Dimetrodon

extinct genus of synapsids

Dimetrodon was a pelycosaur (early Synapsida) from the first part of the Permian period (about 295–272 million years ago).

Dimetrodon
Temporal range: Cisuralian to Guadalupian (Asselian to Roadian), 295–270 Ma
Skeleton of D. limbatus, Staatliches Museum für Naturkunde Karlsruhe
Scientific classification Edit this 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 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. 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).[1][2]

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 palaeontologists is that it was a temperature-regulating device.[3] 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.

In evolutionary terms, Dimetrodon was a synapsid, a line of land animals which eventually gave rise to the mammals. It was not on the direct line of descent,[4] but a good example of the evolutionary grade typical of Permian synapsids.

References

change
  1. "The Kungurian Age". Palaeos. Archived from the original on 12 November 2013. Retrieved 29 September 2013.
  2. Fröbisch J. et al 2011 (2011). "A new basal sphenacodontid synapsid from the Late Carboniferous of the Saar-Nahe Basin, Germany". Acta Palaeontologica Polonica. 56 (1): 113–120. doi:10.4202/app.2010.0039. S2CID 45410472.{{cite journal}}: CS1 maint: numeric names: authors list (link) [1]
  3. Florides G.A. et al 2001. Natural environment and thermal behaviour of Dimetrodon limbatus. Journal of Thermal Biology 26 (1): 15–20. [2]
  4. Benson R.J. 2012. Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies. Journal of Systematic Paleontology 10 (2). [3]