Fossilized remains of Protarchaeopteryx
has gills, a mammal has hair and birds have feathers. We use these
sorts of snappy, one-off features to sort and group animals. We
take the feature for granted and don't question it further - which
is fine 99 per cent of the time. But occasionally nature reveals
an animal that defeats our superficial ways of sorting and makes
us look and think more carefully. Such a fossil animal was discovered
in China in 1997. What sort of animal do you think it is?