Introduction: large and variable group of related suborders; post-Cambrian, but presumably derived from Cambrian ancestors, perhaps natant Ptychopariida.
Cephalon: typically proparian (Phacopina and Cheirurina) or gonatoparian (Calymenina), preglabellar field often very short or absent, 4 or fewer pairs of glabellar furrows (these sometimes fused); eyes, when present, schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina); with rostral plates (Calymenina and Cheirurina) or without (some Phacopina); hypostome conterminant (all suborders) to impendent (some Phacopina).
Thorax: 8 – 19 segments, sometimes distinctly furrowed, axis sometimes broad (e.g., Homalonotidae).
Pygidium: typically micropygous (most Calymenina and Phacopina), but variable (e.g., subisopygous in Dalmanitoidea and Acastoidea), may be lobed or spiny (e.g., Cheirurina, some Dalmanitoidea, Acastoidea), or smooth-margined, with round or subtriangular outline (e.g., Calymenina, Phacopoidea).
Other: All suborders share similar ontogeny (bearing early protaspides with three pairs of prominent marginal spines, the hindmost pair post-cephalic, example at left) that in particular link the Calymenina to other Phacopida suborders.
Occurrence: Lower Ordovician (Tremadoc) to Upper Devonian (Famennian)
Suborders: Calymenina, Phacopina, Cheirurina.

last edited 08 July 2007 SMGIII

Cephalon: semicircular to subtriangular, typically with gonatoparian sutures (a few opisthoparian, e.g., Bathycheilidae, primitive Homalonotidae); glabella narrowing forwards; eyes holochroal, often small; hypostome conterminant, rostral plate present.
Thorax: 11 – 13 (typically 13), segments with rounded tips.
Pygidium: semicircular or triangular, without spinose margin.
Superfamilies/Families: Calymenoidea/Bathycheilidae, Bavarillidae, Calymenidae, Homalonotidae, Pharostomatidae.
Genera: 
Bathycheilidae: Bathycheilus (=Parabathycheilus), Calymenia, Eulomina.

last edited 09 NOV 2003 SMGIII

Cephalon: proparian sutures (sometimes fused), schizochroal eyes; glabella expands forwards; librigena typically yoked as single piece; hypostome conterminant to impendent, some with no rostral plate; some with genal spines.
Thorax: 10 to (typically) 11 segments, pleurae furrowed, articulating facets distinct, rounded, angular, or spinose tips.
Pygidium: typically smaller than cephalon (but subisopygous in Dalmanitoidea and Acastoidea), smooth or spinose.
Superfamilies: Phacopoidea, Dalmanitoidea, Acastoidea (See below)

Superfamily Dalmanitoidea
Cephalon: typically bearing genal spines, generally with well-developed preglabellar field, median region of glabella bearing muscle scars; eyes tend to mesial or posterior, true vincular furrows lacking.
Thorax: variable, but often with spinose tips.
Pygidium: typically subisopygous, often spinose (terminal or marginal spines); axial rings of consistent depth along length of pygidial axis, axial furrows with simple and consistent convergence angle.
Families: Dalmanitidae, Diaphanometopidae, Prosopiscidae
Genera: 
Dalmanitidae: Anchiopsis, Andreaspis, Argentopyge, Banilatites, Bessazoon, Blanodalmanites, Chacomurus, Chattiaspis, Coronura, Corycephalus, Crozonaspis, Dalmanites (/Dalmania; =Guaranites; =Hausmannia ETHERIDGE & MITCHELL; =Heliocephalus/Malvernia; =Makaspis; =Ommokris), Dalmanitina, Dalmanitoides, Dalmaniturus, Daytonia, Deloites, Delops, Destombesites, Dreyfussina (=Prephacopidella), Duftonia, Eodalmanitina, Eudolatites, Fenestraspis, Forillonaria, Francovichia, Furacopyge, Gamonedaspis, Glyptambon, Guichenia, Huntoniatonia (/Huntonia), Kasachstania, Lygdozoon, Malladaia, Morgatia, Mucronaspis (=Guaykinites), Mytocephala (=Mirops), Neoprobolium, Odontocephalus, Odontochile (/Hausmannia HALL & CLARK), Ormathops, Pericopyge, Phalangocephalus, Preodontochile, Prodontochile, Prosocephalus, Retamaspis, Reussiana, Roncellia, Schoharia, Songxites, Struveria, Synphoria (/Eocorycephalus; /Neosynphoria), Synphor oides, Thuringaspis, Toletanaspis, Trypaulites, Vokovicia, Zeliszkella, Zlichovaspis (=Devonodontochile; =Spinodontochile).

