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Conodonts are extinct agnathan chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils found in isolation and now called conodont elements. Knowledge about soft tissues remains limited. The animals are also called Conodontophora to avoid ambiguity.
The Tremadocian is the lowest stage of Ordovician. Together with the later Floian stage it forms the Lower Ordovician epoch. The Tremadocian lasted from 485.4 to 477.7 million years ago. The base of the Tremadocian is defined as the first appearance of the conodont species Iapetognathus fluctivagus at the Global Boundary Stratotype Section and Point (GSSP) section on Newfoundland.
Promissum is an extinct genus of conodonts, primitive chordates, that lived during the Upper Ordovician period.
Prioniodontida, also known as the "complex conodonts", is a large clade of conodonts that includes two major evolutionary grades; the Prioniodinina and the Ozarkodinina. It includes many of the more famous conodonts, such as the giant ordovician Promissum (Prioniodinina) from the Soom Shale and the Carboniferous specimens from the Granton Shrimp bed (Ozarkodinina). They are euconodonts, in that their elements are composed of two layers; the crown and the basal body, and are assumed to be a clade.
Periodon is a genus of conodonts which existed in what is now Canada, Iran, Argentina, China, Russia, and the United States during the Ordovician Period. It was described by Hadding in 1913, and the type species is P. aculeatus.
The Richmond Group is a geologic group in Michigan. It preserves fossils dating back to the Ordovician period.
Iapetognathus is a genus of cordylodan conodonts. It is one of the oldest denticulate euconodont genera known.
Edward B. Branson was an American geologist and paleontologist. He worked at the University of Missouri.
Chirognathidae is an extinct family of conodonts.
Cornuodus is an extinct genus of conodonts.
Curtognathus is an extinct genus of conodonts from the Ordovician in the family Distacodontidae.
Erraticodon is an extinct genus of conodonts in the family Chirognathidae.
Paracordylodus is an extinct genus of conodonts in the clade Prioniodontida, also known as the "complex conodonts". The species P. gracilis has been recovered from the chert of the Narooma Terrane, a geological structural region on the south coast of New South Wales, Australia.
Amorphognathus is an extinct conodont genus in the family Balognathidae from the Ordovician.
Stig M. Bergström is a Swedish-American paleontologist.
Appalachignathus is a genus of multielement conodonts from the Middle Ordovician of North America.
Prioniodus is an extinct genus of conodonts in the family Balognathidae from the Ordovician.
Microzarkodina is an extinct genus of conodonts mainly from the Middle Ordovician of Baltoscandia. The Microzarkodina apparatus probably consisted of 15 or 17 elements: four P, two or four M and nine S elements. The S elements include different Sa, Sb1, Sb2, and Sc element types.
Histiodella is an extinct genus of conodonts.
Protoprioniodus is an extinct genus of conodonts.
References
- ↑ Ordovician Rhipidognathid Conodonts from Australia and Iran. Yong Y. Zhen, Robert S. Nicoll, Ian G. Percival, Mir Alireza Hamedi and Ian Stewart, Journal of Paleontology, Vol. 75, No. 1 (Jan., 2001), pages 186-207 (Stable URL)
