o Amniota |--Sauropsida `--o SYNAPSIDA `==Pelycosauria `==Therapsida `==Mammaliaformes `--Mammalia
The pelycosaurs (from Greek pelyx meaning 'bowl' and sauros meaning 'lizard') were smallish to large (up to 3 meters or more) primitive Late Paleozoic synapsid amniotes. They appeared during the Late Carboniferous and reached their acme in the early part of the Permian Period, remaining the dominant land animals for many millions of years. A few stragglers continued into the late Permian.
o Amniota `--o PELYCOSAURIA |--Caseasauria `--o--Varanopseidae `--o--Ophiacodontidae `--o--Edaphosauridae `--o--Haptodus `--o--Palaeohatteria `--o--Pantelosaurus `--o--Cutleria `--o--Sphenacodontidae `--+?-Tetraceratops `-- THERAPSIDA
- Phylum: Chordata
Environment: Semi-aquatic, terrestrial water margins, some forms may have lived in more upland environments
Ecology and Evolution
At least two pelycosaur clades independently evolved a tall sail, consisting of elongated vertebral spines: the edaphosaurids and the sphenacodontids. In life, this would have been covered by skin, and possibly functioned as a thermoregulatory device or for mating display. Pelycosaur fossils have been found mainly in Europe and North America, although some small, late-surviving forms are known from Russia and South Africa.