Proetida is an order of

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 ...

that lived from the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

to the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

. It was the last surviving order of trilobite, dying out in the Permian-Triassic extinction event.

Description

These typically small trilobites resemble those of the order Ptychopariida, from which the new order Proetida was separated in 1975 by Fortey and Owens. Like the order Phacopida, the proetids have

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 ...

s that sometime have pits or small tubercles, especially on the

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

(middle portion of the head). Because of their resemblance to the Ptychopariida in some features, the proetids are included in the subclass Librostoma. Unlike the trilobites of the phacopid suborder Phacopina, whose

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

s are schizochroal, the proetids have the more common holochroal eyes. These eyes are characterized by close packing of biconvex

lenses A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

beneath a single

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

l layer that covers all of the lenses. Each lens is generally hexagonal in outline and in direct contact with the others. They range in number from one to more than 15,000 per eye. Eyes are usually large, and because the individual lenses are hard to make out, they look smooth and sometimes bead-like. The

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 ...

of proetids was made up of anywhere between 8–22 segments, but most commonly 10. Many also extend the backcorners of the headshield into so-called genal spines. These two features can aid in distinguishing proetids from some phacopid trilobites in the suborder Phacopina, to which they can be very similar.

Classification

Opinions about the composition of and the affinities within the proetids, and to other trilobites, have been very divergent over time. In 2011 it was suggested to retain in Proetida only the families

Proetidae Proetidae is a family (biology), family of Proetida, proetid trilobites. The first species appeared in the Upper Ordovician, and the last genera survived until the Middle Permian. However, if the closely related family Phillipsiidae is actually a ...

and Tropidocoryphidae. The remainder of the families should be combined in a new proposed order, Aulacopleurida (Adrian, 2011), that would consist of the families Aulacopleuridae, Brachymetopidae, Dimeropygidae, Rorringtoniidae, Scharyiidae, Bathyuridae, Telephinidae, Holotrachelidae and Hystricuridae (considered Proetida before), combined with the Ptychopariid families Alokistocaridae, Crepicephalidae, Ehmaniellidae, Marjumiidae, Solenopleuridae and Tricrepicephalidae. The reasoning for this proposed split is based on differences in early larval stages. While the remaining Proetida taxa have globular larvae very unlike the adult form, the Aulacopleurids have adultlike larvae with paired spines. Others observe that globular non-adult larvae also occur in some taxa within the proposed order Aulacopleurida. More recently

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis of both larval and adult characters suggests the proetids as earlier understood probably are

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

. Two larval characters are unique to all Proetida; the first is that the eye develops on the side of the headshield, not at the front, and the second is a forwardly tapering

that is distanced from the rim of the headshield. The analysis identifies the taxa Asaphida, Olenina and Phacopida (including the Holotrachelidae) as

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

s. The earliest branch in Proetida is the family Hystricuridae. This is followed by a branch that consists of the families Dimeropygidae and Toernquistiidae. At the third node, the superfamily Aulacopleuroidea (consisting of Aulacopleuridae and Brachymetopidae) split off. The fourth branch is the family Scharyiidae. The fifth branch consists of the families Roringtoniidae and Tropidocoryphidae. The sixth node combines a restricted Bathyuridae split off from ''Bathyurella'' with the family Proetidae (including Phillipsiidae, which, according to Lamsdell, has been demoted to the subfamily Phillipsiinae).

