ID-ing the Enigmatic Daohugou Lizard IVPP V1347

This entry was updated September 13, 2013.
Evans and Wang (2009) introduced us to a complete and largely articulated tiny lizard from the Daohugou horizon (Late Jurassic/Early Cretaceous). They considered it a scansorial juvenile with a slender body and relatively long limbs and extremities. They found the phylogenetic placement “problematic,” but considered it a possible scleroglossan due to the high presacral count of 27.

Figure 2. The enigmatic Daohugou lizard reconstucted. It was a late-surviving sister to  the basal tritosaur lepidosaur, Lacertulus.

The Evans and Wang (2009) Assessment
The Daohugou lizard was considered a juvenile due to the lack of fusion of the skull elements. The bones are extremely thin and prone to breakage. The in situ bones are mineral-tinted dark, medium and very light rust/brown, so that can be confusing. My tracing (Fig. 2) found a fused parietal. I used the DGS (digital graphic segregation) method to find more bones.  Evans and Wang (2009) considered the skeleton preserved in ventral view, but the mandible (light blue in figure 2) is beneath the skull and no palatal parts were identified by Evans and Wang (2009). A pterygoid (in deep purple) is preserved beneath the scleral ring and postorbital elements.

Figure 2. Click to enlarge. The skull of the Daohugou lizard IVPP V1347. At left, in situ. Middle as traced using DGS methods. At right, as figured by Evans and Wang 2005.

Analysis
Added to the large study, the Daohugou enigma nests with Lacertulus, a basal tritosaur, outside of the Squamata (Iguania + Scleroglossa). Sister taxa display similar fusion traits, so the ontogenetic age cannot be ascertained and no allometric guesswork should be attempted. Juveniles were similar to adults in this clade. The torso was not as short, nor the femur quite as long as in Lacertulus. The tail was attenuated and the digits indicate a scansorial (climbing) niche.

The Tritosauria keeps filling up with these enigmas!

References
Evans SE and Wang Y 2009. A long-limbed lizard from the Upper Jurassic/Lower Cretaceous of Daohugou, Ningcheng, Nei Mongol, China. Vertebrata PalAsiatica 47: 21–34.