The only species in the proposed animal phylum Monoblastozoa (or Celomesozoa), this little bag of ciliated cells seems to be a very primitive animal with anterior and posterior openings, but it doesn’t have real tissues, and has endonuclear mythosis (on the opposite of “real” animals). The best part? Nobody knows if it really exist, or existed. Found by J. Frenzel in the saltplans of Argentina in 1892 and known only by his drawings and descriptions, it has never been found since. Forget Bigfoot, Salinella salve is much cooler.