Xiphosura
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Chelicerata Class: Xiphosura
Orders
Synziphosurida Xiphosurida Image File history File links Limulus_polyphemus. ... 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. ...

Xiphosura is a class of marine chelicerates which includes a large number of extinct lineages and only four recent species in the family Limulidae, which include the horseshoe crabs. The group has hardly changed in millions of years; the modern horseshoe crabs look identical to prehistoric genera such as the Jurassic Mesolimulus, and are considered to be living fossils. A class is the rank in the scientific classification of organisms in biology below Phylum and above Order. ... Classes Arachnida- spiders, scorpions, etc. ... Genera Carcinoscorpius Limulus Tachypleus Limulidae is the only family of the order Xiphosura and contains all the 4 living species known of the class Merostomata. ... 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. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Mesolimulus is an extinct genus of arthropod found in limestone in Bavaria, Germany. ... This article or section does not adequately cite its references or sources. ...

Xiphosura are typically placed the class Merostomata, comprising also the eurypterids, but this traditional usage in the past reflected the acceptation of an unnatural (paraphyletic) group. Although the name Merostomata can be seen in some textbooks, without reference to the Eurypterida, some individuals have urged that this usage should be discouraged (e.g. Boudreaux, 1979). Orders Order Eurypterida Order Xiphosura Merostomata is a class of marine Chelicerata which includes horseshoe crabs and eurypterids. ... Orders many, all extinct The eurypterids were the largest known arthropods that ever lived. ... In phylogenetics, a grouping of organisms is said to be paraphyletic (Greek para = near and phyle = race) if all the members of the group have a common ancestor, but the group does not include all the descendants of the most recent common ancestor of all group members. ...

Size

Minimum adult body size in Paleozoic species is 1-3 cm. Recent species may attain 60 cm. 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. ...

Characterization

Body covered with heavy mineralized cuticle, divided in anterior prosoma and posterior opisthosoma, this carrying a caudal spine (also referred to as a telson, though this same term is also used for a different structure in crustaceans). The cephalothorax is an anatomical term used of arachnid and malacostracan arthropods for the first major body section. ... The opisthosoma is the posterior portion of the arachnids body behind the prosoma. ... The telson is the last division of the body of a crustacean. ...

Prosoma dorsally covered by semicircular carapace which may bear eyes (median ocelli and lateral compound eyes) and ventrally the walking legs and chelicerae. Coxae of legs carry gnathobases performing mastication. Reduced appendages of absorbed first opisthosomal segment can still be seen as a sixth pair of small legs called chilaria. The term carapace refers to a dorsal section of an exoskeleton or shell, in a number of animal groups. ... 1 entry found for chelicerae. ...

Opisthosoma divided in into mesosoma, with flattened appendages and metasoma (posterior) without appendages. Mesosoma may have all segments fused forming a thoracetron.

Ecology

Recent Xiphosura are marine benthic living on soft substrate, coming ashore for reproduction. Based on the sediment associations, it was proposed that Paleozoic species were not marine, but lived in fresh water and brackish water. Seagrass growing off the coast of the Florida Keys. ...

Taxa removed from Xiphosura

There are two groups originally included in the Xiphosura, but which have been assigned to separate classes:

• Aglaspida Walcott 1911 (Cambrian to Ordovician).
• Chasmataspida Caster & Brooks, 1956 (Lower Ordovician).

Classification of the Xiphosura

Class Xiphosura Latreille, 1802

• †Order Synziphosurida
  • Weinberginidae Richter and Richter, 1929 (Lower Devonian)
  • Bunodidae Packard 1886
    • Bunodinae Packard 1886 (Upper Silurian to Downtonian)
    • Limuloidinae Størmer, 1952 (Upper Silurian)
  • Pseudoniscidae Packard 1886 (Upper Silurian)
  • Kasibelinuridae Pickett, 1993 (Middle Devonian to Late Devonian)
• Order Xiphosurida
  • †Suborder Bellinurina
    • Elleriidae Raymond, 1944 (Upper Devonian to Upper Carboniferous)
    • Euproopidae Eller, 1938 (= Liomesaspidae Raymond 1944) (Upper Carboniferous to Lower Permian)
    • Bellinuridae Zittel and Eastman, 1913 (Middle Devonian to Upper Carboniferous)
  • Suborder Limulina
    • †Rolfeiidae Selden and Siveter, 1987 (Early Carboniferous to Early Permian)
    • †Paleolimulidae Raymond, 1944 (Carboniferous to Permian)
    • †Moravuridae Pribyl, 1967 (Mississippian)
    • †Austrolimulidae + †Heterolimulidae (Middle Triassic)
    • Limulidae Zittel, 1885
      • †Mesolimulinae Størmer, 1952 (Lower Triassic to Cretaceous)
      • Limulinae Zittel, 1885
        • Tachypleini Pocock, 1902 (Miocene to Recent)
        • Limulini Zittel, 1885 (Recent)

For the Celtic language, see Southwestern Brythonic language; for the residents of the English county, see Devon. ... For other uses, see Silurian (disambiguation). ... President Bush- Deres gold in dem dere mines The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... “Mississippian” redirects here. ... The Triassic is a geologic period that extends from about 251 ± 0. ... // The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... The Miocene Epoch is a period of time that extends from about 23. ...

References

• Anderson, L. I. and P. A. Selden. 1997. Opisthosomal fusion and phylogeny of Palaeozoic Xiphosura. Lethaia 30:19-31.
• Boudreaux H. B., 1979. Arthropod phylogeny with special reference to insects. John Willey & sons, New York, Chichester, Brisbane, Toronto. 320 pp.
• Brusca, R. C. & Brusca, G. J. (2002) Invertebrates. Sinauer Associates, Massachusetts. 880 pages, 615 illustrations.
• Dunlop, J. A. 1997. Palaeozoic arachnids and their significance for arachnid phylogeny. Proceedings of the 16th European Colloquium of Arachnology, 65-82
• Dunlop, J.A.; Selden, P.A. 1997: The Early History and Phylogeny of the Chelicerates. In Fortey, R.A.; Thomas, R.H. (eds.) 1997: Arthropod Relationships. Systematics Association Special Volume Series 55, pp. 221-235.
• Rohdendorf B.B. (editor), Fundamentals of Paleontology, vol. 9, Arthropoda-Tracheata and Chelicerata: 894 pp. [1991 English translation of Russian original, Smithsonian Institution Libraries and National Science Foundation].
• Snodgrass, R.E., 1952. A textbook of arthropod anatomy. Hafner Publishing Company, New York.

External links

• Peripiatus - an overview of arthropod relationships.
• Paleos - a site with a synoptic account of the Xiphosura, focused on fossils.