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The Fossil Record.

Origins and Early Forms.

The earliest occurrence of the Nectridean order occur during the period known as the Westphalian A (in Europe) or the Lower Pennsylvanian (in North American). This was approximately 315 million years ago. Even these early specimens are part of an already diverse and specialised group. This observed diversification suggests an origin in the Lower Carboniferous (350 million years ago).

The two earliest forms are considered to be Arizonerpeton wellsi and Urocordylus wandesfordii. Both come from the middle-Carboniferous (around 315 million years ago). Earlier species may yet be found. 

Even though Scincosauridae occur within the mid-ranges of the distribution for all Nectridean species, their lack of cranial specialisations means they may reflect the primitive condition of the order (Bossy & Milner 1998).

Occurrences; where and when.

Nectridean remains where first discovered at Jarrow Colliery, Killkenny, Ireland, in 1864. Since then they have been found in France, the Czech Republic, England, throughout North America and in Morocco.

Geographical distribution of Nectridean fossils.

Figure 8. Geographical distribution of Nectridean fossils.

The earliest Nectridean forms are found in the middle-Carboniferous. The last Nectrideans are found during the late Guadalupian. This does not mean that no species existed after this time, just that none have yet to be found! For more information about the fate of the Nectrideans see also the Modern Forms section.

Temporal distribution of Nectridean fossils.

Figure 9. Temporal distribution of Nectridean fossils.

Back to the Nectridean index.
Major Subgroups of the Nectrideans.
Anatomy and Behaviour.
Modern Forms.
Literature and Web Links.

Author: Iain McIntyre
Last updated: 19/11/2006
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