Corynexochida

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Parent taxa:
(check the following menu and phylogeny - the taxon in bold refers to the topic on this page)


TRILOBITA
Taxonomy Phylogeny
o Arthropoda
`--o TRILOBITA
   |?-Agnostina
   `--+--o Redlichiida
      |  |--Olenellina
      |  `--Redlichiina
      |--Corynexochida
      |--Phacopida
      |--Lichida
      `--o Librostoma
         |--Proetida
         |--Harpetida [Harpoidea]
         |--Ptychopariida
         |?-Eodiscina
         `--Asaphida


Corynexochida


Illaenus schmidti var cardinalis, an Ordovician Corynexochid Trilobite of Family Illaenidae from the Wolchow River region near Saint Petersburg, Russia. Note the significant effacement, and robust blade-like genal spines.

Introduction

Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Middle Devonian. Like many of the other trilobite orders, Corynexochida contains many species with widespread characteristics.

The middle region of the cephalon (the glabella) is typically elongate, with the sides often spreading forward (pestle-shaped). Some species have glabellae that are effaced, meaning they are smooth and show little detail. The glabellar furrows (when not effaced) typically have a splayed arrangement. In most species, the hind pair on either side of the cephalon become spines that point sharply backwards, and the spinose tips of the anterior pairs of thoracic segments tend to become more and more forward directed toward the pygidium. The eyes are typically large. Pygidia are typically large, competing in size with the cephalon in some species.

The tips of the thoracic segments of many Corynexochida species are spine-like (though in some species they are flush with the sides and smooth. The thorax can have 2-12 segments (rarely more), but they more typically have 7-8.


(The following menu and phylogeny refers to subtopics of this page)


CORYNEXOCHIDA
Taxonomy Phylogeny

Ascii phylogenetic tree goes here


Reference/Link

Credits

DanielCD Wikipedia

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