ISLAMABAD         -        Some 313 million years ago, two creatures trekked across sand dunes in what is now the Grand Canyon and now paleontologist have uncovered evidence of their journey. A massive boulder fell from the Mankacha Formation during a collapse and imprinted in the red stone are two pairs of the oldest recorded vertebrate tracks. Researchers say the footprints belonged to four-legged shelled-egg-laying animals and reveal such animals traveled up sand dunes eight million years earlier than previously believed. The newly discovered tracks record the passage of two separate creatures of the same species walking a few hours or days apart from each other. One pair of tracks consists of 28 imprints with claws in each impression while the other set suggests the animal may have had an injured right foot - as there were no claw marks present on that side. The ‘surprising discovery’ was made by Norwegian geology professor Allan Krill, who was hiking with his students through the canyon.