No, really, sea spiders:

Weird spider-like creatures that live at the bottom of the ocean and use a 'straw' to suck on their prey are baffling scientists.

These sea spiders, some of which are blind, are defying scientific classification.

Marine zoologist Dr Claudia Arango of the Australian Museum in Sydney agrees they are arthropods, but which type?

Article includes cReEpY pictures of the little monsters.