TO THE ORDER AGNOSTIDA
Last revised 30 May 2005 by S.M.Gon III
ORDER AGNOSTIDA
Compare the pictorial approach to its narrative equivalent below (salient
features in color):
ORDER AGNOSTIDA
Compare the pictorial approach to its narrative equivalent below (salient
features in color):
| Introduction: Small trilobites
(usually only a few mm long) with cephalon and pygidium
strongly similar in outline and size (isopygous); enrollment typical.
Cephalon: cephalic shield with deeply parabolic outline, maximum width usually anterior of genal angle, sutures proparian or lacking; border convex; glabella fusiform, widest at base (except in Condylopygidae), glabellar segmentation highly variable, sometimes complex, but in some species entirely effaced; most species eyeless; hypostome natant, sometimes specialized with ribbon-like wings; rostral plate lacking (or uncalcified). Thorax: segments 2 (Agnostina) or 3 (some Eodiscina), axis typically broad, short fulcrate pleurae. Pygidium: strongly isopygous; pygidial margin typically closely matching cephalic margin. Occurrence: L. Cambrian to U. Ordovician (Ashgill). |
AGNOSTIDA includes two Suborders:
| Agnostina
|
and | Eodiscina
|
