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.
Li et al. have no idea what they’re dealing with phylogenetically. They relied on old invalidated hypotheses of relationships. They report the specimen:
- 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.
- 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.
- 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.
- 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.
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.
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.”
Distinct from Pectodens the new genus embryo has:
- 24 cervicals
- 29 dorsals
- 2 sacrals
- and about 64 caudals
Li et al overlooked:
- strap-like coracoids, strip-like clavicle and T-shaped interclavicle
- scattered manual elements
- pelvic girdle
- 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.
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.
Li C, Rieppel O, Fraser N C, in press. Viviparity in a Triassic marine archosauromorph reptile. Vertebrata PalAsiatica, online here.
Interesting that neck, tail, and limb elongation suddenly became so common in the Mid-Late Triassic across multiple taxa, doncha think? The fact that many of these taxa were only distantly related would seem to rule out genetics as the driver.
This time, seems like niche was the driver.