Sakurasaurus – a basal varanid not far from other major clades

Sakurasaurus sp. (SBEI 199, Evans and Manabe 2008, Early Cretaceous, Japan) is represented by a single completely disarticulated specimen considered a sister to its contemporary, Yabeinosaurus. The holotype (Evans and Manabe 1999) was considered a possible scincomorph (family of skinks) based on jaw material.

Evans and Manabe 2008 nested SBEI 199 with Yabeinosaurus, Ardeosaurus, Scandensia and all other squamates in order of increasing distance. The large reptile tree changes that slightly, nesting Sakurasaurus with Yabeinosaurus at the base of the varanids and the varanids are sister to Tchingisaurus and the geckos + Ardeosaurus at the base of the clade of snakes and their kin. Scandensia nests as the most basal squamate. The differences in the two tree topologies can be largely ascribed largely to taxon exclusion in the Evans and Manabe 2008 tree.

The reconstruction by Evans and Manabe (2008) was done freehand (Fig. 1). The reconstruction offered here was done by copying and pasting disarticulated skull elements from Evans and Manabe into their in vivo positions (Fig. 1) using the second half of the DGS method. It might be better if more paleontologists tried this method, but freehand yielded similar results.

Figure 1. Sakurasaurus as originally reconstructed freehand (on the left) and as reconstructed using DGS methods of copying and pasting disarticulated elements into their in vivo positions. Click to enlarge.

Figure 1. Sakurasaurus as originally reconstructed freehand (on the left) and as reconstructed using DGS methods of copying and pasting disarticulated elements into their in vivo positions. Click to enlarge. Here the former coronoid is reidentified as a pterygoid. The postfrontal/postorbital is only a postfrontal. The teeth are not so sharp.The quadrate has a different shape.  Note the maxillary palatal process, which becomes expanded in varanids.

 

References
Evans SE and Manabe M 1999. Early Cretaceous lizards from the Okurodani Formation of Japan. Geobios, 32, 889–899.
Evans SE and Manabe M 2008. The Early Cretaceous lizards of eastern Asia: New material of Sakurasaurusa from Japan. Special Papers in Palaeontology 81:43-59.

 

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