When is a worm not a worm? When it's a jellyfish, of course:
The worm, Buddenbrockia, has been seen only a handful of times since its discovery in 1851 and exactly where it fits in the animal kingdom has long puzzled scientists. ‘It has no mouth, no gut, no brain and no nerve cord,’ said Professor Peter Holland of Oxford University’s Department of Zoology who led the study. ‘It doesn’t have a left or right side or a top or bottom – we can’t even tell which end is the front!’
Genetic sequencing has shown that it is not a worm at all, but instead a relative of the anemones and jellyfish.