Aglaspidida

Aglaspidida; Temporal range: Cambrian –Ordovician PreꞒ Ꞓ O S D C P T J K Pg N
	Aglaspis spinifer
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
(unranked):	†Vicissicaudata
Order:	†Aglaspidida; Walcott, 1911
Families
	Aglaspididae; Lemoneitidae; Beckwithiidae; ?Strabopidae;

Aglaspidida, sometimes incorrectly termed "Aglaspida," is an extinct taxon of small, superficially horseshoe crab-like arthropods that were once regarded as basal or ancestral horseshoe crabs. However, anatomical comparisons demonstrate that the aglaspidids cannot be accommodated within the chelicerates.^[1] Now, though, they are regarded as a distinct group, possibly being close to the trilobites. An older hypothesis suggesting that they link trilobites with Chelicerata has fallen out of favour.
Aglaspid fossils are found throughout the world, including North America (upper Mississippi valley, Missouri and Utah), Europe, and Australia.

As of 1997, Hou & Bergström split off Strabopidae (which were once regarded as being primitive eurypterids), including the genera Strabops, Paleomerus, Parapaleomerus, and Neostrabops, as its own distinct order/taxon, "Strabopida."

List of Genera

References

^ Ortega-Hernández, J.; Braddy, S. J.; Jago, J. B.; Baillie, P. W. (2010). "A new aglaspidid arthropod from the Upper Cambrian of Tasmania". Palaeontology. 53 (5): 1065–1076. doi:10.1111/j.1475-4983.2010.00974.x.

Hesselbo, SP. 1992. Aglaspidida (Arthropoda) from the Upper Cambrian of Wisconsin. Journal of Paleontology 66(6)885-923.
Raasch, GO. 1939. Cambrian Merostomata. Geological Society of America Special Paper 19, 146p.

External links

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[Ortega2010-1] Ortega-Hernández, J.; Braddy, S. J.; Jago, J. B.; Baillie, P. W. (2010). "A new aglaspidid arthropod from the Upper Cambrian of Tasmania". Palaeontology. 53 (5): 1065–1076. doi:10.1111/j.1475-4983.2010.00974.x.

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