What was the first dinosaur bone to be found?

In Cornwall, Oxfordshire a distal end of a femur is the first dinosaur bone as described in 1677 by Robert Plot of the Ashmolean Museum. He called it the thigh bone of a human giant. In 1772 the bone was relabeled as Scrotum Humanum and 1824 it was re-labeled a Megalosaurus bone by William Buckland.