Limnognathia maerski is a microscopic acoelomate freshwater animal, discovered living in cold springs on Disko Island, Greenland, in 1994.

[1] Since then, it has also been found on the Crozet Islands of Antarctica[2] as well as in the British Isles,[3] suggesting a worldwide distribution, although there are likely different species yet to be described.

L. maerski has a large ganglion, or 'brain', in its head, and paired nerve cords extending ventrally (along the lower side of the body) towards the tail.

Flexible cilia are arranged in a horseshoe-shaped area on the forehead, and in spots on the sides of the head and in two rows on the underside of the body.

The cilia on the forehead create a current that moves food particles towards the mouth.