Errantia is a diverse group of

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

polychaete Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that ...

worms in the phylum Annelida. Traditionally a subclass of the

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

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 are m ...

", it is currently regarded as a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

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 div ...

, 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 sister ...

. 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 spec ...

s is slowly being resolved. Errantia and

are the two biggest

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s 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 cr ...

) 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 Small may refer to: Science and technology * SMALL, an ALGOL-like programming language * Small (anatomy), the lumbar region of the back * ''Small'' (journal), a nano-science publication * <small>, an HTML element that defines smaller text ...

meiofaunal worms such as the

Protodrilida Protodrilida is an order of polychaetes belonging to the 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 prot ...

). Historically, the order

Amphinomida Amphinomida is an order of marine polychaetes. The order contains two families: * ''Amphinomidae'' Lamarck, 1818 * ''Euphrosinidae The Euphrosinidae are a family of polychaete worms. The name is from Greek ''Euphrosyne'', meaning merriment; s ...

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

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 In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

. 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

class "

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

and

, giving way to this classification. *Order

– 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 Pontodoridae is a family of polychaetes belonging to the order 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 ...

) **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 Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their titular elongla ...

, Pholoididae, Eulepethidae,

Sigalionidae Sigalionidae is a family of polychaetes belonging to the order 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 benth ...

) ***Superfamily Chrysopetalacea – 2 families ( Chrysopetalidae, Palmyridae) ***Superfamily Pisionacea – 1 family (

Pisionidae Sigalionidae is a family of polychaetes belonging to the order 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 benth ...

) **Suborder Nereidiformia – 6 families (

Hesionidae Hesionidae are a family of phyllodocid "bristle worms" (class Polychaeta). They are (like almost all polychaetes) marine organisms. Most are found on the continental shelf; '' Hesiocaeca methanicola'' is found on methane ice, where it feeds ...

, Pilargiidae,

Syllidae Syllidae is a family of small to medium-sized polychaete worms. Syllids are distinguished from other polychaetes by the presence of a muscular region of the anterior digestive tract known as the ''proventricle''. Syllid worms range in size from ...

, Calamyzidae,

Nereidae Nereididae (formerly spelled Nereidae) are a family of polychaete worms. It contains about 500 – mostly marine – species grouped into 42 genera. They may be commonly called ragworms or clam worms. Characteristics The prostomium of ...

, 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 Goniadidae is a family of marine worms within the Polychaeta. Goniadids have long, slender bodies and can grow up to 260mm in length, although most are less than 50mm long. Goniadids have an eversible proboscis with a circlet of chitinous jaws ...

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