The Lanthanosuchidae are an extinct group of anapsid procolophonomorphs parareptiles. The fossils of several species have been found in about 268-255 million years. The Soviet paleontologist Ivan Antonovich Efremov introduced the taxon to 1946.
The distinguishing feature of Lanthanosuchids is its broad, extremely flat skull. This was considered as an adaptation to an aquatic lifestyle, future studies are questioned this interpretation. Perhaps the animals fed on insects and larvae, and pushed their head flattened to forage in the litter of the forest soil under leaves and other material. The skull inside it offered no room for jaw muscles, so the muscles were outside and had a skull opening behind the eye socket to the jaw bone connected.
The systematic position of Lanthanosuchidae in the phylogenetic tree of terrestrial vertebrates has long been under discussion. In the past they were regarded as members of the Seymouriamorpha, probably because of the skull was sculpted out by distinct ridges and pits. This probably served to reinforce the cranium. Also, one belonging to the Diadectomorpha was proposed. Today they are considered as belonging to the extinct amniotes Group Parareptilia that you drew earlier as a core group of turtles into consideration. According to recent studies, the Lanthanosuchids closely related to the early parareptile Acleistorhinus. The strong Skuplturierung the skull was not a specific feature (Autapomorphie) of lanthanosuchids, she was in the early anapsid seymouriamorphs and widespread. A lateral temporal window was also at least in some taxa of early Anapsiden before.