Often people working 70 years ago or more had different ideas of what constituted a new species - maybe they didn't recognise things that we would as being distinct, or they might not have had access to technologies, such as being able to extract and sequence DNA."
But there is no central museum database and scientists have little idea of what each collection contains. Many organisations are now putting their inventories online, and Dr Norris says that will make research faster and more accessible.