colleagues also dispute the supposed semiaquatic lifestyle of the caseids on the fact that the latter possess no morphological adaptations to an aquatic lifestyle and, in the case of the species Cotylorhynchus romeri, on the interpretation that this animal lived in a dry environment for part of the year as indicated by the presence of numerous skeletons of the amphibian Brachydectes preserved in aestivation and of the lungfish Gnathorhiza, another well-known aestivator. In 2022, Werneburg and colleagues proposed a somewhat different semiaquatic lifestyle, in which large caseids like Lalieudorhynchus (whose bone texture is even more osteoporotic than in Cotylorhynchus) would be ecological equivalents of modern hippos, passing part of their time in the water (being underwater walkers rather than swimming animals) but coming on dry land for food. Evolution Caseids first appear in the fossil record at the end of the Carboniferous and are already present in both North America and Europe with small predatory forms like Eocasea and Datheosaurus. These faunivorous caseids also exist at the beginning of the lower Permian, such as Callibrachion, and may have existed until the base of the middle Permian with Phreatophasma. During the Permian, the representatives of the clade mainly evolved towards herbivory. These herbivorous caseids experienced an important evolutionary radiation during the second half of the lower Permian by becoming, with the moradisaurine captorhinid eureptiles, the main herbivores of terrestrial ecosystems instead of edaphosaurids and diadectids. The decline of edaphosaurids and the propagation of caseids coincides with an aridification of the environment that occurred from the Artinskian and which would have favored the caseid expansion. Sedimentological and taphonomic data indicate that the majority of edaphosaurids favored humid habitats (their remains are found mainly in lacustrine and marshy deposits) while herbivorous caseids generally lived in drier biotopes where ponds and streams water were ephemeral. The last caseids date from the Middle Permian and are mainly known in Europe with Phreatophasma and Ennatosaurus from the Roadian-Wordian of Russia, Alierasaurus from the Roadian-(Wordian?) of Sardinia, and Lalieudorhynchus from the late Wordian-early Capitanian of southern France. In North America, Angelosaurus romeri and Cotylorhynchus bransoni from the Chickasha Formation in Oklahoma probably date to the early Roadian, while the caseids from the San Angelo Formation in Texas are slightly older and may straddle the Kungurian-Roadian boundary but it is not yet clear whether they date from the latest Kungurian or from the earliest Roadian. Paleobiogeography Caseid fossils