Errantia is a diverse group of marine

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class "

Polychaeta Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which ar ...

", it is currently regarded as a monophyletic group within the larger

Pleistoannelida Pleistoannelida is a group of annelid worms that comprises the vast majority of the diversity in phylum Annelida. Discovered through phylogenetic analyses, it is the largest clade of annelids, comprised by the last common ancestor of the highly di ...

, composed of Errantia and

Sedentaria Sedentaria is a diverse clade of annelid worms. It is traditionally treated as a subclass of the paraphyletic class Polychaeta, but it is also a monophyletic group uniting several polychaetes and the monophyletic class Clitellata. It is the sis ...

. These worms are found worldwide in marine environments and brackish water.

Phylogeny

The

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

s is slowly being resolved. Errantia and

are the two biggest clades of polychaetes, and together they compose clade

. Two groups are nested within Errantia:

Aciculata Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class "Polychaeta", it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Err ...

(

Eunicida Eunicida is an order of polychaete worms. Characteristics Members of this order have an elongated, segmented body and a distinct head, normally with a separate peristomium and prostomium. Many, but not all, live in tubes which vary from a muco ...

Phyllodocida Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine, though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in c ...

) and

Protodriliformia Protodriliformia is a clade of small marine polychaetes, comprised by the groups of meiofaunal interstitial worms Protodrilida and Polygordiidae, formerly considered " archiannelids". It is the most basal clade of Errantia. Evolutionary history P ...

( small meiofaunal worms such as the Protodrilida). Historically, the order Amphinomida was part of this subclass. However,

phylogenetic analyses In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

place Amphinomida inside a basal clade with

Sipunculida The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162 species of unsegmented marine annelid worms. The name ''Sipuncula'' is from the genus name '' Sipunculus'', and comes from the Latin ...

and '' Lobatocerebrum'', and this clade is the sister group to

. Some

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, such as

Spintheridae Spintheridae is a family of marine polychaete worms with a single genus, ''Spinther'', containing these species: * '' Spinther alaskensis'' Hartman, 1948 * '' Spinther arcticus'' (M. Sars, 1851) (includes Spinther miniaceus'' Grube, 1860) *'' S ...

and

Myzostomida The Myzostomida or Myzostomatida are an order of small marine worms, which are parasitic on echinoderms, mostly crinoids. These highly unusual and diverse annelids were first discovered by Friedrich Sigismund Leuckart in 1827. Morphology A ...

, are still difficult to place due to their long branching, but they likely belong to either Errantia or

Classification

Historical

Errantia is, along with

, one of the two old orders of the paraphyletic class "

". In 1977 the zoologist Kristian Fauchald split Errantia into three orders:

, Amphinomida and

, giving way to this classification. *Order Amphinomida – 2 families (

Amphinomidae Amphinomidae, also known as the bristle worms or sea mice, are a family of marine polychaetes, many species of which bear chaetae mineralized with carbonate. The best-known amphinomids are the fireworms, which can cause great pain if their toxin ...

Euphrosinidae The Euphrosinidae are a family of polychaete worms. The name is from Greek ''Euphrosyne'', meaning merriment; she was one of the three Graces In Greek mythology, the Charites ( ), singular ''Charis'', or Graces, were three or more goddesse ...

) *Order

**Superfamily Eunicea – 7 families (

Onuphidae The Onuphidae are a family of polychaete worms. Characteristics Most onuphids have tubes. Some live semisubmerged in the substrate, but others carry their tubes around, and they can all rebuild their tubes if necessary. The tubes, thin and parch ...

Eunicidae Eunicidae is a family of marine polychaetes (bristle worms). The family comprises marine annelids distributed in diverse benthic habitats across Oceania, Europe, South America, North America, Asia and Africa. The Eunicid anatomy typically co ...

Lumbrineridae Lumbrineridae is a family of polychaetes belonging to the order Eunicida Eunicida is an order of polychaete worms. Characteristics Members of this order have an elongated, segmented body and a distinct head, normally with a separate peristom ...

, Iphitimidae, Arabellidae, Lysaretidae,

Dorvilleidae Dorvilleidae is a family of polychaetes Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear man ...

) **Superfamily incertae sedis – 2 families (

Histriobdellidae Histriobdellidae is a family of annelids belonging to the order Eunicida. Genera: * ''Histriobdella'' Van Beneden, 1858 * ''Histriodrilus'' Foettinger, 1884 * ''Steineridrilus'' Zhang, 2014 * ''Stratiodrilus'' Haswell, 1900 References

{ ...

, Ichthytomidae) *Order

**Suborder Phyllodociformia – 4 families (

Phyllodocidae Phyllodocidae is a family of polychaete worms. Worms in this family live on the seabed and may burrow under the sediment. Characteristics Members of the Phyllodocidae are characterised by an eversible pharynx and leaf-like dorsal cirri. The hea ...

, Alciopidae, Lopadorhynchidae, Pontodoridae) **Suborder Aphroditiformia ***Superfamily Aphroditacea – 6 families ( Aphroditidae,

Polynoidae Polynoidae is a family of marine Polychaete worms known as "scale worms" due to the scale-like elytra on the dorsal surface. Almost 900 species are currently recognised belonging to 9 subfamilies and 167 genera. They are active hunters, but gene ...

, Polyodontidae, Pholoididae, Eulepethidae, Sigalionidae) ***Superfamily Chrysopetalacea – 2 families ( Chrysopetalidae, Palmyridae) ***Superfamily Pisionacea – 1 family ( Pisionidae) **Suborder Nereidiformia – 6 families ( Hesionidae, Pilargiidae, Syllidae, Calamyzidae, Nereidae, Antonbmunidae) **Suborder Glyceriformia – 3 families (

Glyceridae Glyceridae is a family of polychaete worms. They are commonly referred to as beak-thrower worms or bloodworms. They are bright red, segmented, aquatic worms. The proboscis worm '' Glycera'' is sometimes called bloodworm. The Glyceridae are epi- a ...

, Goniadidae,

Lacydoniidae Lacydoniidae is a family of polychaetes belonging to the order Phyllodocida. Genera: * '' Lacydonia'' Marion, 1874 References Polychaetes {{Annelid-stub ...

) **Suborder incertae sedis – 5 families (

Iospilidae Iospilidae is a family of polychaetes belonging to the order Phyllodocida. Genera: * ''Iospilopsis'' Augener, 1922 * ''Iospilus'' Viguier, 1886 * ''Paraiospilus'' Viguier, 1911 * ''Phalacrophorus'' Greeff, 1879 References

{{Taxonbar, from= ...

, Nephtyidae, Sphaerodoridae, Tomoptendae, Typhloscolecidae)

References

{{Taxonbar, from1=Q6759542, from2=Q2823177 Protostome subclasses