Real life dune worms
Eunice aphroditois is a polychaete worm which is sort of like a dune sandworm, except maybe not quite as big and they live in marine habitats. Their appearance is, if anything, a little more bizarre.
These worms will hide under the sand of aquatic environments with only a thin antennae sticking out. When an appropriate prey item brushes past they launch out at terrific speeds and move in for the kill. Apparently those razor sharp teeth can saw some animals clean in half. Their jays are made up of 1 pair of mandibles (the large arched structure) and 4-6 pairs of maxillae (the 'teeth'). If they are Hungary enough they may go looking for food instead of waiting around for it to come to them. Despite their obvious coolness, very little is known about them. It is believed that they use some sort of poison to kill or disable their prey as they are capable of taking down prey that is larger than themselves. This poison, if it exists, has not been identified. The rainbow colouration is... well I don't know why they are rainbow coloured, and I can imagine why seeing as they spend almost all their time underground and are probably broadcast spanners so they don't need to impress a mate.
So how much smaller than a dune sandworm are they? Well you are probably thinking that they are maybe 10 or 20 cm long, but they can grow up to 3 m long. Yep that is bigger than you. Before you ask, no there have not been any recorded human deaths by Bobbit worm, probably because they prefer to live at leat 10m under the surface of the water. Having said that, it would make a good crazy theory for what happened to Harold Holt.
And here is a video of the Bobbit worm in action:
Eunice aphroditois is found in warm ocean environments all over the world.
Experts seem to think that the classification is a bit tentative at this stage but it currently runs like this:
Species: Eunice aphroditois