Certain additional small groups should probably be recognized as independent lines of descent or phyla, but their relationships are obscure - they are the Mesozoa, the Polyzoa, the Acanthocephala and the Gastrotricha.
Gastrotricha.
Gastrotricha (q.v.).
GASTROTRICHA, a small group of fairly uniform animals which live among Rotifers and Protozoa at the bottom of ponds and marshes, hiding amongst the recesses of the algae and sphagnum and other fresh-water plants and eating organic debris and Infusoria.