline-grabbing words like “unique” so they can postulate newer hypotheses ‘than previously considered.” Well, don’t we all… but these authors/PhDs are paid to do this and not make mistakes in taxon exclusion that an amateur with an online cladogram can pick apart without actually seeing the specimen.

“The presence of this new genus, the third and geologically youngest species of aigialosaur from Croatia, suggests an unrealized diversity and ecological importance of this family within the shallow, Late Cretaceous Tethys Sea.”

I assume it is a coincidence that mosasaur ancestors and unrelated snake ancestors were both found in the earliest Late Cretaceous strata surrounding today’s Mediterranean Sea. Let me know of Mekarski et al. tested dolicohosaurs in their cladogram. I had access only to the abstract and some figures.

The paper [PDF] just arrived.
No phylogenetic analysis is provided. Aphanizocnemus is not mentioned. Other dolichosaurs are compared.


References
Mekarski MC et al. 2019. Description of a new basal mosasauroid from the Late Cretaceous of Croatia, with comments on the evolution of the mosasauroid forelimb. Journal of Vertebrate Paleontology. 39: e1577872. doi:10.1080/02724634.2019.1577872.

wiki/Portunatasaurus

The base of the new Lepidosauriformes illustrated to scale

Short one today, 
told mostly in pictures (Figs. 1, 2). Click here or see below for more data and taxon links.

These are the taxa from which all later lepidosaurs
arose and diversified. Thus, these are the ancestors of snakes, pterosaurs, ‘rib’ gliders and rhynchosaurs at their genesis and basal diversification.

Proximal outgroups
in the large reptile tree (subset Fig. 2) include Owenetta, Barasaurus and other small, low, wide owenettid lepidosauromorphs lacking an upper temporal fenestra.

Figure 1. Taxa at the base of the Lepidosauria include Paliguana, Tridentinosaurus, Lanthanolania, Lacertulus, Gephyrosaurus, Megachirella, Lacertulus and Palaegama.

Figure 1. Taxa at the base of the Lepidosauria include Paliguana, Tridentinosaurus, Lanthanolania, Lacertulus, Gephyrosaurus, Megachirella, Lacertulus and Palaegama. See figure 2 for a subset of the LRT.

Basal lepidosauriformes are rare.
For tens of millions of years, between the the first and last days of the Triassic, these are just about all we have in the sparse fossil record at the genesis of new Lepidosauriformes (= Paliguana + Sophineta, their last common ancestor and all descendants). Paliguana is a late survivor of that earlier genesis.

Figure 2. Subset of the LRT focusing on basal Lepidosauria. Taxa in colored blocks are shown to scale in figure 1.

Figure 2. Subset of the LRT focusing on basal Lepidosauria. Taxa in colored blocks are shown to scale in figure 1. Note: the chronology is not reflected in the phylogeny due to the rarity of fossil specimens.

Chronology does not always mirror phylogeny.
And that’s okay.

For instance:
It’s okay that Archaeopteryx was found in Late Jurassic strata and one of its its putative ancestor, Velociraptor, was found in Late Cretaceous strata. You might remember when a bunch of paleontologists waved their hands over that matter, then later blushed and said, “Never mind.” In like manner, it’s okay that Paliguana was found in younger strata than its phylogenetic descendants.


References
http://reptileevolution.com/owenetta.htm
http://reptileevolution.com/paliguana.htm
http://reptileevolution.com/lacertulus.htm

SVP abstract 20: Squamate variability within a single species

Petermann and Gauthier 2020 bring us their views on the 
“potential consequences of our inability to assess intraspecific variability in growth rates.”

From the Petermann and Gauthier abstract:
“An investigation of life-history parameters in the extant iguanian lizard Sauromalus ater (the Common Chuckwalla), a sexually dimorphic species from the SW U.S.A., revealed remarkable intraspecific variability.”

