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Temporal range: Late Carboniferous
Archaeothyris BW.jpg
Life restoration of Archaeothyris
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Family: Ophiacodontidae
Genus: Archaeothyris
Reisz, 1972
Type species
Archaeothyris florensis
Reisz, 1972

Archaeothyris is an extinct genus of ophiacodontid synapsid that lived during the Late Carboniferous and is known from Nova Scotia. Dated to 306 million years ago, Archaeothyris, along with a more poorly known synapsid called Echinerpeton, are the oldest undisputed synapsids known.[1] (Protoclepsydrops is slightly older, but its status as a synapsid is unclear as the remains are more fragmentary). Fossils of Archaeothyris were first described in 1972 from the Joggins fossil cliffs, the same locality in which the early reptiles Hylonomus and Petrolacosaurus (both of which resemble Archaeothyris) were found.


Archaeothyris belonged to the family Ophiacodontidae, a group of early pelycosaurs that evolved early in the Late Carboniferous. It was one of the earliest and most basal synapsids (the group which include mammals).

Appearance and lifestyle[edit]

Unlike Hylonomus and its kin, Archaeothyris was relatively large, measuring 50 centimetres (20 in) head to tail. It was also more advanced than the early sauropsids, having strong jaws that could open wider than those of the early reptiles. While its sharp teeth were all of the same shape, it did possess a pair of enlarged canines, suggesting that it was a carnivore.[2]

Archaeothyris lived in what is now Nova Scotia, about 306 million years ago in the Carboniferous Period (Pennsylvanian).[3] Nova Scotia at this time was a swamp, similar to today's Everglades in Florida. The "trees" (actually giant club mosses) were very tall, some, such as Lepidodendron, up to 50 metres (164 ft) tall. Archaeothyris and the other early amniotes dwelled on the forest ground.

See also[edit]


  1. ^ Falcon-Lang, H.J., Benton, M.J. & Stimson, M. (2007): Ecology of early reptiles inferred from Lower Pennsylvanian trackways. Journal of the Geological Society, London, 164; no. 6; pp 1113-1118. article
  2. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 186. ISBN 1-84028-152-9. 
  3. ^ Hess J.C., Lippolt H.J. (1986): 40Ar/39Ar ages of tonstein and tuff sanidines: new calibration points for the improvement of the Upper Carboniferous time scale. Chem Geol no 59: pp 143–154
  • Kemp, T. S. (2005). The Origin & Evolution of Mammals. Oxford: Oxford University Press. ISBN 0-19-850761-5. 

External links[edit]