Taxonomy

The following superfamilies, families and genera are recognized:

Superfamily Aulacopleuroidea

Family Aulacopleuridae *'' Aulacopleura'' *'' Aulacopleuroides'' *'' Beggaspis'' *'' Chamaeleoaspis'' *'' Coignops'' *'' Cyphaspides'' *'' Cyphaspis'' *'' Dixiphopyge'' *'' Harpidella'' *'' Latecephalus'' *'' Malimanaspis'' *'' Maurotarion'' *'' Namuropyge'' *'' Otarion'' *'' Otarionides'' *'' Protocyphaspides'' *'' Pseudotrinodus'' *'' Songkania'' *'' Tilsleyia'' Family Brachymetopidae *'' Acutimetopus'' *'' Asiagena'' *'' Australosutra'' *'' Brachymetopella'' *'' Brachymetopus'' *'' Cheiropyge'' *'' Conimetopus'' *'' Cordania'' *'' Eometopus'' *'' Loeipyge'' *'' Mystrocephala'' *'' Proetidea'' *'' Radnoria'' *'' Spinimetopus'' Family Rorringtoniidae *'' Cyamella'' *'' Hanjiangaspis'' *'' Isbergia'' *'' Madygenia'' *'' Protarchaeogonus'' *'' Rorringtonia'' *'' Solariproetus''

Superfamily Bathyuroidea

Family Bathyuridae *'' Acidiphorus'' *'' Aksuaspis'' *'' Aponileus'' *'' Bathyurellus'' *'' Bathyurus'' *'' Benthamaspis'' *'' Bolbocephalus'' *'' Catochia'' *'' Ceratopeltis'' *'' Eleutherocentrus'' *'' Ermanella'' *'' Gignopeltis'' *'' Grinnelaspis'' *'' Hadrohybus'' *'' Jeffersonia'' *'' Licnocephala'' *'' Lutesvillia'' *'' Madaraspis'' *'' Peltabellia'' *'' Petigurus'' *'' Platyantyx'' *?'' Proscharyia'' *'' Psephosthenaspis'' *'' Pseudoolenoides'' *''Punka'' *'' Rananasus'' *'' Randaynia'' *'' Raymondites'' *'' Sinobathyurus'' *'' Strigigenalis'' *'' Uromystrum'' Family Dimeropygidae (including Celmidae) *'' Celmus'' *'' Dimeropyge'' *'' Dimeropygiella'' *'' Glaphurella'' *'' Ischyrotoma'' *'' Pseudohystricurus'' Family Holotrachelidae *'' Holotrachelus'' *'' Kinderlania'' Family Hystricuridae *'' Amblycranium'' *'' Etheridgaspis'' *'' Flectihystricurus'' *'' Genalaticurus'' *'' Glabretina'' *'' Guizhouhystricurus'' *'' Hillyardina'' *'' Hintzecurus'' *?'' Holubaspis'' *'' Hyperbolochilus'' *'' Hystricurus'' *'' Ibexicurus'' *'' Lavadamia'' *''

Nyaya Nyāya (Sanskrit: न्यायः, IAST: nyāyaḥ), literally meaning "justice", "rules", "method" or "judgment", is one of the six orthodox (Āstika) schools of Hindu philosophy. Nyāya's most significant contributions to Indian philosophy ...

'' *'' Omuliovia'' *'' Pachycranium'' *'' Paenebeltella'' *'' Parahystricurus'' *'' Paraplethopeltis'' *'' Politicurus'' *'' Psalikilopsis'' *'' Psalikilus'' *'' Rollia'' *'' Rossicurus'' *'' Tanybregma'' *?'' Taoyuania'' *'' Tasmanaspis'' *'' Tersella'' Family Raymondinidae? (including Glaphuridae) order placement considered uncertain by Adrain, 2011 *'' Glaphurina'' *'' Glaphurus'' *'' Raymondina'' *'' Tagazella'' *'' Varanella'' Family Telephinidae *'' Carolinites'' *'' Fialoides'' *'' Goniophrys'' *'' Oopsites'' *'' Opipeuterella'' *'' Paraphorocephala'' *'' Phorocephala'' *?'' Pyraustocranium'' *'' Telephina'' *'' Telephops'' Family Toernquistiidae *'' Chomatopyge'' *'' Mesotaphraspis'' *'' Toernquistia'' *?'' Toernquistina''