“We found expected differences in growth strategies between males and females, but also within each sex, relating to body size and the timing of sexual maturity. Males and females can grow rapidly to size-at-sexual-maturity, producing above-average adult body sizes. Or, they can grow slowly to size-at-sexual-maturity, yielding adults at or below average body sizes. Neither growth strategy influences longevity. As a result, we found that body size of similar-aged individuals varied by 53% for males and 38% for females, and maximum differences in ‘adults’ of 64% for males and 38% for females.”

Further ranging results were found here earlier in the large pterosaur tree (LPT, 251 taxa) for the lepidosaur pterosaurs, Pteranodon (Fig. 1) and Rhamphorhynchus (Fig. 2). These both became fully resolved in phylogenetic analysis.

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.

Continuing from the Petermann and Gauthier abstract:
“Our results add to previous reports of intraspecific variability in extant and extinct vertebrates. High levels of intraspecific size-variability have multiple implications for vertebrate paleontology.

  1. Morphologically similar specimens from the same locality could belong to the same species even if the size difference among adult individuals exceeds 50%, which is a higher level than previously thought.
  2. Specimens that have been analyzed skeletochronologically and have been found to be similar or identical in chronological age, may not exhibit similar sizes.
  3. Variability in growth strategies may lead to mistaking males and females (especially among sexual dimorphs), or individuals using different growth strategies, as belonging to separate species.”

This is the way evolution works in all vertebrate communities, including humans, where some are taller, some are robust, some are more colorful or sexier, some are brilliant, distinct from the others. In both Rhamphorhynchus and Pteranodon, no two specimens are alike.

“We previously presented evidence that a sequence of sub-terminal skeletal suture fusions relates to maximum body size in squamates, and not to chronological age. This indicates that late-ontogenetic, suture-fusion events could be used to evaluate whether two or more specimens of similar morphology and chronological age are differently-sized conspecifics. Likewise, skeletal suture fusions may aid discerning different growth strategies within a single species, as opposed to the presence of two morphologically similar, but nonetheless separate, species in a single taphonomic assemblage.”

This follows the work of Maisano 2002, who found fusion patterns were phylogenetic in lepidosaurs. a pattern continued in pterosaurs, where fusion patterns are also phylogenetic, distinct form archosaur growth patterns.


References
Maisano JA 2002. 
Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Petermann H and Gauthier JA 2020. Intrespecific variability in an extant squamate and its implications for use in skeletochronology in extinct vertebrates. SVP abstracts 2020.

 

The three-eyed lizard enters the LRT alongside the monkey lizard

The extant, omnivorous Madagascar sand lizard,
Chalarodon madagascariensis (Peters 1854; 22cm long; Figs. 1, 2), enters the large reptile tree (LRT, 1747+ taxa) today. No surprises here. It nests with iguanid squamates between Eocene Koidosaurus and extant Pristidactylus + Basiliscus.

Figure 1. The three-eyed lizard, Chalarodon, in vivo.

Figure 1. The three-eyed lizard, Chalarodon, in vivo.

Figure 2. Chalarodon skull in 5 views. Images from Digimorph.org and used with permission.

Figure 2. Chalarodon skull in 5 views. Images from Digimorph.org and used with permission. Colors added. Note the tiny postfrontal, a vestige fused to the frontal.

The extant bush anole or monkey lizard
Polychrus marmoratus (Linneaus 1758, Figs. 3, 4) also enters the LRT, alongside Chalarodon. This arboreal jungle lizard has a very long prehensile tail and eyes that rotate independently.

Figure 3. The monkey lizard, Polychrus, in vivo.

Figure 3. The monkey lizard, Polychrus, in vivo.

Figure 3. Polychrus marmoratus skull in 4 views from Digimorph.org and used with permission. Colors added.

Figure 4. Polychrus marmoratus skull in 4 views from Digimorph.org and used with permission. Colors added.

