A family of sedentary marine worms (known as beard worms) that live in all the world's oceans, generally at depths between 330 and 13,200 ft (100 and 4000 m), shallower at higher latitudes and deeper in trenches. The first specimens of the Pogonophora, previously considered to be a phylum, but now known more accurately as Siboglinidae (a family of polychaete annelids), were dredged up late in the nineteenth century, but first investigated in the 1950s by the Russian zoologist A. V. Ivanov. Siboglinids construct a chitinous tube and have no mouth, gut, or anus in their postembryonic anatomy. Instead of actively feeding, they derive their nutrition from symbiotic bacteria hosted in specialized tissues or via absorption. With new technologies in deep-sea exploration, such as crewed and remotely operated submersibles, many new species of Siboglinidae have been discovered in unexpected habitats over the past three decades, notably around hydrothermal vents and cold-water hydrocarbon seeps, and on decaying whale bones.