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.
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
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
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
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
cf longwelli
Suborder Corynexochina
Superfamily Corynexochoidea
Family Zacanthoididae
Middle Cambrian
Nye County, Nevada
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Platyscutellum
sp.
Suborder Illaenina
Superfamily Illaenoidea
Family Styginidae
Devonian
Zerg, Morocco |
Illaenus
dalmani
Ordovician
Suborder: Illaenina
Family: Illaenidae
Wolchow river, Russia |
|
Vanuxemella
contracta
Suborder Corynexochina
Superfamily Corynexochoidea
Family Zacanthoididae
Middle Cambrian
Gordon Shale, Thompson Falls, Montana |
|
| |