Superfamily Proetoidea

Family Phillipsiidae *'' Acanthophillipsia'' *'' Acropyge'' *'' Ameropiltonia'' *'' Ameura'' *'' Ampulliglabella'' *'' Anisopyge'' *'' Archegonus'' *'' Bedicella'' *'' Breviphillipsia'' *'' Carbonocoryphe'' *'' Cummingella'' *'' Delaria'' *'' Ditomopyge'' *'' Doublatia'' *'' Griffithidella'' *'' Griffithides'' *'' Grossoproetus'' *'' Hentigia'' *'' Hesslerides'' *'' Hildaphillipsia'' *'' Iranaspidion'' *'' Jimbokranion'' *'' Kollarcephalus'' *'' Microphillipsia'' *'' Neoproetus'' *'' Nipponaspis'' *'' Novoameura'' *'' Nunnaspis'' *'' Paraphillipsia'' *'' Persiax'' *'' Phillibole'' *'' Phillipsia'' *'' Piltonia'' *'' Pseudophillipsia'' *'' Simulopaladin'' *'' Spinibole'' *'' Thaiaspis'' *'' Thigriffides'' *'' Timoraspis'' *'' Triproetus'' *'' Vidria'' *'' Weania'' Family

*'' Aayemenaytcheia'' *'' Aceroproetus'' *'' Alaskalethe'' *'' Altajaspis'' *'' Anambon'' *'' Anglibole'' *'' Angustibole'' *'' Anujaspis'' *'' Appendicysta'' *'' Aprathia'' *'' Archaeocoryphe'' *'' Ascetopeltis'' *'' Astroproetus'' *'' Australokaskia'' *'' Bailielloides'' *'' Bapingaspis'' *'' Basidechenella'' *'' Beleckella'' *'' Belgibole'' *'' Benesovella'' *'' Bitumulina'' *'' Blodgettia'' *'' Bohemiproetus'' *'' Bolivicrania'' *'' Boliviproetus'' *'' Bollandia'' *'' Bonnaspidella'' *''Borealia'' *'' Brevibole'' *'' Burgesina'' *'' Calybole'' *'' Camsellia'' *'' Carbonoproetus'' *'' Carlopsia'' *'' Carniphillipsia'' *'' Ceratoproetus'' *'' Chauffouraspis'' *'' Chaunoproetoides'' *'' Chaunoproetus'' *'' Chiides'' *'' Chiops'' *'' Chlupacula'' *'' Chuanqianoproetus'' *'' Clavibole'' *'' Comptonaspis'' *'' Coniproetus'' *'' Conophillipsia'' *''Constantina'' *'' Coombewoodia'' *'' Craspedops'' *'' Crassibole'' *'' Crassiproetus'' *'' Cyphinioides'' *'' Cyphoproetus'' *'' Cyrtodechenella'' *'' Cyrtoproetus'' *'' Cyrtosymbole'' *'' Cystispina'' *'' Daihuaia'' *'' Dayinaspis'' *'' Dechenella'' *'' Dechenelloides'' *'' Dechenellurus'' *'' Deinoproetus'' *'' Deltadechenella'' *'' Diabole'' *'' Diacoryphe'' *'' Drevermannia'' *'' Dudu'' *'' Dushania'' *'' Effops'' *'' Ejinoproetus'' *'' Elegenodechenella'' *'' Elimaproetus'' *'' Elliptophillipsia'' *'' Endops'' *'' Engelomorrisia'' *'' Ensecoryphe'' *'' Eocyphinium'' *'' Eocyrtosymbole'' *'' Eodrevermannia'' *'' Eomicrophillipsia'' *'' Eopalpebralia'' *'' Eosoproetus'' *'' Eowinterbergia'' *'' Erbenaspis'' *'' Erbenites'' *'' Evagena'' *'' Exochops'' *'' Flexidechenella'' *'' Formonia'' *'' Francenaspis'' *'' Franconicabole'' *'' Frithjofia'' *'' Fuscinipyge'' *'' Ganinella'' *'' Gapeevella'' *'' Geigibole'' *'' Georhithronella'' *'' Gerastos'' *'' Gitarra'' *'' Globusia'' *'' Globusiella'' *'' Globusoidea'' *'' Gomiites'' *'' Gracemerea'' *'' Hassiabole'' *''Hedstroemia'' *'' Helioproetus'' *'' Helmutia'' *'' Helokybe'' *'' Humeia'' *'' Humilogriffithides'' *'' Hunanoproetus'' *'' Hypaproetus'' *'' Jinia'' *'' Karginella'' *'' Kaskia'' *'' Kathwaia'' *'' Kerpenella'' *'' Khalfinella'' *'' Kolymoproetus'' *'' Kosovoproetus'' *'' Krambedrysia'' *'' Kulmiella'' *'' Kulmogriffithides'' *'' Lacunoporaspis'' *'' Laevibole'' *'' Langgonbole'' *'' Latibole'' *'' Latiglobusia'' *'' Latiproetus'' *'' Lauchellum'' *'' Lichanocoryphe'' *'' Linguaphillipsia'' *'' Liobole'' *'' Liobolina'' *'' Longilobus'' *'' Longiproetus'' *'' Lophiokephalion'' *'' Lugalella'' *'' Luojiashania'' *'' Macrobole'' *'' Mahaiella'' *'' Malayaproetus'' *'' Malchi'' *'' Mannopyge'' *'' Megaproetus'' *'' Menorcaspis'' *'' Merebolina'' *'' Metaphillipsia'' *''Mezzaluna'' *'' Microspatulina'' *'' Mirabole'' *'' Monodechenella'' *'' Moravocoryphe'' *'' Moschoglossis'' *'' Myoproetus'' *'' Namuraspis'' *'' Neogriffithides'' *'' Neokaskia'' *'' Nitidocare'' *'' Nodiphillipsia'' *'' Oehlertaspis'' *'' Oidalaproetus'' *'' Orbitoproetus'' *'' Ormistonaspis'' *'' Omlistonia'' *'' Ormistoniella'' *'' Osmolskia'' *'' Otodechenella'' *''

