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.

 

 

 

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

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

Figure 1. Extant Draco flying with hands either grabbing the leading edge of the membrane or streamlining their hands on top of it. Images from Dehling 2016.

Gliding lizards
of the genus Draco (Figs. 1, 2) come in a wide variety of species. Similar but extinct gliding basal lepidosauriformes, like Icarosaurus (Fig. 2), form a clade that arose in the Late Permian and continued to the Early Cretaceous.

Figure 2. Two Draco species fully extending their rib membranes without the use of the hands.

Figure 2. Two Draco species fully extending their rib membranes without the use of the hands.

A recent paper
(Dehling 2016) reported, “the patagium is deliberately grasped and controlled by the forelimbs while airborne.” Evidently this ‘membrane-grab’ behavior has not been noted before. I wondered if the rib skin is indeed grasped, or does the forelimb merely fold back against the leading edge of the patagium in a streamlined fashion? Photographs of climbing Draco specimens (Fig. 2) show that the patagium  can fully extend without the aid of the forelimbs to stretch them further forward.

Figure 3. Icarosaurus. Note the tiny ribs near the shoulders. The bases for the strut-like dermal bones are the ribs themselves flattened and transformed by fusion to act like transverse processes, which sister taxa do not have. Note the length of the hands corresponds to the base of the anterior wing strut.

Figure 3. Icarosaurus. Note the tiny ribs near the shoulders. The bases for the strut-like dermal bones are the ribs themselves flattened and transformed by fusion to act like transverse processes, which sister taxa do not have. Note the length of the hands corresponds to the base of the anterior wing strut, a great place to rest the manus or grab the membrane.

A quick review of prehistoric gliding keuhneosaurs
(Fig. 3) show that the manus unguals are not quite as large and sharp as those of the pes and that the manus in gliding mode extends just beyond the shorter two anterior dermal struts so that the glider -may- have grasped the anterior struts in flight. Or may have rested the manus there. Remember, these are taxa unrelated to the extant Draco, which uses actual ribs to stretch its gliding membrane. The same holds true for the more primitive Coelurosauravus and Mecistotrachelos, which have not been traditionally recognized as basal kuehneosaurs.

* As everyone should know by now…
the so-called transverse processes in kuehneosaurs are the true ribs, only fused to the vertebrae. The ribs remain unfused to the vertebrae in the older and more primitive coelurosauravids. No sister taxa have transverse processes elongate or not.

References
Dehling M 2016. How lizards fly: A novel type of wing in animals.

Dr. David Unwin on pterosaur reproduction – YouTube

Dr. David Unwin’ talk on pterosaur reproduction 
was recorded at the XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, Teylers Museum, Haarlem, Netherlands and are online as a YouTube video.
Dr. Unwin is an excellent and engaging speaker.
However, some of the issues Dr. Unwin raises have been solved at www.ReptileEvolution.com
The virtual lack of calcite in pterosaur eggs were compared to lepidosaurs by Dr. Unwin, because pterosaurs ARE lepidosaurs.  See: www.ReptileEvolution.com/reptile-tree.htm
Lepidosaurs carry their eggs internally much longer than archosaurs, some to the point of live birth or hatching within hours of egg laying. Given this, pterosaurs did not have to bury their eggs where hatchlings would risk damaging their fragile membranes while digging out. Rather mothers carried them until hatching. The Mrs. T external egg was prematurely expelled at death, thus the embryo was poorly ossified and small.
Dr. Unwin ignores the fact that hatchlings and juveniles had adult proportions as demonstrated by growth series in Zhejiangopterus, Pterodaustro and all others, like the JZMP embryo (with adult ornithocheirid proportions) and the IVPP embryo (with adult anurognathid proportions).
Dr. Unwin also holds to the disproved assumption that all Solnhofen sparrow- to hummingbird-sized pterosaurs were juveniles or hatchlings distinct from any adult in the strata. So they can’t be juveniles (see above). Rather these have been demonstrated to be phylogenetically miniaturized adults and transitional taxa linking larger long-tailed dorygnathid and scaphognathid ancestors to larger short-tailed pterodactyloid-grade descendants, as shown at: www.ReptileEvolution.com/MPUM6009-3.htm
Thus the BMNH 42736 specimen and Ningchengopterus are adults, not hatchlings. And the small Rhamphorhynchus specimens are also small adults.

