Siboglinidae, also known as the beard worms,'s a family of polychaete annelid worms whose members made up the former phyla Pogonophora (the giant tube worms) and Vestimentifera. They're composed of about 100 species of vermiform creatures and live in thin tubes buried in sediments at ocean depths from 100 to 10,000 m. They can also be found in association with hydrothermal vents, methane seeps, with sunken plant material or whale carcasses. Anatomy Most are less than 1 mm in diameter but 10 to… (More on Siboglinidae)