Trilobite Order Corynexochida

Trilobites
 

Page within: Class Trilobita - Trilobite Classification
 

The members of trilobite Order Corynexochida (pronounced Cory-nex-o-chee-da) comprise a large and morophologically diverse and complex trilobite clade with a biostratigraphy range from the Lower Cambrian to the Middle Devonian. The Corynexochida are divided into three suborders, Corynexochina, Illaenina and Leiostegiina that have distinct differentiating characteristics. Strong evidence supports the well-accepted phylogeny that the corynexochids descended from the Redlichiina in the Lower Cambrian.
Trilobite Taxonomy
Trilobite Phylogeny
Phylum Arthropoda
Subphylum Chelicerata
or Subphylum Schizoramia *
Superclass Arachnomorpha *
Class Trilobita

    Order Agnostida
    Order Redlichiida
    Order Corynexochida
    Order Phacopida
    Order Lichida
    Order Proetida
    Order Harpetida
    Order Ptychopariida
    Order Asaphida
    Order Odontopleurida
    Order Nectaspida
Trilobite Relatives
o Arthropoda
`--o Trilobita
   |?-Agnostida
   |?-Eodiscina
   `--+--o Redlichiida
      |  |--Olenellina
      |  `--Redlichiina
      |--Corynexochida
      |--Phacopida
      |--Lichida
      |--Odontopleurida
      `--o Librostoma
         |--Proetida
         |--Harpetida
         |--Ptychopariida
         `--Asaphida
* Different taxonomies are found, most recently with trilobites contained in Superclass Arachnomorpha in Subphylum Schizoramia.

Order Corynexochida was greatly expanded by Fortey (1990) from the 1959 Treatise (Rasetti in Moore, 1959), where it contained only Cambrian families, to include Leiostegioidea and Scutelluina. To unite the expanded order, Fortey used the characteristically clavate glabellar shape, often concavesided, and frequently with splayed glabellar furrows, and conterminant hypostomal attachment. Because Ontogenies are well known for a number of genera (e.g., Chatterton, 1980), including late protaspides very like those of Illaenidae, the Illaenids were incorporated in the Corynexochida; hypostomes and rostral plate structures were also noted to be comparable between the two groups. Fortey also notes the primary differentiating characteristic between Cambrian and later corynexochids. Cambrian corynexochids are typified by the rostral plate that is fused to the hypostome, in contrast to Ordovician and younger representatives.

With the 1990 revisions, the morphological features uniting Corynexochida are: opisthoparian sutures; elongate pestle-shaped glabella, played furrows (unless effacement evident) with typically backward-pointing hind pair and anterior pairs pointing increasingly forward toward the cephalon; sometimes with pit-like furrows; ledge like cranidial borders, either conterminant or (in derived forms) impendent hypostome, and large eyes (sometimes arcuate). The Corynexochid thorax typically has 7 to 8 segments, often with spinose pleural tips, but species with from 2 to 12 segments are known. The pygidium is usually large, isopygous or subisopygous, of variable form, and sometimes spinose. (see trilobites glossay of terms)

 

Suborder Corynexochina

Subphylum Chelicerata
Class Trilobita
Order Corynexochida

    Suborder Corynexochina
          Superfamily Corynexochoidea
                Family Amgaspididae
                Family Corynexochidae 
                Family Dinesidae
                Family Dokimocephalidae 
                Family Dolichometopidae
                Family Dorypygidae
                Family Edelsteinaspidae
                Family Jakutidae
                Family Oryctocephalidae
                Family Zacanthoididae 
    Suborder Illaenina
                Family Styginidae
                Family Illaenidae
                Family Panderidae
                Family Tsinaniidae 
    Suborder Leiostegiina
          Superfamily Leiostegioidea
                Family Cheilocephalidae
                Family Illaenuridae
                Family Kaolishaniidae
                Family Leiostegiidae
                Family Pagodiidae
                Family Ordosiidae
                Family Shirakellidae 
Bathyuriscus
Olenoides nevadensis
Bathyuriscus fimbriatus
Suborder Corynexochina
Family Dolichometopidae
Middle Cambrian
Marjam Formation
Milliard County, Utah

Olenoides nevadensis
(Rare)
Suborder Corynexochina
Family Dorypygidae
Late, Lower Cambrian
Marjam Formation
Milliard County, Utah

Albertella longwelli
Glossopleura
Albertella longwelli
Suborder Corynexochina
Superfamily Corynexochoidea
Family Zacanthoididae
Middle Cambrian
Carrara Formation, Nevada
Glossopleura sp.
Suborder Corynexochina
Superfamily Corynexochoidea
Family Dolichometopidae
Middle Cambrian
Chisholm Shale, Millard County, Utah
Bathyuriscus Trilobite
Dorypyge Trilobite
Changaspis
Zacanthoides Trilobite
Bathyuriscus wasatchensis
Suborder Corynexochina
Family Dolichometopidae
Middle Cambrian
Spence Shale Formation
Box Elder County, Utah
Dorypyge swasii
Suborder Corynexochina
Family Dorypygidae
Middle Cambrian
Pierson Cove Formation
Millard County, Utah
Changaspis placenta
Suborder Corynexochina
Family Oryctocephalidae
Middle Cambrian
Hotang Formation
Guizhou, China
Zacanthoides grabaui
Suborder Corynexochina
Family Zacanthoididae
Middle Cambrian
Spence Sahle
Box Elder County, Utah
Albertella
     
Albertella cf longwelli
Suborder Corynexochina
Superfamily Corynexochoidea
Family Zacanthoididae
Middle Cambrian
Nye County, Nevada
     

Suborder Illaenina

Nanillaenus
Scabriscutellum
Kolihapeltis
Illaenus tauricornis
Nanillaenus americanus
Order Corynexochida, Family Illaneidae
Ordovician
Bowmanville, Ontario, Canada
Scabriscutellum furciferum
Suborder Illaenina
Family Thysanopeltidae
Devonian
Hamar Laghdad Formation
Ofaten, Morocco
Kolihapeltis chlupaci hollardi
Suborder Illaenina
Family Styginidae
Devonian
Laatchana, Morocco
Illaenus tauricornis
Ordovician
Suborder: Illaenina
Family: Illaenidae
Wolchow river, Russia
Platyscutellum
Illaenus dalmani
Illaenus schmidti
Vanuxemella contracta Trilobite
Platyscutellum sp.
Suborder Illaenina
Superfamily Illaenoidea
Family Styginidae
Devonian
Zerg, Morocco
Illaenus dalmani
Ordovician
Suborder: Illaenina
Family: Illaenidae
Wolchow river, Russia
Illaenus schmidti var cardinalis
Suborder Illaenina
Middle Ordovician
Wolchow river, Russia
Vanuxemella contracta
Suborder Corynexochina
Superfamily Corynexochoidea
Family Zacanthoididae
Middle Cambrian
Gordon Shale, Thompson Falls, Montana