New study suggests explanations for usage of plesiosaurs’ long necks

Plesiosaurs are an extinct group of marine reptiles from the age of dinosaurs who are famous for their long necks. The effect of such long necks on how these animals swam is a mystery but now computer simulations are helping LJMU scientists understand what would happen if a plesiosaur turned its head while swimming.

The necks of some plesiosaurs could reach up to 11m, over two-thirds of the total length of the animal. To understand the effects of this elongated neck on swimming performance, Dr Pernille V. Troelsen and colleagues from LJMU used computer modelling – a method called Computational Fluid Dynamics - to simulate the flow of water around plesiosaurs with different sized necks, and with the neck straight or turned.

Dr Troelsen and researchers showed that making the neck thicker reduced the drag on the animal by allowing the water to flow more smoothly over the neck and body.

She commented: “It seems the long neck wasn’t a disadvantage when these animals were swimming forwards. Increasing the length of the neck had no noticeable effect when it was straight, but if the plesiosaur had turned its head, perhaps to catch food, those with longer necks would have experienced a much greater drag force slowing them down and putting pressure on the neck. Some plesiosaurs might have hunted for food similarly to sea lions.”

Soft-tissue outlines are very rarely preserved in the fossil record, and so it is difficult to know what these long-extinct animals truly looked like. But the simulations would imply that if these animals were active swimmers, they may have had thicker necks than previously thought.

The research paper, entitled ‘Functional morphology and hydrodynamics of plesiosaur necks: Does size matter?’ was published in the Journal of Vertebrate Paleontology, and the work formed a core part of Troelsen’s PhD thesis.

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