Terebellida
Terebellida make up an order of the Polychaeta class, commonly referred to as "bristle worms". Together with the Sabellida, the Spionida and some enigmatic families of unclear taxonomic relationship, they make up the subclass Canalipalpata, one of the three main clades of polychaetes. Like most polychaetes, almost all members of the Terebellida are marine organisms. Most are small, sessile detritivores which live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorphies.
Systematics
There is little consensus on the number of families. Some treatments accept as little as five, while other authors list over a dozen. Here, the more inclusive view of the Terebellida is followed, based on a major review of polychaete systematics. Cladistic studies have hitherto only analyzed a rather small proportion of polychaetes; hence it may be that some of the families today included in Terebellida by most authors will eventually be again recognized to belong elsewhere.- Acrocirridae
- Alvinellidae
- Ampharetidae
- * Ampharetinae
- Cirratulidae
- Ctenodrilidae
- Fauveliopsidae
- Flabelligeridae
- Flotidae
- Pectinariidae
- Poeobiidae
- Sternaspidae
- Terebellidae
- Trichobranchidae
Notable species
A notable terebellid is the Pompeii worm, an alvinellid. It is the most heat-tolerant complex organism known on Earth. Found near hydrothermal vents deep in the Pacific Ocean, it thrives at a temperature of 50 °C. This is near the theoretical limit for eukaryotes, whose mitochondria disintegrate at about 55 °C.Seven species of pelagic terebellids have recently been discovered, including Swima in 2009 and Teuthidodrilus in 2010. These seven species have been assigned to four new genera, forming a phylogenetic clade within the Acrocirridae family.