Librostoma

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Librostoma is a [[trilobite]] [[subclass]] created in 1990 by [[Richard Fortey]] to encompass the trilobite orders [[Ptychopariida]], [[Harpetida]], [[Asaphida]], and [[Proetida]] that were previously included within order Ptychopariida.
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In the 1959 Treatise on Invertebrate Paleontology, what are now Orders Ptychopariida, Asaphida, Proetida, and Harpetida were grouped together as Order Ptychopariida, a huge and paraphyletic group. The subclass Librostoma was erected in 1990 by Fortey (1990) to encompass these orders that are united at least in earlier genera by a natant hypostomal condition. Subsequently, Ebach & McNamara (2002) raised Harpetida to an order status because its members lack a rostral plate and have a marginal facial suture.
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==References==
==References==
Fortey, R.A. 1990. Ontogeny, hypostome attachment and trilobite classification. Palaeontology 33:529-76.
Fortey, R.A. 1990. Ontogeny, hypostome attachment and trilobite classification. Palaeontology 33:529-76.

Revision as of 17:16, 4 March 2007

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