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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mammal-like reptile was used, and Pelycosauria was considered an order, but this is now thought to be incorrect and outdated. The terms stem mammals, protomammals, and basal or primitive synapsids are instead used where needed.
Because Pelycosaur excludes its own descendants, 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, fell out of favor among scientists by the 21st century, and is only used informally, if at all, in the modern scientific literature.
The modern word was created from Greek pélyx meaning 'basin' and saûros meaning 'lizard'. The term pelycosaur has been fairly well abandoned by paleontologists because it no longer matches the features that distinguish a clade.
In phylogenetic nomenclature, "Pelycosauria" is not used formally, since it does not constitute a group of all organisms descended from some common ancestor (a clade), specifically excluding therapsids, which are descended from pelycosaurs. Instead, it represents a paraphyletic "grade" of basal synapsids leading up to the clade Therapsida.
Eupelycosauria is used as a proper monophyletic group to designate the clade that includes most pelycosaurs, along with the Therapsida and Mammalia. Caseasauria a pelycosaur side-branch, or clade, that did not leave any descendants.[citation needed]
The pelycosaurs appear to have been a group of synapsids that have direct ancestral links with the mammals, having differentiated teeth and a developing hard palate. The pelycosaurs appeared during the Late Carboniferous and reached their apex in the early part of the Permian, remaining the dominant land animals for some 40 million years. A few continued into the Capitanian, but they experienced a sharp decline in diversity in the late Kungurian. They were succeeded by the therapsids.
Some species were quite large, growing to a length of 3 metres (10 ft) or more, although most species were much smaller. Well-known pelycosaurs include the genera Dimetrodon, Sphenacodon, Edaphosaurus, and Ophiacodon.
Pelycosaur fossils have been found mainly in Europe and North America, although some small, late-surviving forms are known from Russia and South Africa.
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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 was used, and Pelycosauria was considered an order, but this is now thought to be incorrect and outdated. The terms stem mammals, protomammals, and basal or primitive synapsids are instead used where needed.
Because Pelycosaur excludes its own descendants, 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, fell out of favor among scientists by the 21st century, and is only used informally, if at all, in the modern scientific literature.
The modern word was created from Greek pélyx meaning 'basin' and saûros meaning 'lizard'. The term pelycosaur has been fairly well abandoned by paleontologists because it no longer matches the features that distinguish a clade.
In phylogenetic nomenclature, "Pelycosauria" is not used formally, since it does not constitute a group of all organisms descended from some common ancestor (a clade), specifically excluding therapsids, which are descended from pelycosaurs. Instead, it represents a paraphyletic "grade" of basal synapsids leading up to the clade Therapsida.
Eupelycosauria is used as a proper monophyletic group to designate the clade that includes most pelycosaurs, along with the Therapsida and Mammalia. Caseasauria a pelycosaur side-branch, or clade, that did not leave any descendants.[citation needed]
The pelycosaurs appear to have been a group of synapsids that have direct ancestral links with the mammals, having differentiated teeth and a developing hard palate. The pelycosaurs appeared during the Late Carboniferous and reached their apex in the early part of the Permian, remaining the dominant land animals for some 40 million years. A few continued into the Capitanian, but they experienced a sharp decline in diversity in the late Kungurian. They were succeeded by the therapsids.
Some species were quite large, growing to a length of 3 metres (10 ft) or more, although most species were much smaller. Well-known pelycosaurs include the genera Dimetrodon, Sphenacodon, Edaphosaurus, and Ophiacodon.
Pelycosaur fossils have been found mainly in Europe and North America, although some small, late-surviving forms are known from Russia and South Africa.