References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Peters WCH 1854. Diagnosen neuer Batrachier, welche zusammen mit der früher (24. Juli und 17. August) gegebenen Übersicht der Schlangen und Eidechsen mitgetheilt werden. Ber. Bekanntmach. Geeignet. Verhandl. Königl.-Preuss. Akad. Wiss. Berlin 1854: 614-628.

wiki/Chalarodon_madagascariensis
wiki/Polychrus

Kopidosaurus: no longer an enigmatic iguanian

Scarpetta 2020 bring us a tiny new Eocene lizard,
Kopidosaurus perplexus (YPM VP 8287) known from most of a disarticulated skull still in the matrix, but carefully presented in several views as µCT scans (Fig. 1).

Scarpetta warns his readers,
“Fossil identifications made in a phylogenetic framework are beholden to specific tree hypotheses. Without phylogenetic consensus, the systematic provenance of any given fossil can be volatile. Pleurodonta (Squamata: Iguania) is an ancient and frequently-studied lizard clade for which phylogenetic resolution is notoriously elusive.

Scarpetta reports,
“I address the effects of three molecular scaffolds on the systematic diagnosis of that fossil. I use two phylogenetic matrices, and both parsimony and Bayesian methods to validate my results, and perform Bayesian hypothesis testing to evaluate support for two alternative hypotheses of the phylogenetic relationships of the new taxon.”

Scarpetta did not provide a reconstruction of the skull. That is remedied here (Fig. 1).

Unfortunately Scarpetta’s three molecular scaffolds are based on genes, so they are completely useless for deep time studies, as documented several times in vertebrates. None of the three genomic studies in Scarpetta 2020 agree with each other. None agree with the LRT (Fig. 2).

Unfortunately Scarpetta’s phylogenetic analyses result in lists of suprageneric taxa, not genera, as in the LRT. Scarpetta reports, “The uncertainty of the relationships of Kopidosaurus is due in part to the mosaic morphology of the fossil and the problematic nature of pleurodontan phylogeny.”

There is no such thing as mosaic evolution. So stop using that excuse.

It doesn’t have to be this complicated. Use the LRT. It’s simple. Just Plug ‘n’ Play.

Figure 1. Kopidosaurus perplexus in situ and µCT scans from Scarpetta 2020. Reconstruction added here.

Figure 1. Kopidosaurus perplexus in situ and µCT scans from Scarpetta 2020. Reconstructions in lateral and palatal views added here.

Scarpetta reports,
“YPM VP 8287 preserves no morphological feature or combination of features that would allow clear referral to any member of Pleurodonta.” And that’s why he shouldn’t be “Pulling a Larry Martin” (relying on key traits that might converge). Instead: drop the new taxon into a comprehensive cladogram, like the LRT (Fig. 2), and let the software nest the enigma.

Definition according to Wikipedia:
Pleurodonta (from Greek lateral teeth, in reference to the position of the teeth on the jaw) is one of the two subdivisions of Iguania, the other being Acrodonta (teeth on the top [of the jaw]). Pleurodonta includes all families previously split from Iguanidae sensu lato (CorytophanidaeCrotaphytidaeHoplocercidaeOpluridaePolychrotidae, etc.), whereas Acrodonta includes Agamidae and Chamaeleonidae.”

The frontal and parietal are incomplete
and the skull is small at <2cm. Am I the first to wonder if this was a juvenile skull? Scarpetta does not bring up the subject. The large orbit relative to skull length supports that hypothesis. Otherwise this could be an adult in the process of phylogenetic miniaturization, common at the genesis of many clades (Fig. 2).

Scarpetta concluded,
“Given the phylogenetic volatility of Kopidosaurus, I refrain from favoring any biogeographic or divergence hypothesis based on the identification of the fossil and advise similar caution for other systematically enigmatic fossils, lizard or otherwise.”

Don’t give up! Use the LRT.

Here 
in the large reptile tree (LRT, 1740+ taxa) Eocene Kopidosaurus nests at the base of a clade of living iguanians (Fig. 2). It is a plesiomorphic taxon, but that doesn’t matter to the LRT. Only a suite of characters is able to nest Kopidosaurus with this level of confidence by minimizing taxon exclusion.

