Westlothiana
Westlothiana lizziae is an early tetrapod. It is a transitional fossil, with a mixture of amphibian and early amniote characters.[1]282 Its body shape had a superficial resemblance to modern-day lizards. It lived during the Carboniferous period, about 350 million years ago.
| Westlothiana Temporal range: early Carboniferous
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| Westlothiana lizziae | |
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| Genus: | Westlothiana
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| Species: | W. lizziae
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| Binomial name | |
| Westlothiana lizziae Smithson and Rolfe, 1990
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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.[2]
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.[3][4] 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.[5]
The long body and small legs were a possible adaptation to burrowing, similar to that seen in modern skinks.[1]
Phylogeny
Ideas of how Westlothiana should be classified has varied from basal amniote to an amphibian Lepospondyl.[6][2] The actual phylogenetic position of Westlothiania is uncertain.[4]
Westlothiana Media
Size comparison of Westlothiana lizziaea. Based on skeletal from Smithson et al. (1993).
A color-coded diagram of the skull of Westlothiana lizziae
A collection of schematic diagrams showing the arrangement of ankle bones in Westlothiana and other tetrapods. For Westlothiana, a) applies to Smithson (1989)'s interpretation and b) applies to Smithson et al. (1993)'s
Other websites
References
- ↑ 1.0 1.1 Ruta M.; Coates M.I. & Quicke D.L.J. 2003. Early tetrapod relationships revisited. Biological Review 78: 251-345.PDF Archived 2008-05-22 at the Wayback Machine
- ↑ 2.0 2.1 Smithson T.R. & Rolfe W.D.I. 1990. Westlothiana gen. nov.: naming the earliest known reptile. Scottish Journal of Geology 26, 137–138.
- ↑ 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. 331-353
- ↑ 4.0 4.1 Laurin 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
- ↑ Paton R.L; Smithson T.R. & Clack, J.A. 1999. An amniote-like skeleton from the early Carboniferous of Scotland. Nature 398: 508–513
- ↑ Palmer, D., ed. (1999). The Marshall illustrated encyclopedia of dinosaurs and prehistoric animals. London: Marshall Editions. p. 62. ISBN 1-84028-152-9.