SVP abstracts 2017: The earliest lepidosaurs

Simöes 2017 brings us
new insights into the origin and early radiation of lepidosaurs, but seems to focus on the squamate side of that equation. Earlier Simöes brought us new data on Ardeosaurus (late Jurassic proto-snake) and Calanguban (Early Cretaceous, late-surviving basal squamate).

From the abstract:
“The origins and early radiation of lepidosaurs remain largely enigmatic by several factors, including:

  1. the oldest unequivocal fossils currently attributed to the Squamata are from the Middle Jurassic;
  2. available studies of broad level/deep-time diapsid reptile relationships provide very limited sampling of either fossil or living lepidosaurs (often, Squamata being represented as a single terminal unit);
  3. morphological and molecular evidence of squamate relationships disagree on what is the earliest squamate clade (iguanians vs dibamids and geckoes);
  4. among others.”

“Here, I provide a new phylogenetic dataset with a deep sampling of the major diapsid and
lepidosaurian lineages (living and fossil) at the species level in order to identify the
composition and early evolution of lepidosaurs. All taxon scorings were based on
personal observation of specimens and/or 3D CT scans from 51 collections from around
the world, making it the largest species sample ever collected for investigating the origin
of lepidosaurs—over 150 species.”

“The results indicate novel relationships among diapsids and re-shape the lepidosaurian
tree of life. Previously proposed early lepidosaurs are found to belong to other lineages of
reptiles. Importantly, heretofore unrecognized squamate fossils are found as the earliest
squamates, dating back to the Early Triassic, thus filling what was thought to be a fossil
gap of at least 50 million years. In most results (morphology only and combined data)
geckoes are the earliest squamate crown clade, iguanians are always found as later
evolving squamates, and scincomorphs are polyphyletic, thus dramatically differing from
previous morphology based studies, but agreeing with the molecular data.”

Figure 1. Lacertulus, a basal squamate from the Late Permian

Figure 1. Lacertulus, a basal protosquamate from the Late Permian

How does this data compare
to the large reptile tree? The LRT has 140 lepidosaur taxa, but I don’t get the feeling that Simöes included tritosaurs and protosquamates, some of which extend back to the Late Permian (Lacertulus, Fig. 1). If Simöes does not include those clades, the hypothesis needs more taxa. The abstract is enigmatic with regard to which early lepidosaurs now belong to other lineages and which unrecognized squamates are now earliest squamates.

But I like that Simöes is looking at more taxa!!

Unfortunately,
Simöes does not provide outgroup taxa in the abstract. I’m guessing he did not test a wide gamut of taxa, like the LRT, to see if they were lepidosaurs or not. That’s how you recover protosquamates and tritosaurs. In the LRT geckoes are not the basalmost squamates and scincomorphs are not polyphyletic.

I look forward to this paper!!

References
Simöes TR 2017. The origin and early evolution of lepidosaurian reptiles. Abstracts from the Society of Vertebrate Paleontology 2017.

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Shringasaurus: new rhynchocephalian lepidosaur with horns

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

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

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

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

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

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

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

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

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

No Wiki page yet.

What is the enigmatic Otter Sandstone (Middle Triassic) diapsid?

Coram, Radley and Benton 2017
presented a “small diapsid reptile [BRSUG 29950-12], possibly, pending systematic study, a basal lepidosaur or a protorosaurian.” According to Coram et al. “The Middle Triassic (Anisian) Otter Sandstone was laid down mostly by braided rivers in a desert environment.”

Figure 1. The Middle Triassic Otter Sandstone diapsid BRSUG 29950-12 under DGS nested with basalmost lepidosaurs like Megachirella.

Figure 1. The Middle Triassic Otter Sandstone diapsid BRSUG 29950-12 under DGS nested with basalmost lepidosaurs like Megachirella. Skeleton is exposed in ventral (palatal) view.

The LRT is here to nest and identify published enigmas
The large reptile tree (LRT 1041 taxa) nests BRSUG 29950-12 with the basalmost lepidosaur Megachirella. They are a close match and preserve nearly identical portions of their skeletons (Fig. 2). Megachirella was originally considered a sister to Marmoretta, another basal sphenodontian from the much later Middle/Late Jurassic.

FIgure 2. Megachirella (Renesto and Posenato 2003) is a sister to the BSRUG diapsid.

FIgure 2. Megachirella (Renesto and Posenato 2003), also from Middle Triassic desposits, is a sister to the BSRUG diapsid and provides a good guide for its eventual reconstruction.

