Pogonophora, an animal phylum restricted to the deep sea and remarkably common in certain habitats there. About 80 pogonophoran species are known today, with new species still being discovered. One of the most spectacular zoological discoveries was the finding in 1977 of giant pogonophoran worms, 1.5 meters long, growing in heated, sulfur rich water around warm-water vents in the Pacific Ocean, 2600 meters below the surface. These worms are sometimes placed in their own phylum, the Vestimentifera, but they are similar to pogonophorans in most respects, and the current tendency is to group these rift-dwelling worms together with the rest of the Pogonophora into one phylum. The name Pogonophora is Greek for "beard-bearers," and comes from the fact that many species have from one to many tentacles at the anterior end.