Westlothiana

Westlothiana lizziae is an early tetrapod. It is a transitional fossil, with a mixture of amphibian and early amniote characters.282 Its body shape had a superficial resemblance to modern-day lizards. It lived during the Carboniferous period, about 350 million years ago. 

The type specimen was discovered in East Kirkton Quarry, Bathgate, Scotland, in 1984. It was named after the County of West Lothian where it was found.Smithson T.R. & Rolfe W.D.I. 1990. Westlothiana gen. nov.: naming the earliest known reptile. Scottish Journal of Geology 26, 137–138. 

 Westlothiania in life 
This species probably lived near a freshwater lake, probably hunting for other small creatures that lived in the same habitat. It was a slender animal, with rather small legs and a long tail. 

Together with Casineria, another transitional fossil found in Scotland, it is one of the smallest terapods known, being a mere 20 cm in adult length. 

The small size has made it a key fossil in the search for the earliest amniote, as amniote eggs are thought to have evolved in very small animals.Carroll R.L. 1991. The origin of reptiles. In: Schultze H.-P. & Trueb L. (eds) Origins of the higher groups of tetrapods — controversy and consensus. Ithaca: Cornell University Press. 331-353Laurin M. 2004. The evolution of body size, Cope's Rule and the origin of Amniotes. Systematic Biology 53 (4): 594-622. doi: 10.1080/10635150490445706 article There are derived (advanced) features which tie it in with the amniotes rather than amphibians. These are: unfused ankle bones, lack of labyrinthodont infolding of the dentine in teeth, a lack of an otic notch and a generally small skull.Paton R.L; Smithson T.R. & Clack, J.A. 1999. An amniote-like skeleton from the early Carboniferous of Scotland. Nature 398: 508–513

The long body and small legs were a possible adaptation to burrowing, similar to that seen in modern skinks.Ruta M.; Coates M.I. & Quicke D.L.J. 2003. Early tetrapod relationships revisited. Biological Review 78: 251-345.PDF 

 Phylogeny 
Ideas of how Westlothiana should be classified has varied from basal amniote to an amphibian Lepospondyl. The actual phylogenetic position of Westlothiania is uncertain.

Other websites
Westlothiana lizziae from the Viséan of East Kirkton, West Lothian, Scotland, and the amniote stem

References

Category:Stem tetrapods