Pictorial Guide to the Trilobite Order Ptychopariida

PICTORIAL GUIDE
TO THE ORDER PTYCHOPARIIDA
last revised 30 June 2007 by S. M. Gon III

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Here are a few representative Ptychopariina:

Modocia	Densonella	Norwoodia	Tricrepicephalus	Conocoryphe	Modocia

Compare the pictorial format above with the descriptive narrative below:

ORDER PTYCHOPARIIDA
Introduction: An extremely large, heterogenous order, classification problematic, with specialized offshoots that are hard to frame within a general diagnosis.
Cephalon: typically with opisthoparian facial sutures, with gently forward-tapering simple glabella bearing a broad, rounded front (e.g., Olenina, Ptychopariina), but some with pronounced cephalic fringes (e.g., Harpina), usually with 3 pairs of rather narrow parallel glabellar furrows; natant hypostome.
Thorax: typically large with 8+ thoracic segments.
Pygidium: quite variable, but typically with a small pygidium bearing a border (Cambrian) or a larger pygidium with or without border (post-Cambrian).
Occurrence: Lower Cambrian to Upper Ordovician.
Suborders: Ptychopariina, Olenina.

Suborder Ptychopariina
Introduction: Primitive Ptychopariida, a large and extremely varied group.
Cephalon: glabella usually tapering with 3 pairs of glabellar furrows, sutures typically opisthoparian (but some proparian, and blind forms marginal); anterior sutures usually convergent to slightly divergent, posterior sections moderately to highly divergent; eyes usually present, medial, and near glabella; usually blade-like genal spines present.
Thorax: generally long, relative to pygidium.
Pygidium: variable, but typically smaller than thorax.
Superfamilies: Ellipsocephaloidea, Ptychparioidea (see below)
Families: (listing those for which suborder assignment is uncertain) Ityophoridae, Catillicephalidae, Raymondinidae, Avoninidae, Plethopeltidae.

PTYCHOPARIIDA includes two Suborders:

Ptychopariina

Olenina

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