At the base of the Lepidosauria
in the LRT nests Megachirella, derived from a sister to Sophineta (Early Triassic) and Saurosternon + Palaegama (Latest Permian) and kin. Sisters to Megachirella within the Lepidosauria include the tritosaurs Tijubina + Huehuecuetzpalli (Early Cretaceous), Macrocnemus (Middle Triassic) and the prosquamate Lacertulus (Late Permian). Also similar and related to Palaegama is Jesairosaurus (Middle Triassic). So the genesis of the Lepidosauria is Late Permian. The initial radiation produced taxa that continued into the Early Cretaceous. The radiation of derived taxa continued with three major clades, only one of which, the Tritosauria, is now completely extinct.

Note
It is important to remember that lepdiosaurs and protorosaurs are not closely related, but arrived at similar bauplans by convergence, according to the LRT. The former is a member of the new Lepidosauromorpha. The latter is a member of the new Archosauromorpha. Last common ancestor: Gephyrostegus and kin.

Nesting at the base of the Lepidosauria
in the Sphenodontia clade makes the BSRUG specimen an important taxon. Let’s see if and when this taxon is nested by academic workers that they include all of the pertinent taxa and confirm or re-discover the Tritosauria. The LRT provides a good list of nearly all of the pertinent taxa that should be included in that future study, many of which are listed above. Based on that list, the BSRUG specimen is a late-survivor of a perhaps Middle Permian radiation of basal lepidosaurs.

References
Coram RA, Radley JD and Benton MJ 2017. The Middle Triassic (Anisian) Otter Sandstone biota (Devon, UK): review, recent discoveries and ways ahead. Proceedings of the Geologists’ Association in press. http://dx.doi.org/10.1016/j.pgeola.2017.06.007

Another long-necked embryo tritosaur: Li et al. in press

This appears to be
yet another Tanystropheus-like and Dinocephalosaurus-like taxon, yet not closely related to either. Earlier we looked at another similar embryo, still within its mother.

Li, Rieppel and Fraser in press (2017)
bring us a new curled up (as if in an egg, but without a shell) embryo from the Guanling Formation (Anisian), Yunnan province, China (Figs. 1, 2). The specimen is unnamed and not numbered. It appears to combine the large head and eyes of langobardisaurs with the short limbs and many cervical vertebrae of Dinocephalosaurus. Please remember, in this clade, juveniles do not have a short rostrum and large eyes unless their parents also had these traits.

Figure 1. The unnamed and not numbered Triassic embryo Li et al. assign to a new species close to Dinocephalosaurus.

Figure 1. The unnamed and not numbered Triassic embryo Li et al. assign to a new species close to Dinocephalosaurus. At 72 dpi monitor resolution, this image is 2.5x life size. Here bones are colorized, something Li et al. could have done, but avoided. I’m happy to report that the line drawing was traced by Li et al. on their own photo. The two are a perfect match.

Unfortunately
Li et al. have no idea what they’re dealing with phylogenetically. They relied on old invalidated hypotheses of relationships. They report the specimen:

  1.  is a marine protorosaur and an archosauromorph – actually it is a marine tritosaur lepidosaur. Taxon exclusion and traditional bias hampered the opinion of Li et al. They did not perform a phylogenetic analysis.
  2. is closely related to Dinocephalosaurus – actually it is more closely related to the much smaller, but longer-legged Pectodens (Figs. 4, 5). In the large reptile tree (LRT, 1036 taxa) 8 steps are added when the embryo is force-nested with Dinocephalosaurus. The embryo is distinct enough that the new specimen deserves a new genus.
  3. confirms viviparity – probably not (but see below). The specimen is confined within an elliptical shape (Fig. 1), as if bound by an eggshell or membrane, which was not preserved. Perhaps, as in pterosaurs and many other lepidosaurs, the embryo was held within the mother’s body until just before hatching, within the thinnest of egg shells and/or membranes.
  4. is too immature to describe it as a new taxon – not so. Tritosaur lepidosaurs (from Huehuecuetzpalli to Pterodaustro) develop isometrically. Thus, full-term embryos and hatchlings have adult proportions.
Figure 2. The specimen from figure 1 unrolled for clarity. This specimen most closely resembles the basal langobardisaur, Pectodens, not Dinocephalosaurus. Remember, tritosaurs develop isometrically. Embryos closely resemble adults. That's why three scale bars are included.

Figure 2. The specimen from figure 1 unrolled for clarity. This specimen most closely resembles the basal langobardisaur, Pectodens, not Dinocephalosaurus. Remember, tritosaurs develop isometrically. Embryos closely resemble adults. That’s why three scale bars are included. This specimen has feeble limbs but a strong swimming tail, distinct from that of Dinocephalosaurus.

Li et al. report
“In the fossil record only oviparity and viviparity can be distinguished, Ovoviviparity of different intermediate stages, which is often observed in modern squamates would then be referred to the category of viviparity, whatever the stages of maturity and nutritional patterns are.” Yes, they correctly report ovoviviparity in squamates, which are the closet living relatives of tritosaur lepidosaurs. That’s exactly what we have here.

