Pictorial Guide to the Trilobite Order Agnostida

PICTORIAL GUIDE
TO THE ORDER AGNOSTIDA

Suborder Agnostina : Superfamily Agnostoidea
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ORDER AGNOSTIDA
Suborder Agnostina
Superfamily Agnostoidea
Superfamily Condylopygoidea
Suborder Eodiscina

Suborder Agnostina

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Compare the pictorial approach above to the narrative equivalent below (salient features in color):

Suborder Agnostina
Cephalon: no facial sutures or eyes; cephalothoracic aperture present.
Thorax: 2 thoracic segments bearing distinctive articulating structures, but no articulating half-ring on anterior thoracic segment.
Pygidium: axis usually wide, inflated, 3 or fewer segments, one of which usually carries a tubercle; pygidial margin often bearing posterolateral spines. Cuticle thin.
Superfamilies: Agnostoidea and Condylopygoidea.

Superfamily Agnostoidea
Cephalon: with basal glabella lobes anteriorly directed, no clear occipital structure present, anterior glabellar lobe typically subequal in width to posteroglabella, or narrowing forward (not laterally expanded).
Thorax: as in typical Agnostina.
Pygidium: variable within bounds of typical Agnostina.

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AGNOSTIDA	REDLICHIIDA	CORYNEXOCHIDA
PHACOPIDA	ASAPHIDA	PROETIDA
LICHIDA	PTYCHOPARIIDA	HARPETIDA

last revised 12 DEC 2010 by S. M. Gon III