Milleropsis pricei (Gow 1972) Early Permian ~290 mya, ~20 cm in length, was originally considered a milleretid close to Milleretta and a captorhinid (close to Captorhinus). Here Milleropsis was derived from a sister taxon to Heleosaurus and it phylogenetically preceded Eudibamus and Petrolacosaurus at the base of the Diapsida. The fossil is poorly known, but the skull, manus and pes provide many of the diagnostic characters.
Distinct from Heleosaurus, the skull of Milleropsis had a wider set of parietals and a smaller parietal opening. The lower temporal arch was missing by reduction of the quadratojugal. The maxilla does not appear to disconnect the lacrimal and naris, but that part of the fossil is damaged or the interpretation of Heleosaurus may be mistaken. The naris was probably closer to the jaw tips. The mandible had a slightly higher coronoid process. The transverse process of the pterygoid leaned anteriorly. The anterior pterygoids were separated along with the posterior vomers.
The vertebral column is not well known, but the caudal series is very long attenuated with little to no trace of any chevrons.
The scapula was distinct from the coracoid and dorsally was reduced to a thin strap. Metacarpal 3 was longer than mc4. The manus was larger with digits 3 and 4 subequal.
The ilium has a small anterior process and a reduced posterior process. The pubis and ischium were not separated. The pubis had a dorsal process.
The calcaneum was elongated, producing a pseudo tuber. Metatarsals 3 and 4 were subequal. The penultimate phalanges were short. Metatarsal V was elongated.
Millerosaurus ornatus (Broom 1948, Watson 1957) Late Permian (Changhsingian, 30 cm est length) is based on a chimaera of over a dozen skeletons with many common elements distinct from one another. Millerosaurus has been removed from future revisions of the large reptile tree.