Anopla (for changes in taxonomy, see reference from 2019) has long been used as name for a

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

of marine worms of the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

Nemertea Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of about 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. ...

, characterized by the absence of stylets on the

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

, the mouth being below or behind the brain, and by having separate openings for the mouth and proboscis. The other long used class of Nemertea are the

Enopla Enopla is one of the classes of the worm phylum Nemertea, characterized by the presence of a peculiar armature of spines or plates in the proboscis. Evolution and systematics The record of nemerteans is extremely sparse, as would be expected ...

(for changes in taxonomy, see reference from 2019). Although Anopla is a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

grouping, it is used in almost all

scientific classification image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

s. Anopla is divided into two

orders Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * H ...

Palaeonemertea Palaeonemertea is a class of primitive nemertean worm. It may be para- or polyphyletic, consisting of three to five clades and totalling about 100 species. These worms have several apparently simple features and, as their name suggests, they ar ...

and

Heteronemertea Heteronemertea is a Monophyly, monophyletic order (biology), order of about 500 species of nemertean worms. It contains genus, genera such as ''Lineus'' and ''Cerebratulus'', and includes the largest and most muscular nemerteans. Almost all hete ...

.Norenburg, J.; Gibson, R.; Herrera Bachiller, A.; Strand, M. (2019). World Nemertea Database. Anopla. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1293 on 2019-11-07 Palaeonemertea may be para- or

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

, consisting of 3-5 groupings and totalling about 100 species. These worms have several apparently simple features and, as their name suggests, they are often considered to be the most primitive nemerteans. The primary body-wall musculature consists of an outer circular stratum overlying a longitudinal stratum. The group includes genera such as '' Cephalothrix'' in which the nerve cords are inside the body-wall longitudinal muscle, and ''

Tubulanus ''Tubulanus'' is a genus of primitive nemertean worms in the order Palaeonemertea. Species The World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and co ...

'', in which the nerve cords are between the outer circular muscle and the epidermis. Tubulanids are commonly encountered in rocky areas of intertidal zones in the northern hemisphere. They are often bright orange or have very distinctive banding and or stripes and can be many meters long, although only a few mm thick. Heteronemertea is a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

grouping of about 500 species, containing genera such as ''

Lineus ''Lineus'' is a genus of nemertine worms, including the bootlace worm, arguably the longest animal alive. ''Lineus'' contains the following species: *'' Lineus acutifrons'' Southern, 1913 *'' Lineus albifrons'' Coe, 1934 *'' Lineus albocinctu ...

'' and ''

Cerebratulus ''Cerebratulus'' is a genus of nemerteans belonging to the family Lineidae. The genus has cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the ...

'' and including the largest and most

muscular MUSCULAR (DS-200B), located in the United Kingdom, is the name of a surveillance program jointly operated by Britain's Government Communications Headquarters (GCHQ) and the U.S. National Security Agency (NSA) that was revealed by documents release ...

nemerteans. Almost all heteronemerteans have three primary body-wall muscle strata, an outer longitudinal, middle circular, and inner longitudinal. The lateral nerve cords are outside the circular muscle, as in palaeonemerteans, but separated from the epidermis by the usually well-developed outer longitudinal muscle. A third subclass of Anopla called the Archinemertea was determined to be paraphyletic and is no longer used by most authors. A trace fossil genus called ''Archisymplectes'' from the

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the International Commission on Stratigraphy, ICS geologic timesc ...

found in central

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

was formerly placed in this subclass, but is now considered a Palaeonemertea, if indeed it is an Anopla.

References

* Moore, Janet (2001) ''An introduction to the invertebrates'' (Studies in Biology) Cambridge University Press, Cambridge, UK, ; * Thoney, Dennis A. and Schlager, Neil (eds.) (2004) "Anopla (''Anoplans'')" ''Grzimek's Animal Life Encyclopedia: Volume 1 - Lower Metazoans and Lesser Deuterostomes'' (2nd ed.) Thomson-Gale, Detroit, pp. 245–251 ; * Gibson, Ray (2002) ''The Invertebrate Fauna of New Zealand: Nemertea (Ribbon Worms)'' (NIWA Biodiversity Memoir No. 118) National Institute of Water and Atmospheric Research, Wellington, New Zealand, ; * Sundberg, Per; Turbeville, J. McClintock and Lindh, Susanne (2001) "Phylogenetic Relationships among Higher Nemertean (Nemertea) Taxa Inferred from 18S rDNA Sequences" ''Molecular Phylogenetics and Evolution'' 20(3): pp. 327–334; * Strand, Malin et al. (2019) "Nemertean taxonomy-Implementing changes in the higher ranks, dismissing Anopla and Enopla" ''Zoologica Scripta'' Vol. 48, nr 1, s. 118-119 DOI: 10.1111/zsc.12317 {{Authority control Nemerteans Paraphyletic groups