Paladin The Paladins, also called the Twelve Peers (), are twelve legendary knights, the foremost members of Charlemagne's court in the 8th century. They first appear in the medieval (12th century) ''chanson de geste'' cycle of the Matter of France, wh ...

'' *'' Palaeophillipsia'' *'' Paleodechenella'' *'' Palpebralia'' *'' Panibole'' *'' Parachaunoproetus'' *'' Paradechenella'' *'' Parafrithjofia'' *'' Paraglobusia'' *'' Paragriffithides'' *'' Paramirabole'' *'' Parangustibole'' *'' Parapalpebralia'' *'' Paraproetus'' *'' Parawarburgella'' *'' Particeps'' *'' Parvidumus'' *'' Paryfenus'' *'' Pedinocoryphe'' *'' Pedinodechenella'' *'' Perexigupyge'' *'' Perliproetus'' *'' Phillibolina'' *'' Philliboloides'' *'' Phyllaspis'' *'' Planilobus'' *'' Planokaskia'' *'' Plesiowensus'' *'' Podoliproetus'' *'' Pontipalpebralia'' *'' Praedechenella'' *'' Pragoproetus'' *'' Prantlia'' *'' Prodiacoryphe'' *'' Proetocephalus'' *'' Proetus'' *'' Pseudobollandia'' *'' Pseudocyrtosymbole'' *'' Pseudodechenella'' *'' Pseudodudu'' *'' Pseudogerastos'' *'' Pseudoproetus'' *'' Pseudosilesiops'' *'' Pseudospatulina'' *'' Pseudowaribole'' *'' Pudoproetus'' *'' Pulcherproetus'' *'' Pusillabole'' *'' Raerinproetus'' *'' Reediella'' *'' Rhenocynproetus'' *'' Rhenogriffides'' *'' Richterella'' *'' Rijckholtia'' *'' Rosehillia'' *'' Rugulites'' *'' Schaderthalaspis'' *'' Schizophillipsia'' *'' Schizoproetina'' *'' Schizoproetoides'' *'' Schizoproetus'' *'' Semiproetus'' *'' Sevillia'' *'' Silesiops'' *'' Simaproetus'' *'' Sinobole'' *'' Sinocyrtoproetus'' *'' Sinopaladin'' *'' Sinoproetus'' *'' Sinosymbole'' *'' Skemmatocare'' *'' Skemmatopyge'' *'' Spatulata'' *'' Spergenaspis'' *'' Spinibolops'' *'' Struveproetus'' *'' Sulcubole'' *'' Tawstockia'' *'' Taynaella'' *'' Tcherkesovia'' *'' Tetinia'' *'' Thaiaspella'' *'' Thalabaria'' *'' Thebanaspis'' *'' Tropidocare'' *'' Tschernyschewiella'' *'' Typhloproetus'' *'' Unguliproetus'' *'' Vandergrachtia'' *'' Vittaella'' *'' Wagnerispina'' *'' Waideggula'' *'' Waigatchella'' *'' Warburgella'' *'' Waribole'' *'' Weberiphillipsia'' *'' Westropia'' *'' Weyeraspis'' *'' Winiskia'' *'' Winterbergia'' *'' Witryides'' *'' Xenadoche'' *'' Xenoboloides'' *'' Xenocybe'' *'' Xenodechenella'' *'' Xiangzhongella'' *'' Xiushuiproetus'' *'' Yanshanaspis'' *'' Yichangaspis'' *'' Yishanaspis'' *'' Yuanjia'' *'' Zhegangula'' *'' Zhejiangoproetus'' Family Tropidocoryphidae *'' Alberticoryphe'' *'' Astycoryphe'' *'' Bojocoryphe'' *'' Buchiproetus'' *'' Centriproetus'' *'' Cornuproetus'' *'' Cyrtosymboloides'' *'' Dalarnepeltis'' *'' Dalejeproetus'' *'' Decoroproetus'' *'' Denemarkia'' *'' Diademaproetus'' *'' Dipharangus'' *'' Eopiriproetus'' *'' Erbenicoryphe'' *'' Eremiproetus'' *'' Galbertianus'' *'' Gracilocoryphe'' *'' Gruetia'' *'' Guilinaspis'' *'' Ignoproetus'' *'' Interproetus'' *'' Koneprusites'' *'' Krohbole'' *'' Lardeuxia'' *'' Laticoryphe'' *'' Lepidoproetus'' *'' Linguaproetus'' *'' Lodenicia'' *'' Longicoryphe'' *'' Macroblepharum'' *'' Miriproetus'' *'' Nagaproetus'' *'' Paraeremiproetus'' *'' Paralardeuxia'' *'' Paralepidoproetus'' *'' Parvigena'' *'' Perakaspis'' *'' Phaetonellus'' *'' Phaseolops'' *'' Piriproetoides'' *'' Piriproetus'' *'' Pribylia'' *'' Prionopeltis'' *'' Prodrevermannia'' *'' Proetina'' *'' Proetopeltis'' *'' Pterocoryphe'' *'' Pteroparia'' *'' Quadratoproetus'' *'' Rabuloproetus'' *'' Ranunculoproetus'' *'' Remacutanger'' *'' Richteraspis'' *'' Rokycanocoryphe'' *'' Sculptoproetus'' *'' Slimanella'' *'' Spinoproetus'' *'' Stenoblepharum'' *'' Tafilaltaspis'' *'' Tropicoryphe'' *'' Tropidocoryphe'' *'' Vicinoproetus'' *'' Voigtaspis'' *'' Wolayella'' *'' Xiphogonium'' *'' Zetaproetus''

References

{{Taxonbar, from=Q1934211 Trilobite orders Early Ordovician first appearances Lopingian extinctions Taxa named by Richard Fortey Librostoma Fossil taxa described in 1975