Giant sauropods walked more like hippos than elephants

A new study led by Liverpool John Moores University (LJMU) has found that giant, long-necked sauropod dinosaurs such as diplodocus had a gait that was most similar to that of a hippopotamus. In this so-called “diagonal gait,” each step of a front leg is in tandem, or very closely followed by, the hind leg from the opposite side.

Such a gait allowed for efficient walking while maintaining diagonal limb support throughout the step cycle, which was very important for these huge, wide-gauged creatures.

The sauropods – a group of herbivorous dinosaurs that lived between 200 million and 66 million years ago – were among the largest animals to have ever walked the Earth, some of them weighing the equivalent of 14 African elephants. Scientists have previously thought that these creatures used to walk like elephants, employing a “lateral gait,” with the two limbs on the same body side tending to move forward one after the other.

“Everybody always assumed that sauropods walked like modern elephants,” said study lead author Jens Lallensack, a paleontologist at LJMU. “But they didn’t, and we think that’s because the sauropods were just so much broader.”

Four-footed animals use different gaits, such as trots, walks, or pace gaits. In a trot, one diagonal pair limb – such as the hind right and front left legs – moves together, followed by the other diagonal limb pair. A large number of mammals use trots while running, while reptiles use this type of gait at slow speeds.

By analyzing fossilized Lower Cretaceous sauropod footprints from three sites in Arkansas, Dr. Lallensack and his colleagues have found that the sauropod gait was most similar to a trot, while still presenting slight differences. 

When most animals trot, the two diagonal limbs land at the same time. In the case of sauropods though, the front foot touched down just before the hind, diagonal one. This particular gait allowed them to have at least one foot on the ground on both the left and right sides of the body at all times, preventing them to sway from side to side and lose their balance. 

“Sauropods chose a gait that maximized stability, but still allowed for efficient walking,” concluded Dr. Lallensack.

The study is published in the journal Current Biology. 

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By Andrei Ionescu, Earth.com Staff Writer