Westlothiana

Westlothiana
Temporal range: Viséan, 338 Ma
↓
Type specimen of Westlothiana lizziae
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: incertae sedis
Order: Cotylosauria?
Genus: Westlothiana
Species: W. lizziae
Binomial name
Westlothiana lizziae
Smithson and Rolfe, 1990

Westlothiana is a genus of reptile-like amphibian or possibly early reptile that bore a superficial resemblance to modern-day lizards. It lived about 338 million years ago during the latest part of the Visean age of the Carboniferous period. The name Westlothiana means "Animal from West Lothian". It is known from a single species, Westlothiana lizziae. The type specimen was discovered in East Kirkton Quarry, West Lothian, Scotland in 1984. Westlothiana's anatomy contained a mixture of both labyrinthodont and reptilian features, and was originally regarded as the first reptile.[1] Most scientists place them among the Reptilomorpha, as a sister group to the first amniotes.[2][3]

Paleobiology

Restoration

This species probably lived near a freshwater lake, and probably hunted 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 reptile-like amphibians 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.[4][5] Advanced features that tie it in with the reptilian rather than amphibian group include unfused ankle bones, lack of labyrinthodont infolding of the dentin, the lack of an otic notch, and a generally small skull.[6]

Ruta & al. (2003) interpreted the long body and small legs as a possible adaption to burrowing, similar to that seen in modern skinks.[2]

Phylogeny

The phylogenetic placement of Westlothiana has varied from basal amniote (i.e. a primitive reptile) to a basal Lepospondyl, in an analysis with the lepospondyls branching off from within Reptiliomorpha.[1][3] The actual phyllogenetic position of Westlothiana is uncertain, reflecting both the fragmentary nature of the find and the uncertainty of labyrinthodont phylogeny in general.[5]

Name

Westlothiana was named after the eponymous county in Scotland. When first found by professional fossil hunter Stan Wood, this creature was nicknamed 'Lizzy the Lizard'. This eventually found its Latinised way into the species names as lizziae.

References

  1. 1 2 Smithson, T.R. & Rolfe, W.D.I. (1990): Westlothiana gen. nov. :naming the earliest known reptile. Scottish Journal of Geology no 26, pp 137–138.
  2. 1 2 Ruta, M.; Coates, M.I. & Quicke, D.L.J. (2003): Early tetrapod relationships revisited. Biological Review no 78: pp 251-345.PDF
  3. 1 2 Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 62. ISBN 1-84028-152-9.
  4. ↑ Carroll R.L. (1991): The origin of reptiles. In: Schultze H.-P., Trueb L., (ed) Origins of the higher groups of tetrapods — controversy and consensus. Ithaca: Cornell University Press, pp 331-353.
  5. 1 2 Laurin, M. (2004): The Evolution of Body Size, Cope's Rule and the Origin of Amniotes. Systematic Biology no 53 (4): pp 594-622. doi:10.1080/10635150490445706 article
  6. ↑ Paton R.L., Smithson, T.R. & Clack, J.A. (1999): An amniote-like skeleton from the Early Carboniferous of Scotland. Nature no 398: pp 508–513
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