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Topic: Ptychopariida

Related Topics

Proetida

Corynexochida

Lichida

Harpetida

Phacopida

Nektaspida

Asaphida

Redlichiida

Agnostida

Trilobite

Cambrian

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	PTYCHOPARIIDA FACT SHEET
		Defined largely by combinations of primitive character states (such as tapering glabella, preglabellar field, natant hypostome, small, furrowed pygidium, and subdued exoskeletal sculturing), the fate of the Ptychopariida may be to slowly dwindle as groups such as the Proetida, Asaphida, and Harpetida are defined via their shared derived characters and extracted from the Ptychoparid clade.
		The problem is exacerbated by the inadequate diagnoses of the constituent families; even the well-accepted clades within Ptychopariida, such as the Olenidae, are united by few shared derived characters, and, as in the Asaphida, there are primitive representatives lacking some of the derived states, and advanced representatives that have secondarily lost them.
		The process of clarifying the Ptychopariida is hampered by lack of complete specimens, lack of sufficient ontogenetic data, lack of hypostome characters, etc.
	www.trilobites.info /ordptychopariida.htm (1397 words)

	In order to distinguish trilobites from one another
		The recognition of Asaphida, Proetida, and Harpetida as orders is relatively recent, as in the 1959 Treatise they were all included within the very large order Ptychopariida.The Ptychopariida and Harpetida maintained the natant state until their extinction at the end of the
		They share several characters with the Ptychopariida (including a few species with natant hypostomes), so although the hypostomal condition of the Phacopida is typically conterminant (and impendent in some advanced Phacopina), which implies that they may have origininated with the natant Ptychopariida, making the Phacopida another late addition to the Libristomate subclass.
		However, many people point out their hypostomal condition, which ended at the same time, and similarities in the exoskeleton tuberculation of the Phacopida and Lichida orders.
	www.k12.nf.ca /gc/Science/Geology03/trilobites/Orders.htm (564 words)

	orderptychopariida
		The polyphyletic nature of the order Ptychopariida is well known.
		However, with larvae of about 40% of ptychopariid families described so far, we can reasonably think that larval characteristics will be of the utmost importance for solving this problem of polyphyly.
		Protaspid larvae of 17 (yellow and bold) of the 42 families have been described so far.
	www.geocities.com /barracudaaa/orderptychopariida.html (699 words)

	Agnostida - Wikipedia, the free encyclopedia
		The Agnostida are divided into two suborders -- Agnostina and Eodiscina -- that are then divided into a number of families.
		The Eodiscina appear to be "normal" trilobites with only two or three segments in the thorax; some resemble trilobites of the order Ptychopariida.
		As a group, agnostids have pygidia (tails) that are similar in size and shape to their cephalons (heads).
	en.wikipedia.org /wiki/Agnostida (301 words)

	Harpetida - Wikipedia, the free encyclopedia
		The Harpetida were formerly included in the family Ptychopariida, but were recently given their own order (Ebach and McNamara 2002).
		The subclass Librostoma was created in 1990 by Richard Fortey to cover the orders formally included with the Ptychopariida.
		The name Harpidae was once used as the name for the trilobite family containing the type genus Harpes.
	en.wikipedia.org /wiki/Harpetida (247 words)

	Trilobite systematics: The last 75 years Journal of Paleontology - Find Articles
		The coherence, or otherwise, of Proetida, Asaphida, Corynexochida and the lichid/odontopleurid groups will be resolved by such studies.
		The problems of paraphyly in Ptychopariida and Redlichiina may prove more obdurate.
		The temporal brevity of certain Cambrian family ranges may be partly a taxonomic artefact.
	www.findarticles.com /p/articles/mi_qa3790/is_200111/ai_n8958763/pg_29 (1024 words)

	Palaeos Invertebrates: Arthropoda: Trilobita: Order Ptychopariida (Site not responding. Last check: 2007-11-04)
		Please refer to the Trilobite Home Page by Sam Gon at Order Ptychopariida
		We thank Sam for permission to use his materials.
		However, Sam does a much better job maintaining his pages than we do.
	www.palaeos.com /Invertebrates/Arthropods/Trilobita/Ptychopariida.html (35 words)

	Trilobite Page
		Most of the clades that became extinct were already in long-term decline, whereas most of the clades that survived suffered no sustained diversity reduction after the extinction.
		Today there are nine generally recognised orders of trilobites: the Agnostida, Redlichiida, Corynexochida, Lichida, Phacopida, Ptychopariida, Harpetida, Asaphida and Proetida.
		1996) to be a suborder of the Ptychopariida, the diagnostic feature is a ventral median suture.
	www.peripatus.gen.nz /Taxa/Arthropoda/Trilobita/Trilobite.html (3066 words)

	TRILOBITEN - Fossilien erzaehlen die Geschichte des Lebens - Ptychopariida 2
		Eine große, heterogene Gruppe bilden die Ptychopariida, die bereits im Unteren Kambrium auftraten, aber auch schon mit Ausklang des Ordoviziums ihre Existenz beschlossen.
		Wenn man heutzutage in Sammlungen auf Trilobiten dieser Ordnung stößt, so handelt es sich zumeist um die unten zu bewundernden Elrathia, deren berühmt-berüchtigt guter Erhaltungszustand einen manchmal daran zweifeln lässt, daß diese Fossilien mehr als 500 Mio.
		In jedem Falle ist dieser kleine Trilobit besser zu betrachten als das niedliche Paar das wir auf der ersten Seite der Ordnung Ptychopariida ausgestellt haben, und das aus der Wheeler Formation stammt.
	www.trilobita.de /ptycho2.htm (559 words)

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