Introduction: typically spiny with densely granulate or tuberculate exoskeletons.
Cephalon: opisthoparian sutures; glabella broad, large, extending to anterior border, lobation simple (Odontopleuroidea) to complex, with fused lateral and glabellar lobes (Lichoidea); eyes typically present, holochroal, usually not large; conterminant hypostome.
Thorax: variable, 8-13 segments, usually spine-tipped, sometimes with distinctive spines (e.g., Odontopleuroidea).
Pygidium: typically isopygous to macropygous, but sometimes short (e.g., Odontopleuroidea), often longer than wide, often with 3 pairs of furrowed pleurae, typically ending in spinose tips.
Occurrence: Ordovician (Tremadoc) to Devonian (Frasnian) 
Superfamilies: Lichoidea, Odontopleuroidea, Dameselloidea