Earliest(?) stem squamate – SVP abstracts 2016

Klugman and Pritchard 2016
believe they have found the earliest lepidosaur stem squamate (see below). The large reptile tree finds earlier stem squamates (Fig. 1, click here to enlarge).
Earlier we looked at the wider and narrower definitions of the term ‘stem’.
Figure 1. CLICK TO ENLARGE. Stem taxa are closest ancestors to living taxa. Here basal diapsids and marine enaliosaurs are stem archosaurs. Triceratops is a stem bird. Captorhinids are stem turtles. Pterosaurs are stem squamates.

Figure 1. CLICK TO ENLARGE. Stem taxa are closest ancestors to living taxa. Here basal diapsids and marine enaliosaurs are stem archosaurs. Triceratops is a stem bird. Captorhinids are stem turtles. Pterosaurs are stem squamates. The colors here indicate the wider definition of ‘stem’.

From the Klugman and Pritchard abstract (abridged)
“Crown group lepidosaurs are highly diverse: they comprise more than 7,000 globally distributed extant species of lizards and snakes (Squamata), plus the single rhynchocephalian genus Sphenodon. The earliest known lepidosaurs are rhynchocephalians from the Late Triassic of Europe, (1) and this group quickly diversified and achieved a global distribution by the end of the Triassic. In contrast, early squamates have a sparse fossil record; their first representatives are found in the Early-Middle Jurassic of Laurasia (2). Although Rhynchocephalia and Squamata diverged in the Middle Triassic, a 40-50 million years ghost lineage exists for Squamata. Jurassic squamates are already considerably derived, and have already diversified into their extant groups, which testifies to a substantial gap in the known fossil record. Here we report on a new lepidosaur from a Norian microvertebrate site in Petrified Forest National Park, Arizona. This fossiliferous locality is from the Upper Blue Mesa Member of the Chinle Formation, and is dated to 221 mya. The depositional environment is a shallow anoxic lake, where skeletal elements preserved are disarticulated and often fragmentary. The site has yielded a diverse small vertebrate fauna, including the new lepidosaurs and several undescribed rhynchocephalians. Skeletal elements are represented by numerous small, delicate pleurodont maxilla and dentaries. We integrated the material of the new lepidosaurs into phylogenetic analyses of Permo-Triassic Diapsida and Mesozoic Lepidosauromorpha, using maximum parsimony, maximum likelihood, and Bayesian analysis. All analyses support the new taxon as the sister taxon to all other Squamata, (3) substantially reducing the ghost lineage of Squamata. This discovery indicates that the absence of squamate fossils in their early evolutionary history could be caused in part by collection bias towards larger, more robust specimens. This taxon provides a look into the early evolutionary history of squamates. It also adds direct evidence of yet another major lineage of extant terrestrial vertebrates to originate in the Triassic.”
Notes
  1. In the LRT Megachirella (Middle Triassic) is an earlier basal rhynchocephalian. Bavariasaurus (Late Jurassic) and
  2. Lacertulus (Late Permian; Fig. 2) are basal stem squamates. TA104 (Rößler et al. 2012), an unnamed Early Permian lepidosaur close to Saniwa in the varanid clade is the earliest lepidosaur I have encountered yet, although this is based on low-rez data. Based on these nestings, the original radiation of lepidosaurs must have occurred in the Permian and then enjoyed very long period of stasis.  Lacertulus is the oldest known lepidosaur and older than any Late Triassic Petrified Forest taxa. It does not have pleurodont (fused to the jaw) teeth.
  3. The LRT is an analysis that includes a long list of pro or proto-squamates and tritosaurs that are sisters to the Squamata. Palaegama (Late Permian), Tridentinosaurus (Early Permian) and Saurosternon (Latest Permian) are sisters to the Lepidosauria and they are basal to the highly derived Late Permian taxon, Coelurosauravus. So the original radiation of lepidosaurs and their lepidosauriform sisters must have been in the Early Permian. If one deletes Sphenodon, then another stem squamate would be Macroleter (Middle Permian). Earlier than this and you get into stem turtles.
Figure 1. Lacertulus, a basal squamate from the Late Permian

Figure 2. Lacertulus, a basal squamate from the Late Permian

References
Klugman B and Pritchard AC 2016. Earliest stem-squamate (Lepidosauria) from the Late Triassic of Arizona. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Rößler R, Zierold T, Feng Z, 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, 2012, v. 27, p. 814–834