Odontopleurida is an order of very spinose trilobites closely related to the trilobites of the order Lichida. Some experts group the Odontopleurid families, Odontopleuridae and Damesellidae, within Lichida. Odontopleurids tend to have convex, bar-shaped cephalons, and lobed, knob-shaped glabella that extend to, or almost to the anterior margin. Many, if not almost all odontopleurids have long spines that are derived either from the margins of the exoskeleton, or from granular or tubercular ornamentation, or both. Many odontopleurids are so spinose so as to be described as having "spines on (their) spines." Odontopleurids have 8 to 13 thoracic segments, with Odontopleuridae odontopleurids having no more than 10, and Damesellidae odontopleurids having no more than 13. The pygidium tends to be very small, and invariably has long spines emanating from it in all known genera. Genera of Damesellidae are restricted to Middle to Upper Cambrian marine strata, and may represent a transition between Cambrian-aged lichids, and odontopleurids of Odontopleuridae. The odontopleurids of Odontopleuridae first appear in the Upper Cambrian, and go extinct before the end of the Frasnian stage of the late Devonian. Odontopleuridae Acanthalomina ?Acidaspidella ?Acidaspides Acidaspis Anacaenaspis Apianurus Archaeopleura Boedaspis Borkopleura Brutonaspis Calipernurus Ceratocara Ceratocephala Ceratocephalinus Ceratonurus Chlustinia Dalaspis Diacanthaspis Dicranurus Dudleyaspis Edgecombeaspis Eoleonaspis Exallaspis Gaotania Globulaspis Hispaniaspis Isoprusia Ivanopleura Kettneraspis Koneprusia Laethoprusia Leonaspis Meadowtownella Miraspis Ningnanaspis Odontopleura Orphanaspis Periallaspis Primaspis Proceratocephala Radiaspis Rinconaspis Selenopeltis Selenopeltoides Sinespinaspis Stelckaspis Taemasaspis Uriarra Whittingtonia Damesellidae ?Adelogonus Bergeronites Blackwelderia Blackwelderioides Chiawangella Cyrtoprora Damesella Damesops Dipentaspis Dipyrgotes Neodrepanura Duamsannella Fengduia Guancenshania ?Hercantyx Histiomona Jiawangaspis Karslanus Liuheaspis Metashantungia Neodamesella Palaeadotes, Paradamesella Parashantungia Pingquania Pionaspis Protaitzehoia Pseudoblackwelderia Shantungia Stephanocare Taihangshania Taitzehoia Teinistion Xintaia Yanshanopyge References Trilobite orders Miaolingian first appearances Frasnian extinctions