Figure 2. Subset of the LRT focusing on basal Squamata. Here Kopidosaurus nests at the base of a clade of living iguanians including Pristidactylus and Anolis.

Figure 2. Subset of the LRT focusing on basal Squamata. Here Kopidosaurus nests at the base of a clade of living iguanians including Pristidactylus, Basisliscus and Anolis.

As a reminder,
the LRT is still using just 238 traits, most of which were not used here due to the lack of a premaxilla, vomer and post-crania. Paleontologists still don’t want to accept the fact that the LRT continues to lump and separate with so few multi-state characters. Even those taxa previously tested without resolution, as described by Scarpetta 2020.


References
Scarpetta SG 2020. Effects of phylogenetic uncertainty on fossil identification illustrated
by a new and enigmatic Eocene iguanian. Nature.com/scientifcreports 10:15734.
https://doi.org/10.1038/s41598-020-72509-2

Lepidosaurian epipterygoids in basal pterosaurs

In 1998 lepidosaurian epipterygoids
were found in the basal lepidosaur tritosaur, Huehuecuetzpalli (Fig. 1, Reynoso 1998; slender magenta bones inside the cheek area).

Figure 2. Huehuecuetzpalli has a tall, narrow epipterygoid, as in other lepidosaurs, and just a pore of an antorbital fenestra in the maxilla.

Figure 1. Huehuecuetzpalli has a tall, narrow epipterygoid, as in other lepidosaurs, and just a pore of an antorbital fenestra in the maxilla.

About two years ago
previously overlooked lepidosaurian epipterygoids were identified here in a more derived lepiodaur tritosaur, Macrocnmeus (Fig. 2, slender green bones in the orbit area) for the first time.

Figure 1. Macrocnemus fuyuanensis (GMPKU-P-3001) in situ and as traced by the original authors, (middle) flipped with colors applied to bones, and (above) bone colors moved about to form a reconstruction. Darker yellow and darker green are medial views of premaxilla and maxilla. Note the long ascending process of the premaxilla and the palatal elements seen through the various openings all overlooked by those with firsthand access to the fossil. Epipterygoids are lepidosaur synapomorphies not present in protorosaurs.

Figure 2. Macrocnemus fuyuanensis (GMPKU-P-3001) in situ and as traced by the original authors, (middle) flipped with colors applied to bones, and (above) bone colors moved about to form a reconstruction. Darker yellow and darker green are medial views of premaxilla and maxilla. Note the long ascending process of the premaxilla and the palatal elements seen through the various openings all overlooked by those with firsthand access to the fossil. Epipterygoids are lepidosaur synapomorphies not present in protorosaurs.

Until now,
no one has ever positively identified lepidosaurian (slender strut-like) epipterygoids in a pterosaur. In the large reptile tree (LRT, 1737+ taxa) and the large pterosaur tree (LPT, 251 taxa) Bergamodactylus (MPUM 6009) nests as the basalmost pterosaur. Here is the skull in situ with DGS colors applied, as traced by Wild 1978 (above), and reconstructed in lateral and palatal views (below) based on the DGS tracings.

Figure 3. Bergamodactylus skull in situ and reconstructed. Wild 1978 tracing above.

Figure 3. Bergamodactylus skull in situ and reconstructed. Wild 1978 tracing above. Note the break-up of the jugal. Note the fusion of the ectopterygoids with the palatines producing ectopalaatines.

The lepidosaurian epipterygoids of Bergamodactylus
(slender bright green struts in the cheek/orbit area in figure 3), or any pterosaur over the last 200 years, are identified here for the first time, further confirming the lepidosaurian status of pterosaurs (Peters 2007, the LRT). Sorry I missed these little struts earlier. When you don’t think to look for them, you can overlook them.

Figure 5. Eudimorphodon epipterygoids (slender green struts).

