We still have the problem of the ctenophores. "Comb jellies", they used to be, until it turned out they have practically nothing in common with jellyfish except transparency and radial symmetry. Or with anything else.<p>They use proteins similar to those used by other animals, but for different things. Some people think they evolved muscles and nerves entirely independently of other animals. Some people think they fell from the sky.<p>Whatever you think, they are astonishing in every detail. Watch videos of Beroe if you have any doubts.