Pelycosaur
Pelycosaur (/ˈpɛlɪkəˌsɔːr/ PEL-ih-kə-sor) is an older term for basal or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term mammal-like reptile had been used, and pelycosaur was considered an order, but this is now thought to be incorrect, and seen as outdated.
| Pelycosaurs Temporal range: Pennsylvanian - Capitanian, | |
|---|---|
| Mounted skeleton of Dimetrodon mileri, Harvard Museum of Natural History | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Superclass: | Tetrapoda |
| Clade: | Reptiliomorpha |
| Clade: | Amniota |
| Clade: | Synapsida |
| Informal group: | †Pelycosauria Cope, 1878 |
| Groups included | |
| Cladistically included but traditionally excluded taxa | |
Because it excludes the advanced synapsid group Therapsida, the term is paraphyletic and contrary to modern formal naming practice. Thus the name pelycosaurs, similar to the term mammal-like reptiles, had fallen out of favor among scientists by the 21st century, and is only used informally, if at all, in the modern scientific literature. The terms stem mammals, protomammals, and basal or primitive synapsids are used where needed, instead.