Merostomata
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Chelicerata Class: Merostomata
Orders
Order Eurypterida Order Xiphosura

Merostomata is a class of marine Chelicerata which includes horseshoe crabs and eurypterids. It includes only four living species but dozens of fossil species mainly from the Paleozoic. Some favor the abandonment of the term class Merostomata, in favour of splitting the class into two classes, Xiphosura and Eurypterida. This is because Merostomata is thought to be paraphyletic, with the Eurypterida more closely related to the Arachnida, forming the group Cryptopneustida (Boudreaux, 1979). This change has not been incorporated into most textbooks, which typically use the traditional "Merostomata" without reference to the Eurypterida. Pair of horseshoe crabs. ... For other uses, see Scientific classification (disambiguation). ... For other uses, see Animal (disambiguation). ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Classes Arachnida- spiders, scorpions, etc. ... In scientific classification used in biology, the order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). ... Orders many, all extinct The eurypterids were the largest known arthropods that ever lived. ... Orders see text Merostomata is a class of marine arthropods which includes horseshoe crabs and eurypterids. ... Classes Arachnida- spiders, scorpions, etc. ... Binomial name Linnaeus, 1758 The horseshoe crab, horsefoot, king crab, or sauce-pan (Limulus polyphemus, formerly known as Limulus cyclops, Xiphosura americana, Polyphemus occidentalis) is a chelicerate arthropod. ... Orders †Stylonuroidea Diener, 1924 †Eurypteroidea Burmeister, 1843 The eurypterids (sea scorpion) were the largest known arthropods that ever lived (with the possible exception of the Arthropleurids). ... For other uses, see Species (disambiguation). ... The Paleozoic Era (from the Greek palaio, old and zoion, animals, meaning ancient life) is the earliest of three geologic eras of the Phanerozoic eon. ... A class is the rank in the scientific classification of organisms in biology below Phylum and above Order. ... Orders see text Merostomata is a class of marine arthropods which includes horseshoe crabs and eurypterids. ... Orders many, all extinct The eurypterids were the largest known arthropods that ever lived. ... Paraphyletic - Wikipedia /**/ @import /skins-1. ... Orders Acarina Amblypygi Araneae Opiliones Palpigradi Pseudoscorpionida Ricinulei Schizomida Scorpiones Solifugae Uropygi The arachnids, Arachnida, are a class of invertebrate animals in the subphylum Chelicerata. ...

The Merostomata are the only chelicerates to possess compound eyes; the arachnids have lost the ancestral arthropods' fully developed latero-anterior compound eyes. Classes Arachnida- spiders, scorpions, etc. ... Compound eye of a dragonfly A compound eye is a visual organ found in arthropods such as insects and crustaceans. ... Orders Acarina Amblypygi Araneae Opiliones Palpigradi Pseudoscorpionida Ricinulei Schizomida Scorpiones Solifugae Uropygi The arachnids, Arachnida, are a class of invertebrate animals in the subphylum Chelicerata. ...

References

• Boudreaux H. B., 1979. Arthropod phylogeny with special reference to insects. John Willey & sons, New York, Chichester, Brisbane, Toronto. 320 pp.

External links

• http://www.earthlife.net/chelicerata/merostomata.html