Strophomenida is an extinct order of

articulate Articulate may refer to: * ''Articulate!'', a board game in which players describe words from different categories * Articulate brachiopods, brachiopods with toothed hinges and simple opening and closing muscles * Articulate sound, to move the ton ...

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

s which lived from the lower

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

period to the mid Carboniferous period. Strophomenida is part of the extinct class

Strophomenata Strophomenata is an extinct class of brachiopods in the subphylum Rhynchonelliformea. Orders Billingsellida An order that contains the suborder Clitambonitidina (and others?) . Orthotetida An order or superfamily that includes the Chilidiopsoi ...

, and was the largest known order of brachiopods, encompassing over 400

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

. Some of the largest and heaviest known brachiopod species belong to this class. Strophomenids were among the most diverse and abundant brachiopods during the

, but their diversity was strongly impacted at the

Late Ordovician mass extinction The Late Ordovician mass extinction (LOME), sometimes known as the end-Ordovician mass extinction or the Ordovician-Silurian extinction, is the first of the "big five" major mass extinction events in Earth's history, occurring roughly 443 Mya. It ...

. Survivors rediversified into new morphologies in the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoi ...

, only to be impacted once again at the

Late Devonian mass extinction The Late Devonian extinction consisted of several extinction events in the Late Devonian Epoch, which collectively represent one of the five largest mass extinction events in the history of life on Earth. The term primarily refers to a major ext ...

. However, they still survived till the mid Carboniferous. Adult strophomenids lack an opening for the pedicle (stalk), so in life, they either lay free or cemented the ventral valve (lower shell) onto a firm substrate at the umbo (hinge). In juveniles, a tiny hole for the pedicle was present on the ventral valve near the umbo, but this is closed up through development. The dorsal valve was typically concave or flat, though occasionally it was convex; the ventral valve was always convex. The hinge line at the rear of the shell was quite wide and strophic in shape, meaning that it was nearly straight. Many strophomenid shells are wider than long. The interior of the valves have a distinctive pseudopunctate microtexture: deflections in the mineralized shell layers stack up and unfurl into tiny bumps, which are usually supported by

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

rods known as a taleolae.

Subtaxa (superfamilies)

* †

Plectambonitoidea Plectambonitoidea is a suborder of brachiopods containing the Family (biology), families: *Family Plectambonitidae *Family Taffiidae *Family Bimuriidae *Family Syndielasmatidae *Family Leptellinidae *Family Grorudiidae *Family Leptestiidae *Fami ...

(

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

?) * †

Strophomenoidea Strophomenoidea is an extinct superfamily of prehistoric brachiopods in the order Strophomenida. Families - after * Amphistrophiidae * Christianiidae * Douvillinidae Douvillinidae is an extinct family of prehistoric brachiopods in the ...

Gallery

Image:StrophomenidCornulitidOrdovician.jpg, Strophomenid brachiopod with encrusting cornulitid tubeworm (Upper

, SE

Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th ...

). Image:Leptaena ventral dorsal Iowa.jpg, Strophomenid brachiopod ''Leptaena'' from the Upper Ordovician of

Iowa Iowa () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wiscon ...

References

Prehistoric animal orders Brachiopod orders Early Ordovician first appearances Carboniferous extinctions {{brachiopod-stub