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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 from a soft-bodied animal. The Cambrian fossil, ''Amiskwia'', has been interpreted as a nemertean based on its resemblance to some pelagic ribbon worms; however, this interpretation is disputed by many paleontologists. The enoplan nemerteans have been regarded as highly derived based on a more complicated muscle arrangement in the body wall and a more complex nervous system. However, whether this is a plesiomorphic or apomorphic character is not clear, and recent molecular studies are inconclusive in this respect.
Class Enopla used to be divided in two subclasses, Hoplonemertea and Bdellonemertea, but recent phylogenetic analyses based on nucleotide sequences show that Bdellonemertea should be included in Hoplonemertea. Hoplonemertea (in the old sense) contains two suborders, Monostilifera and Polystilifera. The encompasses those animals with a proboscis armature consisting of a single central stylet on a large cylindrical basis. The Polystilifera are armed with a pad, or shield, bearing numerous small stylets. The Polystilifera are further divided in two taxa, one (Pelagica) containing the pelagic species, and the other (Reptantia) with crawling or burrowing forms.
The class is currently divided into 30 families and 155 genera with approximately 650 described species. The two largest genera, ''Amphiporus'' and ''Tetrastemma'' contain 230 species, i.e., one third of all named species in the class. However, it must be made very clear that the systematics and classification of nemerteans are not based on a phylogenetic approach, and recent studies question the classification.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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