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Topic: Xiphosura

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	Research Publications
		A study of the palaeoecology of the Xiphosura along with a review of trace fossils produced by xiphosurans suggests that the evidence for freshwater lineages of xiphosurans is at best equivocal.
		Possible evolutionary trends in the xiphosuran fossil record identified here are: progressive loss of visible opisthosomal segments at tagma boundaries; fusion of the opisthosomal segments to form a thoracetron; differentiation of the opercular tergite belonging to somite VIII and a trend towards the prosoma and opisthosoma becoming equal to sub-equal in axial length.
		The synziphosurine (Chelicerata, Xiphosura) Cyamocephalus loganensis Currie, 1927 is known from two specimens from the UK: one from the Lesmahagow inlier, Scotland and another from Leintwardine, England.
	www.members.tripod.com /~Lyall/pubs.html (2520 words)

	Chelicerata - Wikipedia, the free encyclopedia
		The chelicerates and their closest fossil relatives (mostly originally included in the Xiphosura) form the group Arachnomorpha.
		In the Chelicerata, the body is divided into an anterior prosoma (or cephalothorax) composed of eight segments plus a presegmental acron and a posterior opisthoma (or abdomen) composed of twelve segments plus a postsegmental telson.
		The name Merostomata should be avoided because in all recent cladistic hypotheses it refers to a paraphyletic group composed by the Xiphosura + Eurypterida.
	en.wikipedia.org /?title=Chelicerata (392 words)

	Thoracetron - Wikipedia, the free encyclopedia
		Thoracetron is an entire plate formed by the fusion of opisthosomal tergites behind opercular tergite (free abdominal segments) in Xiphosura of the order Xiphosurida, being considered a synapomorphy for this order (Anderson and Selden, 1997).
		Fusion of opisthosomal tergites to form a thoracetron has previously been considered a characteristic of the xiphosuran superfamilies Euproopoidea Eller, 1938 and Limuloidea Zittel, 1885.
		Anderson, L. and Selden, P. Opisthosomal fusion and phylogeny of Palaeozoic Xiphosura.
	en.wikipedia.org /wiki/Thoracetron (173 words)

	RedOrbit - Science - A New Synziphosurine (Chelicerata: Xiphosura) From the Late Llandovery (Silurian) Waukesha ...
		The timing of the incorporation of the chilarial segment into the prosoma of xiphosurans is unknown in their fossil record and has implications for the numbering of opisthosomal segments, but in the absence of evidence to the contrary, the microtergite, or first visible opisthosomal segment, is here recognized as segment one.
		It has been suggested that a reduced first opisthosomal segment is a synapomorphy of the Xiphosura (which includes the paraphyletic synziphosurines) (Dunlop and Seiden, 1997).
		A new specimen of Weinbergeiner opitzi (Chelicerata: Xiphosura) from the Lower Devonian Hunsriick Slate, Germany.
	www.redorbit.com /news/display?id=132291 (4588 words)

	Lab 4 – Ecdysozoa - Arthropoda
		Xiphosura), the sea scorpions (Eurypterida), the Arachnida (spiders, scorpions, mites, and others), and the sea-spiders (Pycnogonida).
		The Xiphosura, Pycnogonida, and Eurypterida are all marine in distribution, however, the Arachnida are almost entirely terrestrial.
		Classification – The Chelicerata are divided into four main groups: horseshoe crabs (Xiphosura), the extinct sea scorpions (Eurypterida), sea –spiders (Pycnogonida), and the spiders, scorpions, mites, etc. (Arachnida).
	userwww.sfsu.edu /~efc/classes/biol170/lab/Laboratory4.htm (1259 words)

	Untitled Document (Site not responding. Last check: 2007-10-01)
		Xiphosura: horseshoe crab (a chelicerate arthropod) -- 450 m.y.
		Modernization index in Dipnoi: peak of evolutionary change at 300 m.y.
		Lack of evolution in Xiphosura due to a genetic constraint?
	www.eeb.uconn.edu /courses/245_01/Lec6_outline.htm (152 words)

	Lab 4 – Ecdysozoa - Arthropoda
		Chelicerata The Chelicerata are composed of the horseshoe crabs (Xiphosura), the sea scorpions (Eurypterida), the Arachnida (spiders, scorpions, mites, and others), and the sea-spiders (Pycnogonida).
		Classification The Chelicerata are divided into four main groups: horseshoe crabs (Xiphosura), the extinct sea scorpions (Eurypterida), sea-spiders (Pycnogonida), and the spiders, scorpions, mites, etc. (Arachnida).
		The Xiphosura differ from all other Chelicerata in having compound eyes.
	online.sfsu.edu /~jrblair/biol170/lab/Laboratory4.htm (1458 words)

	Embryonic development of the horseshoe crab Limulus polyphemus (Chelicerata, Xiphosura) with special reference to ... (Site not responding. Last check: 2007-10-01)
		Mittmann B. and Scholtz G. (2001) "Distal-less expression in embryos of Limulus polyphemus (Chelicerata, Xiphosura) and Lepisma saccharina (Insecta, Zygenomata) suggests a role in the development of mechanoreceptors, chemoreceptors, and the CNS" Dev Genes Evol 211 232-243
		Mittmann B. (2002) "Early neurogenesis in the horseshoe crab Limulus polyphemus and its implication for arthropod relationships" Biol Bull 203 (2), 221-222
		Mittmann, B. and Scholtz, G. (2003) "Development of the nervous system in the "head" of Limulus polyphemus (Chelicerata: Xiphosura): morphological evidence for a correspondence between the segments of the chelicerae and and of the (first) antennae of Mandibulata" Dev Genes Evol 213 (1), 9-17
	www.hu-berlin.de:54321 /forschung/fdb/english/PJ/PJ978.html (161 words)

