Part of a fossilized skeleton of a plesiosaur. The slightly lustrous quality of the 'bones' shows that they have been opalized - the original bone material replaced with opal (hydrous silicon oxide) to form the permanent fossil. The fossil is about 120 million years old, and was found in Australia. The plesiosaur was a marine carnivorous dinosaur that thrived in the mid to late Cretaceous Period. Photographed at a duty-free shop in Sydney, Australia. .