ENGINEERINGNET.EU -- Instead, the researchers think the animal, which scientists call an early tetrapod, simply hauled itself out of the primordial ooze with its two front limbs, using its back limbs merely for balance.
"These early tetrapods probably moved in a similar way to living mudskipper fishes in which the front fins, or arms, are used like crutches to haul the body up and forward," explains Dr Stephanie Pierce from The Royal Veterinary College and University of Cambridge, lead author of the study, published in Nature.
Pierce and co-authors, Professor Jennifer Clack from the University of Cambridge and Professor John Hutchinson form The Royal Veterinary College, made their discovery by creating the first ever 3D computer model of an early tetrapod’s skeleton. Their aim was to work out how its limbs might have moved.
They scanned dozens of fossil specimens of a tetrapod that lived around 360 million years ago called Ichthyostega. They digitally separated the bones from the rock surrounding the fossils.
Then they put each bone back together into a whole skeleton, ‘ like a jigsaw puzzle,’ using animation software, before carefully manipulating the model to estimate each joint’s range of motion.
To make sure their computer model was reliable, they built similar models of seals, salamanders, platypuses, crocodiles and otters and used the model to test their joint movements. They found that the model predicted a reliable amount of mobility.
The findings suggest that some of the 400 million-year-old footprints discovered in Poland two years ago - thought to have been made by similar tetrapods - may have been made by altogether different four-legged animals.
The study was funded by the Natural Environment Research Council.
BACKGROUND
'Three-dimensional limb joint mobility in the early tetrapod Ichthyostega', by Stephanie E Pierce, Jennifer A Clack and John R Hutchinson, was published in Nature on 23 May 2012.
