Asaphida Trilobites

The trilobites of order Asaphida are notably diverse in number of species and morphology, and interestingly contains about 20% of known species. The most differentating morphological feature of many Asaphid trilobites is the smooth and isopygous (similar in size) cephalon and pygidium, an evolutionary adaptation called effacement believed to have helped trilobites more easily burrow into and hide in sediment. Another theory is that the smoothing of the exoskeleton streamlined the trilobite for locamotion. Effacement is also evident among the Agnostids, and Suborder Illaenina of Order Corynexochida. The Asaphids appeared in the Middle Cambrian and persisted to the Lower Silurian. Order Asaphida comprises six Superfamilies: Anomocaroidea; Asaphoidea; Cyclopygoidea; Trinucleioidea; Dikelokephaloidea; and Remopleuridoidea as shown to the right. The major extinction event concluding the Ordovician Period markedly reduced trilobite diversity across all the orders. Among the Asaphids, only some members of superfamily Trinucleioidea survived, and they too met extinction near the end of the Silurian. Asaphids exhibit a large trilobite size range and contains the largest trilobite know, the apply named Isotelus rex, an important adaptive trait.

Subclass Librostoma*
Trilobite Order Asaphida

Suborder Asaphina
- Superfamily Anomocaroidea
- Superfamily Asaphoidea
- Superfamily Dikelokephaloidea
- Superfamily Remopleuridoidea
- Superfamily Cyclopygoidea
- Superfamily Trinucleioidea

* Subclass Librostoma contains Proetida, Harpetida, Ptychopariida, Asaphida

Also see: Asaphida Trilobites Classification

Asaphid Trilobite Fossils

Declivolithus alfredi Late Ordovician Suborder Asaphina Family Trinucleidae Tinjdad, Morocco	Isotelus mafritzi Middle Ordovician Suborder Asaphina Family Asaphidae Coburg Formation, Ontario, Canada	Isoteloides flexus Lower Ordovician Suborder Asaphina Family Asaphidae Fillmore Formation, Utah	Onnia superba Ordovician Suborder Asaphina Family Trinucleidae Blekos, Morocco

Orygmaspis Contracta Upper Cambrian Suborder Asaphina Family Parabolinoididae McKay Group, British Columbia	Trincleioidea indet Late Cambrian to Early Ordovician Suborder Asaphina Family Uncertain Jebel Saghrou, Morocco	Cryptolithus bellulus Late Ordovician Suborder Asaphina Family Trinucleidae Pulaski Shale, New York	Asaphellus sp Middle Ordovician Suborder Asaphina Family Asaphidae Zagora, Morocco

Dactylocephalus Trilobite Ordovician Suborder Asaphina, Superfamily Remopleuridioidea, Family Hungaiidae Fezouata, Morocco	Megistaspis triangularis Lower Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Lachnostoma latucelsum Middle Ordovician Suborder Asaphina Family Asaphidae Ninemile Shale, Nevada	Pseudogygites latimarginatus Upper Ordovician Suborder Asaphina Family Asaphidae Subfamily Isotelinae Collingwood Shale, Ontario, Canada

Asaphus raniceps Lower Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Niobella humfrayi Lower Ordovician Suborder Asaphina Family Asaphidae Table Head Formation Newfoundland, Canada	Paratrinucleus acervulosus Ordovician Suborder Asaphina Family Trinucleidae Table Head Formation Liberty Hall Shale, Virginia	Lloydolithus lloydi Silurian Suborder Asaphina Family Trinucleidae Middleton Formation, Shropshire, United Kingdom

Asaphus broggeri Lower Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Asaphus intermedius Middle Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Asaphus kowalewskii Middle Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Asaphus latus Middle Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia

Asaphus major Middle Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Asaphus punctatus Middle Ordovician Suborder Asaphina Family Asaphidae Saint Petersburg, Russia	Homotelus bromidensis Middle Ordovician Suborder Asaphina Family Asaphidae Criner Hills, Carter County, Oklahoma	Nankinolithis sp Ordovician Suborder Asaphina Family Trinucleidae El Kaid Errami, Morocco

Asaphida Trilobites

Subclass Librostoma* Trilobite Order Asaphida

Asaphid Trilobite Fossils

Subclass Librostoma*
Trilobite Order Asaphida