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Environments and Behaviour.

Most forms of Nectrideans were exclusively aquatic. They formed an important part of the coal-swamp faunas of North America and Europe that were thriving 300 million years ago.

Some specimens of Diplocaulus have been found within red shales and sandstones. These have been interpreted as having formed in a deltaic, monsoonal environment (Cruickshank & Skews 1980). Associated fauna have included fresh-water sharks and other Carboniferous-Permian amphibians such as microsaurs, cotylosaurs and pelycosaurs.

Diploceraspis is associated with pond or lake deposits.

The mode of locomotion used by most Nectrideans is described as anguilliform swimming. Their long deep tails were used to swim while the short trunks were held rigid. Swimming was through sinusoidal flexure of the body, a side to side motion seen in modern newts. The construction of the vertebrae was uniquely adapted for lateral bending. Limbs probably only had a supplementary role. The horizontal zygapophyses prevented dorso-ventral flexion and precluded torsion (twisting) of the vertebral column. In long species the oscillations due to anguilliform swimming were not marked. While adaptations in the skull and pectoral girdle of a short-trunked genera, such as Keraterpeton, in the form of extra ligamentous connections, enabled the oscillations to be dampened.

In comparison though one genera, Diceratosaurus, appears to have swum by paddling its hind legs.

Scincosaurus appears to have been adapted to a terrestrial (or seasonally aqautic) existence, living in the carboniferous “leaf-litter” where it pushed its way under litter, stones or logs. Short limbs and small feet indicate it was not a runner and unlikely to have dwelt on the surface.

A shallow swimming trackway

Figure 7. Fossilised trackway. A, Batrachichnus delicatlulus from New Mexico, amphibian swimming trackway. B, Interpretive drawing, including tentative reconstruction of producer; scale bar represents 10mm (with permission from Braddy et al. 2003).

A fossilised tackway has been identified from the Lower Permian of southern New Mexico and is interpreted as a small amphibian (perhaps a Nectridean) swimming in shallow water in a similar manner to the motion of a side-winder snake (Braddy et al. 2003).

Nectrideans were probably the prey of pleuracanth sharks and crossopterygian fish as well as a suite of other carnivores (Cruickshank & Skews 1980).

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

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