	Xiphosura (Site not responding. Last check: 2007-10-01)
		Horseshoe crabs (Class Xiphosura) are an ancient group of primarily marine chelicerates.
		Despite their common name, they are actually more closely related to spiders, scorpions and other arachnids rather than true crabs (Crustacea) but it's easy to see how the two have been confused.
		Click on the links above for more information.
	www.people.ku.edu /~ramoore (162 words)

	Journal Of Arachnology Volume 29 Issue #3 Abstracts
		ABSTRACT Due to their widespread use as model systems and their reputation as living fossils, horseshoe crabs (Xiphosura) have been studied intensively by physiologists and paleontologists.
		Specifically, it is argued that Limulus retains a box-truss axial muscle system like that of plesiomorphic members of other arthropod groups, that this is also a plesiomorphic condition for Chelicerata, and that arachnids are united by the loss of one component of this system, the anterior oblique muscles.
		Combined with comparative morpho-logical and molecular evidence from previous studies, this study adds greater weight to the widely held view that, among extant chelicerates, Xiphosura and Arachnida are monophyletic sister groups and counters recent speculation that scorpions are more closely related to xiphosurans than to spiders, whipscorpions and other arachnids.
	www.americanarachnology.org /JoA_tocs/JOA_v29n3.html (1874 words)

	Arthropoda
		Euchelicerata Weygoldt 1986 = Xiphosura + Eurypterida + Arachnida
		The trilobites and "merostomes" (Xiphosura + Eurypterida) he included within the Arachnida.
		The group is herein considered to include the sub-taxa Trilobitoidea, Arachnomorpha, and Mandibulata, wherein lie the great diversity of familiar spiders, scorpions, crustaceans, myriapods and insects, as well as many of the famously problematic stem group arthropods known only from fossils: the marrellomorphs, Burgessia, and so on.
	www.peripatus.gen.nz /Taxa/Arthropoda (4878 words)

	xiphosuran - Wiktionary
		(zoology): Any member of the order Xiphosura, including horseshoe crabs.
		(zoology): Of or pertaining to the order Xiphosura.
		This page was last modified 19:04, 5 June 2006.
	en.wiktionary.org /wiki/xiphosuran (35 words)

	Carboniferous Horseshoe Crab
		Name: Arthropda, Chelicerata, Merostomata, Xiphosura, Bellinuridae, Bellinurus trilobitoides
		Description: Xiphosura (horseshoe crabs) are related to the extinct Eurypterids, and more distantly to spiders and scorpions.
		This one is most like the more common member of the Xiphosura Euproops danae found in the Mazon
	www.fossilmall.com /EDCOPE_Enterprises/invertebrates/invert26/invert-fossils-26.htm (236 words)

	SearchBuffer.com - Search for Xiphosura (Site not responding. Last check: 2007-10-01)
		Browse and compare a great selection of Xiphosura.
		Enter your city or zip code to find hundreds of listings in your area.
		Click here to get more listings for Xiphosura.
	www.searchbuffer.com /words/x/Xiphosura.html (58 words)

	[No title]
		Horseshoe Crabs (Merostomata) - Discusses eating habits, body covering, habitation, unique behavior, and medical uses of this species.
		Horseshoe Crabs Subclass Xiphosura - Contains introductory information on this species.
		From A Guide to Seashore Life in Singapore.
	botw.org /top/Science/Biology/Plants_and_Animals/Animalia/Arthropoda/Merostomata (497 words)

	A NEW SYNZIPHOSURINE (CHELICERATA: XIPHOSURA) FROM THE LATE LLANDOVERY (SILURIAN) WAUKESHA LAGERSTÄTTE, WISCONSIN, ... (Site not responding. Last check: 2007-10-01)
		A NEW SYNZIPHOSURINE (CHELICERATA: XIPHOSURA) FROM THE LATE LLANDOVERY (SILURIAN) WAUKESHA LAGERSTÄTTE, WISCONSIN, USA Journal of Paleontology - Find Articles
		FindArticles > Publications > Free > Reference and Education > Journal of Paleontology > Mar 2005 > Article
		Journal of Paleontology, Mar 2005 by Moore, Rachel A, Briggs, Derek E G, Braddy, Simon J, Anderson, Lyall I, Et al
	www.findarticles.com /p/articles/mi_qa3790/is_200503/ai_n11827023/pg_2 (567 words)

	Horseshoe Crab Clipart (Site not responding. Last check: 2007-10-01)
		Click here for help downloading and using TIFF files.
		Description: Horseshoe crabs represent an order called Xiphosura, from the fact that the end of the abdomen is furnished with a long sword-like spine.
		Keywords: Crustacean, invertebrates, crustacea, Arthropoda, king crab, horseshoe crab, Xiphosura
	etc.usf.edu /clipart/7300/7334/hrsshoe-crab_7334.htm (186 words)

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