wylie brys was digging with his dad tim brys , back in september at a construction site near a mansfield , texas , grocery store when he made the ancient discovery .
` he walked up ahead of me and found a piece of bone , ' dallas zookeeper brys said .
` it was a pretty good size and i knew i had something interesting .
' the pair had been finding fish vertebrae , but when wylie came back with the bone , brys asked him to take him to where he found it .