What is Yabeinosaurus?


Yabeinosaurus reconstructed.

Figure 1. Yabeinosaurus reconstructed. Formerly a gekkotan. Now a basal member of the Anguimorpha. Judging by size and the new Evans and Wang (2011) report, this specimen must be a juvenile.

From a recent SVPCA abstract
Yabeinosaurus (Endo and Shakima 1942) was an Early Cretaceous lizard from China. Evans and Wang (2011)  reported, “Yabeinosaurus was one of the first tetrapods to be described from the now famous Early Cretaceous Jehol Biota of north-eastern China. However, although it was correctly identified as a lizard its phylogenetic position was misunderstood for decades due to poor preservation, limited access to the material, and the subsequent loss of the holotype during WW2. As the original specimens (and a recently erected neotype) appeared to be weakly ossified, many authors attributed Yabeinosaurus to the Gekkota, but the recovery of new specimens from the Yixian and overlying Jiufotang formations (125-120 mya) has changed our perceptions. The type specimens are small with thin bones because they are immature. Yabeinosaurus adults were robust and relatively large (~300 mm SVL), probably reaching adult size over several seasons. New phylogenetic analyses place Yabeinosaurus and its sister taxon, the near contemporary Japanese Sakurasaurus, on the scleroglossan stem. Importantly, some of the new specimens also provide an insight into the biology of Yabeinosaurus. Three preserve vertebrate remains, predominantly fish bones, in the gut. Fish eating is reportedly rare in living lizards, being restricted to the small clade comprising Shinisaurus, Lanthanotus and Varanus, all of which forage in and around freshwater.”

Lizard family tree including Yabeinosaurus.

Figure 2. Lizard family tree including Yabeinosaurus (Evans and Wang 2012).

A paper by Evans and Wang (2012) is just out with much the same information in its abstract. The Evans and Wang (2012) tree is shown in figure 2. (Note their basal nesting of Ardeosaurus and Eichstattisaurus, which the larger study nested with Adriosaurus and snakes, a subject we looked at earlier.)

Based on data provided by Evans, Wang and Li (2005), and a much larger taxon list, Yabeinosaurus was nested here at the base of the Anguimorpha, surrounded by many of the same taxa used by Evans and Wang (2012) and more. Carusia was a sister at the base of the scincomorpha. Cryptolacerta and Bahndwivici were sisters at the base of the Platynota (Varanoidea).

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
Endo R and Shikama T 1942. Mesozoic reptilian fauna in the Jehol mountainland, Manchoukuo. Bulletin of the Central National Museum of Manchoukuo 3: 1–19.
Evans SE, Wang Y and Li C 2005. The early Cretaceous lizards genus Yabeinosaurus from China: resolving an enigma. Journal of Systematic Palaeontology 3(4): 319-335.
Evans SE and Wang Y 2011. The Early Cretaceous Chinese lizard Yabeinosaurus: insights from new specimens – SVPCA 2011 online
Evans SE, Wang Y and Li C 2012. New material of the Early Cretaceous lizard Yabeinosaurus from China. Cretaceous Research 34: 48-60.

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