Archaeothyris

Archaeothyris was one of the earliest definite synapsids. It lived in the late Carboniferous period, 306 million years ago.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, #6. 1113-1118  

It shares this fame with another species (Echinerpeton) about which little is known. Protoclepsydrops is even slightly older, but only fragments have been found.

Archaeothyris was found in Nova Scotia, in the same area as several other species which were probably sauropsids: Hylonomus, and Petrolacosaurus. 

Archaeothyris belonged to a group of early pelycosaurs which evolved early in the Pennsylvanian. It is thus seen as the precursor of all synapsids (which include mammals).

 Appearance and lifestyle 
Unlike the early sauropsids, Hylonomus and its kin, Archaeothyris was relatively large, measuring  head to tail. It was also more advanced than the early sauropsids (~reptiles), with strong jaws that could open wider than those of the sauropsids. Its sharp teeth were all of the same shape, and it had a pair of enlarged canines, suggesting that it was a carnivore.

Archaeothyris lived in what is now Nova Scotia, about 306 million years ago in the Carboniferous Period (Pennsylvanian).Hess J.C & Lippolt H.J. 1986. 40Ar/39Ar ages: new calibration points for the improvement of the Upper Carboniferous time scale. Chem Geol 59: pp 143–154 Nova Scotia was at this time a swamp, similar to today's Everglades in Florida. The 'trees' (actually giant clubmosses) were very tall. Some, such as Lepidodendron, were up to  tall. Archaeothyris and the other early amniotes lived on the forest floor.

References

Category:Synapsids
Category:Stem tetrapods