Superfamily Acastoidea
Cephalon: axial furrows slightly to moderately divergent, anterior glabellar lobes and furrows usually not fused (although furrows may be indistinct), eyes typically distant from posterior border furrows, but not strongly anterior; frontal glabellar lobe auxilliary impression system triangular in outline, maximum width of glabella adjacent to preglabellar furrow, median region of glabella devoid of muscle scars; cephalic margin "shouldered," laterally convex course of genal margin topographically distinct from curvature of axial margin
Thorax: pleural endings blunt, rounded, or angular, sometimes spinose.
Pygidium: micropygous to subisopygous, sometimes spinose (expressed as marginal spines), pygidial axis with deep, apodemal anterior ring furrows, with abrupt transition to shallow posterior ring furrows; coincident decrease in angle of axial furrow convergence.
Other: often similar in general body form to Phacopoidea via convergent evolution, but glabellar and other differences as noted above.
Families: Acastidae, Calmoniidae.
Genera: 
Acastidae: Acastava, Acaste, Acastella, Acastellina, Acastocephala, Acastoides, Acastopyge, Armorigreenops, Asteropyge, Baniaspis, Bellacartwrightia, Bradocryphaeus, Braunops, Breizhops, Centauropyge, Chimaerastella, Coltraneia, Comura, Cryphina, Delocare, Deloops, Destombesina, Dunopyge, Echinopyge, Erbenochile, Ewacaste, Feruminops, Gourdonia, Greenops, Gudralisium, Hallandclarkeops, Harringtonacaste, Heliopyge (=Alcaldops), Hexacosta, Hollardops (=Modellops; =Philipsmithiana), Kayserops, Kennacryphaeus, Kloucekia, Llandovacaste, Metacanthina, Mimocryphaeus, Morocconites, Mrakibina, Neocalmonia, Neometacanthus, Paracryphaeus, Pelitlina, Phacopidina, Philonyx, Pilletina, Protacanthina, Pseudocryphaeus, Psychopyge, Quadratispina, Quadrops, Radiopyge, Rheicops, Rhenops, Saharops, Sanidopyge, Scotiella, Sokhretia, Stummiana, Talus, Tolkienia, Treveropyge, Turcopyge, Walliserops.

last edited: 09 NOV 2003 SMGIII

Cephalon: proparian sutures (a few opisthoparian), glabella usually expanding forwards or barrel-shaped, up to 4 pairs of furrows; holochroal eyes, often small; gena often with fine pitting; with rostral plate; hypostome conterminant, with anterior wing bearing prominent process.
Thorax: variable numbers of distinctive segments within Phacopid range of 8-19, often spine-tipped.
Pygidium: often highly modified with 2-16 distinct pairs of ribs, and lobed or spinose margin.
Other: often with tuberculate exoskeleton.
Superfamilies/Families: Cheiruroidea/Cheiruridae, Encrinuridae (including Staurocephalidae), Pilekiidae, Pliomeridae.
Genera: 
Cheiruridae: Acanthoparypha, Actinopeltis HAWLE & CORDA, Anasobella, Ancyginaspis, Apollonaspis, Arcticeraurinella, Areia, Areiaspis, Azyptyx, Barrandeopeltis, Borealaspis (=Alreboaspis), Bornholmaspis, Bufoceraurus, Ceraurinella (=Bartoninus), Ceraurinium, Ceraurinus (=Remipyga), Cerauromeros, Cerauropeltis, Ceraurus (=Eoceraurus), Cheirurus, Chiozoon, Contracheirurus, Courtessolium, Crotalocephalides, Crotalocephalina (/Gibbocephalus; =Mezocrotalus), Crotalocephalus (=Cerauroides; =Pilletopeltis/Boeckia PILLET), Cyrtometopella, Cyrtometopus, Deiphon, Didrepanon, Eccoptochile, Eccoptochiloides, Forteyops, Foulonia, Gabriceraurus, Geracephalina, Hadromeros, Hammannopyge, Hapsiceraurus, Heliomera, Heliomeroides, Holia (=Ainoa), Hyrokybe (=Shiqiania), Junggarella, Kawina (=Cydonocephalus), Kolymella, Krattaspis, Ktenoura, Laneites, Lehua, Leviceraurus, Nieszkowskia, Onycopyge, Osekaspis, Pandaspinapyga, Paraceraurus, Parasphaerexochus (=Mayopyge), Parayoungia (=Ichiyamella), Parisoceraurus, Pateraspis, Patomaspis, Placoparina, Pompeckia, Proromma, Protocerauroides, Pseudocheirurus, Pseudosphaerexochus (=Zethus), Radiurus, Ratinkaspis, Reraspis, Skelipyx, Sphaerexochus (=Korolevium; =Onukia; =Parvixochus), Sphaerocoryphe (=Ellipsocoryphe; =Hemisphaerocoryphe), Stubblefieldia, Sycophantia, Turantyx, Valongia, Whittakerites, Xylabion, Xystocrania (=Xialiangshania), Youngia, Zazvorkaspis.

last revised 23 FEB 2004