Ptychoparia is a genus of ptychopariid trilobites, and is the type genus of the family Ptychopariidae, and the order Ptychopariida. Fossils of the various species are found in Middle Cambrian-aged marine strata of Eurasia and North America, about 513 ± 0.3 to 499 ± 1.7 million years ago. Distribution Fossils have been found in Middle Cambrian marine strata of the Czech Republic, India, Mexico, Norway, South Korea, the United Kingdom, United States (Montana, New York, Virginia, and possibly Pennsylvania). Reassigned species Several species of trilobite that were originally assigned to Ptychoparia have now been moved to other genera. P. annio = Angusteva annio P. attleborensis = Hebediscus attleborensis P. batia = Chuangia batia P. breviceps = Oligometopus breviceps P. carolinensis = Etheridgaspis carolinensis P. enantiopa = Enantiaspis enantiopa P. fitchi = Hamptonella fitchi P. housensis = Bolaspidella housensis P. laeviceps = Asaphiscus laeviceps P. ligea = Probowmania ligea P. linnarssoni = Eldoradia linnarssoni P. llanoensis = Orygmaspis llanoensis P. matheri = Elvinia roemeri P. meglitzkii = Triangulaspis meglitzkii P. metra = Meteoraspis metra P. mutica = Mikaparia mutica P. occidentalis = Elrathia occidentalis P. oweni = Modocia nevadensis P. panope = Deadwoodia panope P. pernasutus = Dokimocephalus pernasutus P. pero = Wilbernia pero P. pia = Piaziella pia P. piochensis = Alokistocare piochensis P. prospectensis = Eldoradia prospectensis P. roemeri = Elvinia roemeri P. rogersi = Braintreella rogersi P. similis = Iddingsia similis P. spinifera = Annamitia spinifera P. suada = Dellea wilbernsensis P. subcoronatus = Alokistocare subcoronatum P. titiana = Inouyops titiana P. theano = Emmrichella theano P. toxeus = Solenoparia toxeus P. urania = Burnetiella urania P. unisulcata = Elvinia roemeri P. yunnanensis = Yunnanocephalus yunnanensis Description Like all Ptychopariidae, the dorsal exoskeleton in Ptychoparia has an inverse egg-shaped outline. The central raised axis, that is defined by a furrow, is moderately convex and narrow, at its widest about ⅛ of the maximum width of the headshield (or cephalon). The part of the axis in the cephalon, called glabella, tapers forward, is rounded-truncate at its front, is inserted by for pairs of furrows that do not contact across the midline, and one at the back that defines the occipital ring. The fourth pair of lateral furrows curve strongly inward until parallel with the midline. A border is defined by a furrow running parallel to the margin of the cephalon, and this border furrow is deep at the front.