Cryptozoology – a strange word for a strange science. Let's face it, any discipline which includes the study of everything from the Loch Ness monster, a fur-lined trout and millions of species of nematode worms is nothing if not eclectic.This science of finding as-yet-unknown creatures covers a broad area. It ranges from the sea monsters and chimera that most of the scientific community would dismiss, to the millions of creatures that we know do exist but have just never been seen or described by science.Dr Geoff Swinney is the curator of lower vertebrates, fish, amphibians and reptiles at the National Museums of Scotland. His is also their resident cryptozoologist, looking after those animals that – as he says, "one day might be". His broad remit covers everything from new species of bats to taxidermy hoaxes. "It's all a spectrum," says Swinney. "At one end are animals who have not been described by the scientific community and at the other end we have things like this constructed mermaid."With that Swinney takes down a glass case from a shelf in the small neon-lit underground room where he keeps his cryptozoological specimens. What he places on the table is strange and grotesque. A small mermaid creature, vertebrae notched along the back and adorned with an ancient leathery head, in which is a set of teeth more ferocious than your average Alsatians.These creatures turned up in the 19th century and caused a sensation. When Barnum, the circus pioneer, displayed his feejee mermaid the crowds went wild. No-one then considered it to be a fake, yet Swinney explains that's exactly what it was."It's a real fish, a rass, the head is modelled from papier mâché or something, and then the teeth belong to the rass."The fact that it's a fake doesn't make it any less interesting for science. Swinney believes that there might be more to these mermaids than a taxidermist's joke to fool the gullible.