Dimetrodon

Dimetrodon Temporal range: Cisuralian to Guadalupian (Asselian to Roadian),
Skeleton of D. limbatus, Staatliches Museum für Naturkunde Karlsruhe
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Family:	†Sphenacodontidae
Subfamily:	†Sphenacodontinae
Genus:	†Dimetrodon Cope, 1878
Type species
†Dimetrodon limbatus Cope, 1877
Species
See below
Synonyms
Genus synonymy Bathygnathus Leidy, 1854 Embolophorus Cope, 1878 Theropleura Cope, 1880 Bathyglyptus Case, 1911 Eosyodon Olson, 1962 Species synonymy Bathygnathus borealis Leidy, 1854 Clepsydrops limbatus Cope, 1877 Clepsydrops gigas Cope, 1878 Clepsydrops natalis Cope, 1878 Dimetrodon gigas Cope, 1878 Dimetrodon incisivus Cope, 1878 Dimetrodon rectiformis Cope, 1878 Embolophorus dollovianus Cope, 1878 Dimetrodon semiradicatus Cope, 1881 Clepsydrops macrospondylus Cope 1884 Dimetrodon platycentrus Case, 1907 Theropleura grandis Case, 1907 Bathyglyptus theodori Case, 1911 Dimetrodon maximus Romer, 1936 Eosyodon hudsoni Olson, 1962

Another species, showing the skull openings typical of a synapsid

Dimetrodon was a genus of non-reptilian Pelycosaur (early Synapsida) from the first part of the Early Permian period (about 295–272 million years ago).

Fossils

Dimetrodon walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the southwestern United States, from red beds in Texas and Oklahoma. Newly discovered fossils of Dimetrodon are now found in Germany. The largest known species of Dimetrodon is D. angelensis at 4.6 metres (15 ft) and the smallest is D. teutonis at 60 centimetres (24 in).

Ecosystem

Dimetrodon was a carnivore, probably the top predator in its environment. Its main feature is the large sail on its back formed by elongated spines extending upwards from the vertebrae. The spines would be joined by skin. The general opinion of paleontologists is that it was a temperature-regulating device. The idea is that the animal could warm up in the early morning by placing itself broadside to the Sun, and later could cool off in the shade, or arrange for its body to get less sunlight. At this stage in evolution, no land animals were homoiotherms. Very likely the sail was also used for sexual or territorial signalling. In which case, the skin would be coloured. This, of course, is supposition, but it does make sense of the animal's most extraordinary feature.

Evolutionary terms

In evolutionary terms, Dimetrodon was a synapsid (Primitive mammal), a line of land animals which eventually gave rise to the mammals. It was not on the direct line of descent, but a good example of the evolutionary grade typical of Permian synapsids. Dimetrodon evolved from lizard like syanspids from the Late Carboniferous.

Pelycosaur cousin

Another synaspid was the smaller and similar Edaphosaurus. Edaphosaurus was an herbivore and probably the prey item for Dimetrodon.

Growth and metabolism

Dimetrodon probably had a much higher metabolism than its cousin (Edaphosaurus). While Dimetrodon was faster, Edaphosaurus was probably really slow. This indicated that Edaphosaurus was cold-blooded. By using its sail and trapping heat from the sun, Edaphosaurus could use this way as regulating its own body temperature. Same with Dimetrodon.

Skull

In the front of Dimetrodon's mouth was steak like biting teeth (front teeth). But in the back of it's mouth were teeth that were like chewing teeth. This told us that Dimetrodon had different pairs of teeth.