Introduction: distinctive group of typically very spinose trilobites with densely granulate or tuberculate exoskeletons; alternately placed as superfamily Odontopleuroidea in a broad concept of Order Lichida.
Cephalon: opisthoparian sutures; glabella extending to anterior border, lobation complex in advanced forms; simple holochroal eyes, usually not large; conterminant hypostome, not particularly large.
Thorax: variable, 8-13 segments, usually spine-tipped, sometimes greatly developed with distinctive spine patterns (e.g., Odontopleuroidea).
Pygidium: micropygous to subisopygous, with multiple pairs of spines, even in primitive forms (Dameselloidea).
Other: doublure not extensive, lacking terrace ridges
Occurrence: Middle Cambrian to Devonian (Frasnian) 
Superfamilies: Odontopleuroidea, Dameselloidea.

Introduction: typically very spinose and densely sculptured trilobites.
Cephalon: convex; glabella tapering forward or subparallel, extending to anterior margin or nearly so, less complex lobation than in sister order Lichida; eye ridges run from anterior end of glabella to palpebral lobe; opisthoparian sutures, often placed on sutural ridges; distinct notch in margin of free cheek adjacent to where anterior sutures intersect cephalic margin; facial sutures secondarily lost in some genera; genal spines typically present.
Thorax: 8 – 10 segments; tips of each bear 2 – 3 pairs of spines (anterior pair often difficult to see, ventrally directed); often with symmetrical rows of pleural spines or tubercles. 
Pygidium: micropygous, short, transverse, with 2 – 3 axial rings (3rd often faint), one or more pairs of tubular border spines, the largest of which connected to first axial ring by prominent ridge.
Occurrence: Upper Cambrian to Upper Devonian (Frasnian)
Families: Odontopleuridae
Genera: Odontopleuridae: Acanthalomina, Acidaspidella?, Acidaspides?, Acidaspis, Anacaenaspis (=Bruxaspis), Apianurus, Archaeopleura, Boedaspis, Borkopleura, Brutonaspis, Calipernurus, Ceratocara, Ceratocephala (=Bounyoungia; =Onchaspis; /Trapelocera), Ceratocephalinus, Ceratonurus, Chlustinia, Dalaspis, Diacanthaspis, Dicranurus, Dudleyaspis, Edgecombeaspis, Eoleonaspis (=Bojokoralaspis), Exallaspis, Gaotania, Globulaspis, Hispaniaspis, Isoprusia (=Mauraspis), Ivanopleura, Kettneraspis (=Grossia), Koneprusia, Laethoprusia, Leonaspis (=Acanthaloma), Meadowtownella, Miraspis (=Elbaspis), Ningnanaspis, Odontopleura, Orphanaspis, Periallaspis, Primaspis, Proceratocephala (=Drummuckaspis), Radiaspis (=Xanionurus; =Charybdaspis), Rinconaspis, Selenopeltis (=Languedopeltis; =Polyeres), Selenopeltoides, Sinespinaspis, Stelckaspis, Taemasaspis (=Gondwanaspis; =Snoderaspis), Uriarra, Whittingtonia.

Introduction: primitive Odontopleurida, surface finely to coarsely granulose.
Cephalon: opisthoparian sutures; glabella tapering forward, less complex lobation than in Odontopleuroidea; genal spines typically present.
Thorax: with up to 13 segments, less specialized than in Odontopleuroidea, more as in typical polymerids, but sometimes with extended spines.
Pygidium: longer pygidia than in Odontopleuroidea, with more axial segments; tapering axis, thicker-set marginal spines, 1-7 pairs of pleural pygidial spines of varying length
Occurrence: Middle Cambrian to Upper Cambrian(?)
Family: Damesellidae
Genera: Damesellidae: ?Adelogonus, Ariaspis, Bergeronites (=Spinopanura), Blackwelderia (=Parablackwelderia), Blackwelderioides, Chiawangella, Cyrtoprora, Damesella (=Hybowania; =Eodamesella), Damesops (=Meringaspis; =Paradamesops), Dipentaspis, Dipyrgotes, Drepanura, Duamsannella, Fengduia, Guancenshania, ?Hercantyx, Histiomona, Jiawangaspis, Liuheaspis, Metashantungia, Neodamesella, Palaeadotes, (=Pseudobergeronites), Paradamesella (=Falkopingia), Parashantungia, Pingquania (=Oxygonaspis), Pionaspis, Protaitzehoia, Pseudoblackwelderia, Shantungia, Stephanocare, Taihangshania, Taitzehoia, Teinistion (=Dorypygella), Xintaia, Yanshanopyge.

LITERATURE CITED:

Bruton, D. 1983. Cambrian origins of the odontopleurid trilobites. Palaeontology 26(4):875-85.

Campbell, M.J. & B.D.E. Chatterton. 2009. Silurian lichid trilobites from northwestern Canada: Ontogeny and phylogeny of lichids. J. Paleontol. 83(2):263-79.

Chatterton, B., R. Fortey, K. Brett, S. Gibb & R. McKellar. 2006. Trilobites from the upper Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara el Zguilma, southern Morocco. Paleontographica Canadiana 25:1-177., 54 pls.

Chatterton, B.D.E. & R. Ludvigsen. 2004. Early Silurian trilobites of Anticosti Island, Quebec, Canada. Palaeontologica Canadiana 22:1-264.