Figure 1. The new Dinocephalosaurus has traits the holotype does not, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with an elongate pedal digit 4.

Figure 3. The new Dinocephalosaurus has traits the holotype does not, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with an elongate pedal digit 4.

Li et al. report,
“[The] skeleton is preserved tightly curled so as to produce an almost perfect circular outline, which is strongly indicative of an embryonic position constrained by an uncalcified egg membrane.”

Figure 2. Pectodens skull traced using DGS techniques and reassembled below.

Figure 4. Pectodens skull traced using DGS techniques and reassembled below. No sclerotic ring here. 

Distinct from Pectodens the new genus embryo has:

  1. 24 cervicals
  2. 29 dorsals
  3. 2 sacrals
  4. and about 64 caudals
Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Figure 5. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017. The skull shown here is the original reconstruction. Compare it to figure 4.

Li et al overlooked:

  1. strap-like coracoids, strip-like clavicle and T-shaped interclavicle
  2. scattered manual elements
  3. pelvic girdle
  4. ectopterygoid, jugal, articular, angular, surangular

Li et al. report:
“The fewer cervical vertebrae (24 as opposed to 33 (based on an undescribed specimen kept in the IVPP)), and the presence of sclerotic plates are features inconsistent with Dinocephalosaurus.This embryo therefore documents the presence of at least one additional dinocephalosaur-like species swimming in the Middle Triassic of the Eastern Tethys Sea.

“Scleral ossicles have previously not been described in any protorosaur.”
– but they are common in tritosaur lepidosaurs, like pterosaurs.

Figure 6. Pectodens adult compared to today's embryo and its 8x larger adult counterpart after isometric scaling.

Figure 6. Pectodens adult compared to today’s embryo and its 8x larger adult counterpart after isometric scaling. Looks more like Pectodens than Dinocephalosaurus, doesn’t it? See taxon inclusion WORKS! Sclerotic rings were omitted here to show skull bones. The ring would have had a smaller diameter if if were surrounding a sphere, rather than crushed flat. 

A word to traditional paleontologists:
Don’t keep digging yourself deeper into invalidated hypotheses and paradigms. Use the LRT, at least for options.

Don’t give up on naming embryos
and adding them to phylogenetic analysis, especially if they are tritosaur lepidosaurs. Hatchlings nest with adults so you can used hatchlings in analysis.

Don’t avoid creating reconstructions.
That’s a great way to discover little splinters of bone, like clavicles and coracoids, that would have been otherwise overlooked.

The LRT is here for you.
BETTER to check this catalog prior to submission rather than have your work criticized for being unaware of the latest discoveries or overlooking pertinent taxa AFTER publication.

References
Li C, Rieppel O, Fraser N C, in press. Viviparity in a Triassic marine archosauromorph reptile. Vertebrata PalAsiatica, online here.

Magnuviator, another basal scleroglossan.

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

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

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

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

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

Lacerta: where is the upper temporal fenestra?

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

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

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

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

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

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

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

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

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

Lacerta viridis images online
wiki/Lacerta

Scale models from the vault

You can also title this post: Toys for Christmas.

Yesterday I presented
several full scale models of prehistoric reptiles. Today, some scale models are presented.

Figure 1. Camarasaurus adult scale model.

Figure 1. Camarasaurus adult scale model.

Camarasaurus (Fig. 1) is a Late Jurassic sauropod.

Figure 2. Mosasaurus scale model.

Figure 2. Mosasaurus? scale model.

Mosasaurus, or is this Tylosaurus (Fig. 2)? I can’t remember. The belly is sitting on a ‘rock’.

Figure 3. Kronosaurus scale model.

Figure 3. Kronosaurus scale model.

Kronosaurus (Fig. 3) is here based on the Yale skeleton, which was revised here with a bigger belly among other traits.

Figure 4. Styracosaurus and Albertasaurus to scale.

Figure 4. Styracosaurus and Albertasaurus to scale.

Styracosaurus (Fig. 4) is a ceratopsian, derived from Yinlong. Albertasaurus is a theropod, close to Tyrannosaurus.

Figure 5. Tapinocephalus scale model.

Figure 5. Tapinocephalus scale model.

Tapinocephalus (Fig. 5) is an herbivorous tapinocephalid, close to Moschops.

Figure 6. Anteosaurus scale model.

Figure 6. Anteosaurus scale model.

Anteosaurus (Fig. 6) is an anteosaur known from the skull only, close to Titanophoneus, which here provides the body proportions.

These were produced 
back in my heyday, as models for paintings in books, and just to see how they would turn out. Most are made of Sculpey over a wire frame. After baking the soft clay turns into a hard plastic. So far these all remain on my shelves.