Strophomenida is an extinct order of
articulate 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, w ...
s which lived from the lower
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
period to the mid
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
period.
Strophomenida is part of the extinct class
Strophomenata, 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 nomenclat ...
. Some of the largest and heaviest known brachiopod species belong to this class. Strophomenids were among the most diverse and abundant brachiopods during the
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
, 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 Paleozo ...
, only to be impacted once again at the
Late Devonian mass extinction. However, they still survived till the mid Carboniferous.
[
Adult strophomenids lack an opening for the ]pedicle
Pedicle or pedicel may refer to:
Human anatomy
*Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures
...
(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 minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
rods known as a taleolae.
Subtaxa (superfamilies)
* † Plectambonitoidea (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
Gallery
Image:StrophomenidCornulitidOrdovician.jpg, Strophomenid brachiopod with encrusting cornulitid
Cornulitida is an extinct order of encrusting animals from class Tentaculita, which were common around the globe in the Ordovician to Devonian oceans, and survived until the Carboniferous.
The organisms had shells, and were subject to predation ...
tubeworm (Upper Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
, 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 s ...
).
Image:Leptaena ventral dorsal Iowa.jpg, Strophomenid brachiopod ''Leptaena'' from the Upper Ordovician of Iowa
Iowa () is a state in the 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: Wisconsin to the northeast, Illinois to the ...
.
References
Prehistoric animal orders
Brachiopod orders
Early Ordovician first appearances
Carboniferous extinctions
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