Figure 4. Eudimorphodon epipterygoids (slender green struts).

Now you may wonder how many other pterosaurs
have overlooked epipterygoids? A quick look at Eudimorphodon reveals epipterygoids (Fig. 4, bright green struts). Other Triassic pterosaurs include:

  1. Austriadactylus SMNS 56342: slender strut present
  2. Austriadactuylus SC 332466: slender strut present
  3. Raeticodactylus : slender strut is present (identified on link as a stapes)
  4. Preondactylus: slender strut present
  5. Dimorphodon: amber strut over squamosal (Fig. 5 in situ image), 
  6. Seazzadactylus MFSN 21545: slender struts present, tentatively identified by Dalla Vecchia 2019, but as more than the slender struts they are) (Fig. 6).

The skull of Dimorphodon macronyx BMNH 41212.

Figure 5. The skull of Dimorphodon macronyx BMNH 41212. Above: in situ. Middle: Restored. Below: Palatal view. The slender yellow strut on top of the red squamosal in situ is a likely epipterygoid.

Figure 6. Seazzadactylus from Dalla Vecchia 2019. Here the epipterygoid struts are more correctly and less tentatively identified.

Figure 6. Seazzadactylus from Dalla Vecchia 2019. Here the epipterygoid struts are more correctly and less tentatively identified.

Hard to tell in anurognathids
where everything is crushed and strut-like. Hard to tell in other pterosaurs because the hyoids look just like epipterygoids. Given more time perhaps more examples will be documented that are obvious and irrefutable.

Added a few days later:

Added Figure. Here's the Triebold specimen of Pteranodon (NMC41-358) with epipterygoid splinters in bright green.

Added Figure. Here’s the Triebold specimen of Pteranodon (NMC41-358) with epipterygoid splinters in bright green.

Here’s the Triebold specimen of Pteranodon
(NMC41-358, added figure) with epipterygoid splinters in bright green. So start looking for the epipterygoid in every pterosaur. We’ll see if it is universal when more pterosaur specimens of all sorts are presented.


References
Dalla Vecchia FM 2019. Seazzadactylus venieri gen. et sp. nov., a new pterosaur (Diapsida: Pterosauria) from the Upper Triassic (Norian) of northeastern Italy. PeerJ 7:e7363 DOI 10.7717/peerj.7363
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.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Bergamodactylus
wiki/Huehuecuetzpalli
wiki/Homoeosaurus
wiki/Bavarisaurus

The Solomon Islands skink (genus Corucia) enters the LRT

Today the extant Solomon Islands skink
(Corucia zebrata, Gray 1855; Figs. 1, 2) enters the large reptile tree (LRT, 1714+ taxa). It nests basal to Gymnophthlamus + Vanzosaura and between Chalcides and Sirenoscincus.

Figure 1. The Solomon Islands skink (Corucia zebrata) is the largest skink on the planet, gives birth with a placenta and lives in communities.

Figure 1. The Solomon Islands skink (Corucia zebrata) is the largest skink on the planet, gives birth with a placenta and lives in communities.

This nesting comes as no surprise.
After all, skeletally Corucia is just another widely recognized skink, albeit with some unique reproductive and social qualities (see below).

Figure 2. The skink, Corucia zebrata with DGS colors added.

Figure 2. The skink, Corucia zebrata with DGS colors added.

Do not confuse Corucia with Carusia
(Fig. 3). The two are not the same, nor are they closely related.

Figure 1. Carusia intermedia, a basal lepidosaur close to Meyasaurus now, but looks a lot like Scandensia. Note the primitive choanae and broad palatal elements. None of the data I have shows the caudoventral process of the jugal, so I added it here from the description. Same with the epipterygoid.

Figure 3. Carusia intermedia, a basal lepidosaur close to Meyasaurus now, but looks a lot like Scandensia. Note the primitive choanae and broad palatal elements. None of the data I have shows the caudoventral process of the jugal, so I added it here from the description. Same with the epipterygoid.

