Animals may have perfected the art of walking on land earlier than has been thought, new research suggests.
Scientists now believe efficient upright locomotion on land preceded the evolution of amniotes, the large group including reptiles, birds and mammals.
The study focused on Orobates pabsti, a large lizard-like plant-eater that lived around 290 million years ago and was thought to be closely related to amniotes.
Fossil remains of Orobates have been matched to preserved tracks, providing insights into its movement and gait.
To explore its walking style, scientists created both a digital reconstruction of the creature and a moving robot dubbed the "OroBOT".
The simulations were based on information from fossils and measurements of four living amphibian and reptile species.
The team, led by Dr John Nyakatura, from Humboldt University in Berlin, Germany, found that Orobates was probably capable of more upright walking than had been suspected.
"Our metrics indicate that Orobates exhibited more advanced locomotion than has previously been assumed for earlier tetrapods (four-legged animals), which suggests that advanced terrestrial locomotion preceded the diversification of crown amniotes," the scientists wrote in the journal Nature.
