They can also be found in association with hydrothermal vents, methane seeps, sunken plant material, and whale carcasses.

The anterior end is called the cephalic lobe, which ranges from one to over 200 thin branchial ciliated tentacles, each with tiny side branches known as pinnules.

The main part of the body is the trunk, which is greatly elongated and bears various annuli, papillae, and ciliary tracts.

Posterior to the trunk is the short metamerically segmented opisthosoma, bearing external paired chaetae, which help to anchor the animal to the base of its tube.

[5] After examination of genetic differences between annelids, Siboglinidae were placed within the order Polychaeta by scientific consensus.

[5] The oldest definitive specimens referred to the family came from Early Jurassic (Pliensbachian-Toarcian) Figueroa Sulfide deposits from San Rafael Mountains, found to be similar to modern Ridgeia.

[10] Separation of vestimentiferans into seep and deep-sea-dwelling clades is still debated due to some phylogenies based on sequencing data placing the genera along a continuum.

In a ventroanterior position in the vestimentum is the brain which is postulated to be simpler than relatives that maintain a gut in the adult form.

The sulfides are metabolized by symbiotic hydrogen sulfide- or methane-oxidizing bacteria living in an internal organ, the trophosome.

[16] This method of entry, known as horizontal transmission, means that each organism may have different species of bacteria assisting in this symbiosis.

Endosymbionts have a wide variety of metabolic genes, which may allow them to switch between autotrophic and heterotrophic methods of nutrient acquisition.