Amelia Matthews, of Tikipunga Primary School, asks :-
How do people know the bones they find are dinosaur bones and not that of some other large animal?
Joan Wiffen, a New Zealand amateur with an international reputation as a finder of dinosaur bones, responded.
Dinosaurs died out (became extinct) 65 million years ago, so that the bones can only be found in sediments which are geologically dated 65 million years old, or older. These are bones from dinosaurs which died and were buried rapidly and where conditions were right for them to be preserved in those sediments and become fossils. The age of rocks in your area can be found by purchasing a geological map of your district. If they are younger than Late Cretaceous, that is 65 million years old - you are unlikely to find dinosaurs!
The people who hunt for dinosaur bones also study the skeleton, that is the hard parts of dinosaurs, so that they learn to distinguish dinosaur bones from bones of other animals. Most bones found laying in paddocks, on river beds or beaches in New Zealand are from dead farm animals. Any bones found in road cuttings, river or coastal cliffs or imbedded in rock may be fossilised and are worth recording by drawings, photos, and the date and place where they were found, and reported to the nearest museum but they are unlikely to be dinosaur bones unless the rocks there are the right age.
When we find fossil bones that we believe may be dinosaurian, the rocks are brought home and the fossils carefully examined. The bones are photographed, and measured then comparisons of these bones are made with other dinosaurs, in our dinosaur books. If we dont know what they are, then photos, and if necessary casts of the bones, are sent to experts overseas for comparison with dinosaur bones of similar age in other parts of the world. It is only after this has been done and numerous dinosaur experts have been asked for their opinions that any attempt at identification is made.