Corucia zebrata
(Gray 1855, Figs. 1, 2) is the extant Soloman Islands skink, the largest known extant species of skink. Long chisel teeth distinguish this herbivorous genus. The tail is prehensile. This is one of the few species of reptile to live in communal groups. Rather than laying eggs, relatively large young are born after developing within a placenta. Single babies are typical. Twins are rare according to Wikipedia.

Removing all Carusia sister taxa in the LRT
fails to shift Carusia from its traditionally overlooked node basal to squamates.

The Wikipedia entry
on the ‘clade’ Carusioidea excludes great swathes of taxa relative to the LRT, so it mistakenly suggests that extinct Carusia is a member of the Squamata. Adding pertinent taxa solves that problem, as the LRT demonstrates.


References
Gray JE 1855. (1856). New Genus of Fish-scaled Lizards (Scissosaræ), from New Guinea. Annals and Magazine of Natural History, Second Series 18: 345–346.

wiki/Solomon_Islands_skink
wiki/Carusia
wiki/Carusioidea
http://www.markwitton.com
http://tetzoo.com

https://www.researchgate.net/publication/328388754_A_new_lepidosaur_clade_the_Tritosauria

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/

Another lepidosaur with a big antorbital fenestra

Quick backstory and summary:
Pterosaurs and their Middle Triassic precursors with a big antorbital fenestra are lepidosaurs (LRT 2020, Peters 2007). Macrocnemus is one of those Middle Triassic precursors, but this one is the only one has a large antorbital fenestra…by convergence.

Skull details on this specimen have been overlooked since 2007.
Macrocnemus fuyuanensis (Li, Zhao and Wang 2007; < 1 m in length; GMPKU P3001, Fig. 1), was the first and only member of this genus not considered conspecific by its authors (actually, no two are alike, see Fig. 3). Earlier we looked at the GMPKU specimen. Today the GMPKU specimen enters the large reptile tree (LRT, 1694+ taxa) today nesting with the T2472 specimen from Europe (Fig. 2).

Figure 1. Macrocnemus fuyuanensis (GMPKU-P-3001) in situ and as traced by the original authors, (middle) flipped with colors applied to bones, and (above) bone colors moved about to form a reconstruction. Darker yellow and darker green are medial views of premaxilla and maxilla. Note the long ascending process of the premaxilla and the palatal elements seen through the various openings all overlooked by those with firsthand access to the fossil. Epipterygoids are lepidosaur synapomorphies not present in protorosaurs.

Figure 1. Macrocnemus fuyuanensis (GMPKU-P-3001) in situ and as traced by the original authors, (middle) flipped with colors applied to bones, and (above) bone colors moved about to form a reconstruction. Darker yellow and darker green are medial views of premaxilla and maxilla. Note the long ascending process of the premaxilla and the palatal elements seen through the various openings all overlooked by those with firsthand access to the fossil. Epipterygoids are lepidosaur synapomorphies not present in protorosaurs.

This referred GMPKU specimen was brought to mind
when Scheyer et al. 2020 discussed in detail the larger holotype M. fuyuarnensis with the skull preserved in ventral view (IVPP V15001, Fig. 4). Scheyer et al. 2020 mistakenly considered it an archosauromorph due to taxon exclusion. Jiang et al. mistakenly considered it a protorosaurian due to taxon exclusion.

All prior workers also overlooked the twin epipterygoids
in the referred specimen (Fig. 1). This is a trait not found outside the Lepidosauria and is lost in several subclades of the Lepidosauria (e.g. Fenestrasauria).

All prior workers overlooked the tiny supratemporals,
which are easy to overlook unless you are looking for them based on phylogenetic bracketing. Taxon exclusion is, once again, the chief problem here. A poor tracing (e.g. Li et al. 2007; Jiang et al. 2011) is the secondary problem.

Figure 2. M. fuyuanensis GMPKU-P-3001 overall. This specimen nests with T2472 in figure 3.

