Ptychopariida

Life-forms

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: †Trilobitomorpha
Classis: †Trilobita
Ordo: †Ptychopariida
Subordines (2): †Olenina – †Ptychopariina

Overview of familiae

†Ityophoridae
...
Name

Ptychopariida Swinnerton, 1915
Vernacular names
中文: 褶頰蟲目

Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian extinction event.
Asaphiscus wheeleri, a Cambrian trilobite of the Superfamily Ptychoparioidea

Trilobites have facial sutures that run along the margin of the glabella and/or fixigena to the shoulder point where the cephalon meets the thorax. These sutures outline the cranidium, or the main, central part of the head that does not include the librigena (free cheeks). The eyes are medial along the glabella on the suture line (and some species have no eyes). The fossils of the moults of trilobites can often be told from the fossils of the actual animals by whether the librigena are present. (The librigena, or cheek spines, detach during moulting.) In ptychopariids, short bladelike genal spines are often present on the tips of the librigena.

The thorax is large and is typically made up of eight or more segments. The thorax is usually much longer than the pygidium, which is usually small. In some species the pygidium is outlined with a flat border.

The Subclass Librostoma was recently erected to encompass several related orders, including Ptychopariida, Asaphida, Proetida, Harpetida, and possibly Phacopida. These are now known as the "Librostome Orders". Trilobites of the orders Proetida, Harpetida, and of the family Damesellidae were originally placed in Ptychopariida.
Taxonomy

Suborder Olenina

Superfamily Olenoidea
Family Ellipsocephaloididae
Family Olenidae
Superfamily Incertae sedis
Genus Triarthrus

Suborder Ptychopariina

Superfamily Ellipsocephaloidea
Family Agraulidae
Family Aldonaiidae
Family Bigotinidae
Family Chengkouiidae
Family Ellipsocephalidae
Family Estaingiidae
Family Palaeolenidae
Family Yunnanocephalidae
Superfamily Ptychoparioidea
Family Acrocephalitidae
Family Alokistocaridae
Family Antagmidae
Family Asaphiscidae
Family Atopidae
Family Bolaspididae
Family Cedariidae
Family Changshaniidae
Family Conocoryphidae
Family Conokephalinidae
Family Crepicephalidae
Family Diceratocephalidae
Family Elviniidae
Family Eulomidae
Family Holocephalinidae
Family Ignotogregatidae
Family Inouyiidae
Family Isocolidae
Family Kingstoniidae
Family Liostracinidae
Family Llanoaspididae
Family Lonchocephalidae
Family Lorenzellidae
Family Mapaniidae
Family Marjumiidae
Family Menomoniidae
Family Nepeidae
Family Norwoodiidae
Family Papyriaspididae
Family Phylacteridae
Family Proasaphiscidae
Family Ptychopariidae
Family Shumardiidae
Family Solenopleuridae
Family Tricrepicephalidae
Family Utiidae
Family Wuaniidae
Superfamily Incertae sedis
Genus Tonopahella

Suborder incertae sedis

Family Avoninidae
Family Catillicephalidae
Family Ityophoridae
Family Plethopeltidae