Here are two representative Anomocaroidea:
Compare the pictorial approach above to the narrative equivalent below (salient features in color):
Introduction: Primitive Asaphida (possibly ancestral to some other asaphine groups), including families retaining the natant hypostomal condition, as well as other ptychoparioid features; protaspides resembling those of Ptychopariida (not "asaphoid"); not all families included may be monophyletic (i.e., Anomocaroidea as described here is likely a paraphyletic group).
Cephalon: preglabellar field wide; glabella typically parallel or gently tapering, with 3 or 4 pairs of furrows more or less of ptychoparioid type, palpebral lobes long, sickle-shaped; natant hypostome, median ventral suture; natant hypostome, some approaching conterminant.
Thorax: 10-13+ segments.
Pygidium: typically large, with broad, usually concave border, 2-10 axial rings.
Families: Anomocaridae, Pterocephalidae, Housiidae, Parabolinoididae, Dikelokephalinidae.
Representative Genera: Anomocare, Anomocarina, Glyphaspis, Housia, Inouyella, Mapania, Labiostria, Pterocephalia.
Other notes: Aside from a large pygidium and the ventral median suture (which are diagnostic of Order Asaphida), Anomocaroids display several "primitive" Ptychoparioid characters such as: natant hypostome, ptychoparioid protaspis, and numerous thoracic segments. The families included in Anomocaroidea (Anomocaridae, Pterocephalidae, Housiidae, Parabolinoididae, and Dikelokephalinidae) are not united by any particular autapomorphy (shared derived character) and thus may be polyphyletic.
Walking Trilobite animation ©2000 by S. M. Gon III
All line drawings this page ©1999 - 2007 by S. M. Gon III