Figure 2. M. fuyuanensis GMPKU-P-3001 overall. This specimen nests with T2472 in figure 3.

The antorbital fenestra
was previously (Li et al. 2007; Jiang et al. 2011) and recently (Scheyer et al. 2020) overlooked because earlier workers considered palatal bones to be rostral bones. That is repaired here (Fig. 1) using DGS methods.

Figure 1. Several Macrocnemus specimens to scale alongside the ancestral taxon in the LRT, Huehuecuetzpalli, and descendant taxa in the LRT, including Cosesaurus and the fenestrasaurs Sharovipteryx, Longisquama and Bergamodactylus. The similarities in transitional taxa should be obvious.

Figure 3. Several Macrocnemus specimens to scale alongside the ancestral taxon in the LRT, Huehuecuetzpalli, and descendant taxa in the LRT, including Cosesaurus and the fenestrasaurs Sharovipteryx, Longisquama and Bergamodactylus. The similarities in transitional taxa should be obvious.

The larger holotype IVPP V15001 specimen
(Fig. 4) preserves the skull upside down (mandible in ventral view). Other elements clearly show the pectoral girdle, pelvic girdle, manus and pes and other elements, more or less in articulation. These are typically scattered in European fossils of Macrocnemus.

Figure 7. The IVPP V15001 specimen of Macrocnemus fuyuanensis in situ. Colors and reconstructions added. Some disagreement here with the pectoral elements.

Figure 4. The IVPP V15001 specimen of Macrocnemus fuyuanensis in situ. Colors and reconstructions added. Some disagreement here with the pectoral elements. Note how the coracoids slide along the interclavicle bound by the sternum reidentified here from the original coracoid. The skull and mandibles are in the center in ventral view.

For those who forget how important the pectoral girdle is
in Macrocnemus and its descendants, others of you might remember the migration of the sternum to the interclavicle, the erosion if the anterior coracoid rim, the elongation of the scapula, the wrapping of the clavicles and the development of the anterior process of the interclavicle that gradually evolves to become the sternal complex in pterosaurs and their flapping precursors, the fenestrasaurs (Fig. 5). This is why it is vitally important to include more taxa in your analyses in order to keep the specimen you are describing in a proper phylogenetic context. All prior workers who studied Macrocnemus lack this context.

Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Figure  5. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

The Tritosauria (“third lizards”)
is a new squamate clade, now all extinct. The Tritosauria flourished in the Triassic, was reduced to only the Pterosauria during the Jurassic and Cretaceous, and became extinct thereafter. Several members have an antorbital fenestra, most in the lineage of pterosaurs. The GMPKU specimen has an antorbital fenestra convergent with those taxa.

In 2020 pterosaur experts
still have not presented a better hypothesis for the origin of pterosaurs, but prefer to follow their professors who taught them pterosaurs belong with dinosaurs (e.g. Avemetatarsalia, Ornithodira). When will the first one of them break away from promoting this myth?


References
Jiang D-Y, Rieppel O, Fraser NC, Motani R, Hao W-C, Tintori A, Sun Y-L and Sun Z-Y 2011. New information on the protorosaurian reptile Macrocnemus fuyuanensis Li et al., 2007, from the Middle/Upper Triassic of Yunnan, China. Journal of Vertebrate Paleontology 31: 2011-1237, DOI:10.1080/02724634.2011.610853
Li C, Zhao L and Wang L 2007.
A new species of Macrocnemus (Reptilia: Protorosauria) from the Middle Triassic of southwestern China and its palaeogeographical implication. Sci China Ser D: Earth Sci, 50(11): 1601–1605.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Scheyer TM, Wang W, Li C, Miedema F and Spiekman SNF 2020. Osteological re-description of Macrocnemus fuyuanensis (Archosauromorpha, Tanystropheidae) from the Middle Triassic of China. Vertebrata PalAsiatica. DOI: 10.19615/j.cnki.1000-3118.200525

wiki/Macrocnemus

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.