Colobomycter pholeter (Vaughn 1958, Modesto and Reisz 2008, UWBM 95405), Lower Permian ~278 mya, was originally considered a caseid pelycosaur, like Eothyris. Later, Modesto and Reisz (2008) and MacDougall et al. (2016) considered it a "parareptile" close to Acleistorhinus. Actually Vaughn was partly right. It is derived from Eothyris, but neither are pelycosaurs.
Until June 2016, only the rostrum was known. A reconstruction traced from the Modesto and Reisz (2008) paper (above) differs from their published reconstruction, which adds postorbital bones and tooth tips among other detail differences. Vaughn (1958) reported impressions of the posterior maxilla and additional skull roof bones.
Compared to Eothyris, the naris and teeth of Colobomycter were larger. The maxilla was taller, reducing the external appearance of the lacrimal. The tip of the mandible was deeper. Although unknown at present, it appears likely that a lateral temporal fenestra was present.
The complete reptile family tree is here.