''Ptychoparia'' is a genus of ptychopariid

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s, and is the

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

of the family

Ptychopariidae Ptychopariidae is a family (biology), family of trilobites, containing the following genera: *''Achlysopsis'' *''Altikolia'' *''Altitudella'' *''Amecephalites'' *''Asthenopsis'' *''Austinvillia'' *''Balangcunaspis'' *''Bashania (trilobite), Basha ...

, and the order

Ptychopariida 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–Siluria ...

. Fossils of the various species are found in Middle

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

-aged marine strata of Eurasia and North America, about 513 ± 0.3 to 499 ± 1.7 million years ago.

Description

Like all Ptychopariidae, the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

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 of the maximum width of the headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...

). The part of the axis in the cephalon, called glabella, tapers forward, is rounded-

truncate In mathematics and computer science, truncation is limiting the number of digits right of the decimal point. Truncation and floor function Truncation of positive real numbers can be done using the floor function. Given a number x \in \mathbb ...

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. The areas outside the axis are almost flat. Between the front of the glabella and the border, is a somewhat convex area of the cheek that is comparable in length (along the midline) to the occipital ring. In well preserved specimens the cheeks in front of the eye are adorned with very fine ridges (or striae) that probably represent parts of the

digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...

(see Kordule, 2006, p. 283, figure 2.a/f). The eye ridges are threadlike, evenly curved, extending from the anterior corners of the glabella to halfway the genal angles, while the visual surface makes an abrupt angle, is shaped like a bracket parallel to the midline and ± of the length of the cephalon. Like in most trilobites, the division between the outer free cheek (or librigena) and the inner fixed cheek (or fixigena) is a line (or suture) where the

splits to assist in

moulting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...

. It always follows the inside of the visual surface of the eye. In ''Ptychoparia'', the part of this suture behind the eye cuts to the posterior margin just to the inside of the genal spine (or the suture is gonatoparian), and the part in front of the eye diverges from the midline. There is a spine in the back corners of the cephalon (or genal spine) that reaches approximately to the third thorax segment, and is confluent with the outer margin of the cephalon. The articulate midsection of the body (or

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

) has 13 (''P. striata'') or 14 (''P. dubinka'') segments. Tail shield (or

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

) is slightly over half as wide as the cephalon (a state called micropygous). The pygidial axis (or rachis) has 5 or 6 rings and a termination and 4 or 5 ribs in the outlying pleural regions. The pygidium in ''Ptychoparia'' lacks a border.

Distribution

Fossils have been found in Middle Cambrian marine strata of the

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, the

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(

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, and possibly

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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''

References

{{Taxonbar, from=Q31246 Ptychopariidae Prehistoric life of Europe Ptychopariida genera Cambrian trilobites