Pelycosaur

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Pelycosaurs

Conservation status: Fossil

Dimetrodon.jpg
Dimetrodon grandis skeleton at the
National Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Superclass: Tetrapoda
Class: Synapsida
Order: Pelycosauria

Cope, 1878

Suborders and families

Caseasauria

Eothyrididae
Caseidae

Eupelycosauria

Varanopseidae
Ophiacodontidae
Edaphosauridae
Sphenacodontidae


The pelycosaurs (from Greek pelyx meaning 'bowl' and sauros meaning 'lizard') were smallish to large (up to 3 meters or more) primitive Late Paleozoic "mammal-like reptiles."

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.

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.

Well-known pelycosaurs include the genera Dimetrodon, Sphenacodon, Edaphosaurus, and Ophiacodon.

In 1940 the group was reviewed in detail and every species known at the time described (and many illustrated) in an important monograph by Alfred Sherwood Romer and Llewellyn Price.

Pelycosauria is a paraphyletic taxon because it excludes the therapsids. For that reason the term is not used in some modern books. Eupelycosauria is used to designate the clade that includes most Pelycosaurs along with the Therapsida and the Mammals. In contrast to "Pelycosaurs", this is monophyletic group. Caseasauria refers to a pelycosaur side-branch or clade that did not leave any descendants.

The pelycosaurs appear to have been a group of reptiles that had direct ancestral links with the mammalia, having differentiated teeth and a developing hard palate.

Dimetrodon

Dimetrodon (/daɪˈme.tɹəʊˌdɒn/) was a predatory synapsid ('mammal-like reptile') genus that flourished during the Permian Period [citation needed], living between 280 and 260 million years ago[citation needed]. It was more closely related to mammals than to true reptiles (Sauropsida), like dinosaurs, lizards and birds. [citation needed]

Dimetrodon was not a dinosaur, despite being popularly grouped with them. [citation needed] Rather, it is classified as a pelycosaur. [citation needed] It is surprisingly well-known to the general public and makes an appearance in the James Mason film Journey to the Center of the Earth. [citation needed] Fossils of Dimetrodon have been found in North America and Europe. The climate of Europe and North America in the Early Permian, was probably arid to continental, so Dimetrodon was probably adaptable. [citation needed]

Dimetrodon was a dominant carnivore, the largest known of its day. [citation needed] It grew to up to 3 meters (10 feet) in length. The name Dimetrodon means 'two-measure teeth', so named because it had a large skull with two different types of teeth (shearing teeth and sharp canine teeth),[citation needed] unlike reptiles. Dentition showing this differentiation of teeth is called heterodonty. It walked on four side-sprawling legs and had a large tail. Dimetrodon may have moved in a manner similar to present-day lizards.

The most distinctive characteristic of Dimetrodon was the spectacular sail on its back. The sail was probably used to regulate body temperature; the surface area would allow it to warm up or cool off more efficiently. In this way, it could have easily picked off slower prey that was still warming up. The sail may also have been used in mating rituals and to warn off other predators. The sail was supported by neural spines, each one sprouting from an individual vertebra. Bramwell and Fellgett (1973) calculate that a 200 kg Dimetrodon would heat up from 26° C to 32° C in 205 minutes without a sail and in only 80 minutes with a sail. [citation needed]

As a synapsid, Dimetrodon was distantly related to humans and all other modern mammals. Synapsids were the first tetrapods to evolve differentiated (or heterodont) teeth. Whereas reptiles hardly chew their food, simply gulping it down, synapsids like Dimetrodon developed teeth to help shear meat into smaller pieces for easier ingestion. These 'two-measure teeth' eventually gave rise to the various kinds of teeth present in modern mammals. For more information on human ancestry, see timeline of human evolution.

