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Merostomata
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Merostomata is a class of chelicerate arthropods that contains the extinct Eurypterida (sea scorpions) and the extant Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups.
Species
horseshoe crabs
CLASS
- KingdomAnimalia
- PhylumArthropoda
- ClassMerostomata
Xiphosura (/zɪfoʊˈsjʊərə/;[2] from Ancient Greek ξίφος (xíphos) 'sword', and οὐρά (ourá) 'tail', in reference to its sword-like tail) is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). They first appeared in the Hirnantian (Late Ordovician). Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera. The group has hardly changed in appearance in hundreds of millions of years; the modern horseshoe crabs look almost identical to prehistoric genera and are considered to be living fossils. The most notable difference between ancient and modern forms is that the abdominal segments in present species are fused into a single unit in adults. Xiphosura were historically placed in the class Merostomata, although this term was intended to encompass also the eurypterids, whence it denoted what is now known to be an unnatural (paraphyletic) group (although this is a grouping recovered in some recent cladistic analyses).[3] Although the name Merostomata is still seen in textbooks, without reference to the Eurypterida, some
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Wikidata facts
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- Haeckel Tachypleus Eurypterus.png
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- taxon name
- Merostomata
- Commons category
- Chelicerata
- taxon common name
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Article
4 sectionsContents
- Etymology
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Merostomata is a class of chelicerate arthropods that contains the extinct Eurypterida (sea scorpions) and the extant Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups.
==Etymology== The name "Merostomata" derives from the Greek roots (', "thigh") and (', "mouth"), in reference to the animals' possession of appendages which are mouthparts at their proximal end, but swimming legs at their distal end.