Orthida
Encyclopedia
Orthida is an extinct order of Brachiopods which appeared during the Early Cambrian period and became very diverse by the Ordovician
, living in shallow-shelf seas. Orthids are the oldest member of the subphylum Rhynchonelliformea , and is the order from which all other brachiopods of this group stem. Physically they are usually strophic, with well-developed interareas. They also commonly have radiating ribs, sulcus
, and fold structures. Typically one valve, often the brachial valve, is flatter than the other. The interior structure of the brachial valves are usually simple. In shape they are sub-circular to elliptical, with typically biconvex valves.
There is some debate over the forms that first appear of this order as to how they should be classified. However they begin to differentiate themselves by the late Early Cambrian period, and by the late Cambrian
period had diversified into numerous varieties and reach 2 to 5 cm in width. Specimens from the late Cambrian to the earliest Ordovician exhibit shells with rounded and pointed pedical valves, with sharp to obtuse extremities and ridges that are fine to course. Punctate shells appear during the mid-Ordovician, which establish the suborder Dalmanellidina. The Ordovician is a productive period which gives rise to numerous genera in this order, however they started to become greatly reduced by the end Ordovician extinction event. Both the impunctate and punctate survived through to the early Devonian
Eventually though, only the punctate lived on, and would play a minor role in benthic ecosystems until the late Permian
when they became extinct.
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
, living in shallow-shelf seas. Orthids are the oldest member of the subphylum Rhynchonelliformea , and is the order from which all other brachiopods of this group stem. Physically they are usually strophic, with well-developed interareas. They also commonly have radiating ribs, sulcus
Sulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
, and fold structures. Typically one valve, often the brachial valve, is flatter than the other. The interior structure of the brachial valves are usually simple. In shape they are sub-circular to elliptical, with typically biconvex valves.
There is some debate over the forms that first appear of this order as to how they should be classified. However they begin to differentiate themselves by the late Early Cambrian period, and by the late Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
period had diversified into numerous varieties and reach 2 to 5 cm in width. Specimens from the late Cambrian to the earliest Ordovician exhibit shells with rounded and pointed pedical valves, with sharp to obtuse extremities and ridges that are fine to course. Punctate shells appear during the mid-Ordovician, which establish the suborder Dalmanellidina. The Ordovician is a productive period which gives rise to numerous genera in this order, however they started to become greatly reduced by the end Ordovician extinction event. Both the impunctate and punctate survived through to the early Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Eventually though, only the punctate lived on, and would play a minor role in benthic ecosystems until the late Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
when they became extinct.