Diplodocus stripped branches at feeding time

16 July 2012

Diplodocus combed and raked leaves from branches rather than stripping them of bark scientists have uncovered, using techniques traditionally reserved for designing F1 cars and aeroplanes.

CT scan images of a Diplodocus skull showing 3 feeding scenarios

CT scan images of a Diplodocus skull showing 3 feeding scenarios, a. is normal biting, b. is stripping branches of leaves and c. is stripping bark. Red, orange, yellow, green, then light blue indicate the greater stress.

A team of scientists, including those at the Natural History Museum and University of Bristol, replicated the stresses and strains a Diplodocus skull and teeth would have experienced during 3 feeding scenarios, one for biting normally, one for stripping branches of their leaves, and one for stripping bark.

They used CT scans to create a 3D model of a complete Diplodocus skull. The model was then biomechanically analysed to test the different scenarios, using finite element analysis (FEA), a technique widely used for designing everything from aeroplanes to orthopaedic implants.

Diplodocus lived 150 million years ago and weighed about 20-25 tonnes. Evidence shows Diplodocus was a herbivore, but there has been much discussion about exactly how, with its unusual shaped head and teeth, it would have eaten enough vegetation. 

The new research showed Diplodocus' skull received stress around the teeth and below the eye socket during normal vertical biting and stripping leaves from branches. However this stress wasn't enough to be unsafe for the bone. 

They team says the teeth were used to grip rather than shear through vegetation, which would then be detached from the plant by pulling away or rotating the head, like a modern-day giraffe for instance.

The bark stripping scenario, however, produced much more stress in the same areas, especially around the teeth. These bones would not have been able to withstand the forces applied when stripping bark from trees.

'Using these techniques, borrowed from the worlds of engineering and medicine, we can start to examine the feeding behaviour of this long extinct animal in levels of detail that were simply impossible until recently,' says Dr Paul Barrett, dinosaur expert at the Museum.

Dr Mark Young at the University of Bristol says, 'Sauropod dinosaurs, like Diplodocus, were so weird and different from living animals there is no animal we can compare them with. This makes understanding their feeding ecology very difficult. That’s why biomechanical modelling is so important to our understanding of long-extinct animals'.

The team conclude that the unusual skull shape of Diplodocus may have been an adaptation for food procurement and not simply a response to resisting bite forces. So, Diplodocus' unusual skull may have evolved for getting food rather than munching it.

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