Sphenacodon

Sphenacodon was a pelycosaur that was 10 feet in length. As it name suggests, Sphenacodon belongs to the family Sphenacodontidae, a lineage that was related to Therapsids. Sphenacodon's vertebral spines were long, and probably acted as attachment points for massive back muscles, allowing the animal to lunge powerfully at its prey. Though the spines were long, it did not have a sail like Dimetrodon. However, it was closely related to Dimetrodon and other sphenacodontids. Sphenacodon lived in Early Permian in the North American region, more specifically, in Texas and New Mexico.

Edaphosaurus

Edaphosaurus (Greek: earth lizard; from edaphos, "ground"; and sauros, "lizard") was a primitive herbivorous pelycosaur reptile. Along with the Diadectidae, Edaphosaurus is one of the earliest known plant-eating animals. It had a remarkably small, short and shallow skull, a wide body and thick tail. On its back is a sail, different in shape to that of its contemporary Dimetrodon, the vertebral spines being shorter and heavier and bearing numerous small cross bars.

The earliest known species are known from fragmentary remains of small animals from latest Carboniferous. Successive species increased in size during the middle Permian period, until they attained about 3.2 metres in length, as represented by the species Edaphosaurus cruciger and Edaphosaurus pogonias. These large species are distinguished by the cervical and anterior thoracic neural spines bearing large club-like sidebars.

Edaphosaurus pogonias is also the type species, a large early Permian form whose fossils are known from the Permian red beds of Texas. However it is not known for certain if all these species attributed to this genus actually belong there. The name Naosaurus claviger is given to an earlier smaller species that is usually included under Edaphosaurus.

  • Edaphosaurus was shown in the Walking with Monsters series. In the series, it was mentioned that Edaphosaurus' worst enemy was Dimetrodon.
File:Edaphosaurus.jpg
Edaphosaurus confronting a smaller Seymouria.

Ophiacodon

Ophiacodon is a large synapsid pelycosaur. It is at least two meters in length, the largest ones were 2.5 meters, and the smaller ones were 1.5 meters. Ophiacodon 's size increases as time progresses during the Early Permian epoch until its extinction at the end of the epoch. It is a specialized member of the ophiacodontid family lineage. Being the most famous ophiacodontid in the family, its fossils were found in North America. The skull was deep, with long jaws, and provided with sharp teeth. Ophiacodon may have eaten fishes in streams and ponds, although the high narrow skull would seem to mitigate against such a lifestyle. It's related to other ophiacodontids, such as Archaeothyris, and its ophiacodontid relatives seem to be ancestral to all synapsids, including mammals.


Taxonomy and Phylogeny

  • Class Synapsida
    • ORDER PELYCOSAURIA
      • Suborder Caseasauria
        • Family Eothyrididae
          • Eothyris
        • Family Caseidae
          • Casea
          • Cotylorhynchus
          • Ennatosaurus
      • Suborder Eupelycosauria
        • Family Varanopseidae
          • Varanosaurus
          • Mycterosaurus
          • Mesenosaurus
          • Varanops
        • Family Ophiacodontidae
        • Family Edaphosauridae
        • Sphenacodontia
          • Haptodus
          • Palaeohatteria
          • Pantelosaurus
          • Cutleria
          • Sphenacodontoidea
    • ORDER THERAPSIDA

See also

  • Mammal-like reptiles

References
ISBN links support NWE through referral fees

  • Reisz, R. R., 1986, Handbuch der Paläoherpetologie – Encyclopedia of Paleoherpetology, Part 17A Pelycosauria Verlag Dr. Friedrich Pfeil, ISBN 3-89937-032-5
  • Romer, AS & Price L.I (1940), Review of the Pelycosauria. Geol. Soc. Amer. Spec. Papers 28: 1-538.
  • Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
  • Colbert, E. H., (1969), Evolution of the Vertebrates, John Wiley & Sons Inc (2nd ed.)
  • Romer, A. S., (1947, revised ed. 1966) Vertebrate Paleontology, University of Chicago Press, Chicago
  • Romer, A. S. and Price, L. I., (1940), Review of the Pelycosauria, Geological Society of American Special Papers, No 28


External links

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