Protorosaurus speneri (Seeley 1888) Late Permian ~260 mya, 2 m in length, was originally considered ancestral to lizards, but it is not related according to the present tree. Protorosaurus was derived from a sister to Prolacerta and was a sister to Boreopricea and Pamelaria.
Distinct from Prolacerta, the skull of Protorosaurus had larger nares and a shallower premaxilla. The jugal was more gracile. The nasals were longer and the frontals were shorter giving Protorosaurus a longer rostrum.
The cervicals were massive and slightly longer overall. The dorsal neural spines were taller. That tail had taller neural spines and shorter chevrons.
The scapula was concave anteriorly, losing the plate-like anterior rim found in Prolacerta. The forelimb was more robust with larger unguals.
The pelvis was shorter. The hind limbs was more robust and digit V was not so hook-like.