Dalinghosaurus longidigitus (Ji 1998) Early Cretaceous was reported to be related to the modern-day lizards in the family Xenosauridae (Shinisaurus in China), Xenosaurus in Mexico and two extinct lizards, Exostinus and Carusia. One fossil skeleton of Dalinghosaurus includes ten juveniles (Evans and Wang 2005). Despite the disparity in limb length, Evans and Wang (2005) considered Dalinghosaurus a climber, not a biped. The elongated hind foot was equal in length to the rest of the hind limb.

In the large study Dalinghosaurus nested as more primitive, outside the Squamata (Iguania + Scleroglossa) + Tritosauria, as a sister to Homoeosaurus and derived from Gephyrosaurus. Thus a Late Permian sister to Dalinghosaurus and Homoeosaurus was the basal squamate from which all other squamates evolved.

Distinct from Homoeosaurus, the skull of Dalinghosaurus had a larger orbit and a deeper preorbital bone with a reduced lacrimal. The jugal and postorbital bones were relatively more gracile. The mandible was deeper with a longer, deeper retroarticular process.

The cervicals were longer. The dorsal ribs were much wider producing a flattened cross-section. The transverse processes of the anterior caudals were longer. The tail was longer and more robust.

The scapulocoracoid was fused and fenestrated anteriorly. The interclavicle is cruciform. The humerus, radius and ulna were more gracile. The metacarpals were longer.

The pubis was longer and the ischium was more robust. The feet were much longer and longer than the femur + tibia. The astragalus and calcaneum were co-ossified.

Here the two traditional squamate clades are joined by a third, now totally extinct. Lacertulus , Meyasaurus and Huehuecuetzpalli are at the base of the new clade, the Tritosauria or "third lizards". The Tritosauria is defined as Pteranodon, Lacertulus, their last common ancestor and all of its descendants.

At the base of all three clades is Dalinghosaurus. The Dalinghosauria includes Dalinghosaurus, Iguana, their last common ancestor and all of its descendants (in other words all lizards, snakes and pterosaurs).

The complete reptile family tree is here.

Evans SE and Wang Y 2005. The Early Cretaceous lizard Dalinghosaurus from China. Acta Palaeontologica Polonica 50 (4): 725–742. online pdf

Ji SA 1998. A new long−tailed lizard from the Upper Jurassic of Liaoning, China. In: Department of Geology, Peking University (ed.), Collected Works of International Symposium on Geological Science, Peking University, Beijing, China, pp 496–505. Seismological Press, Beijing.

wiki/Dalinghosaurus