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Conodonts are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which are usually found in isolation and are now called conodont elements. Knowledge about soft tissues remains limited. They existed in the world's oceans for over 300 million years, from the Cambrian to the beginning of the Jurassic. Conodont elements are widely used as index fossils, fossils used to define and identify geological periods.
Agnatha is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct species. Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes.
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.
Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian series. It follows the Jiangshanian and precedes the Ordovician Tremadocian Stage. The proposed lower boundary is the first appearance of the trilobite Lotagnostus americanus around 489.5 million years ago, but other fossils are also being discussed. The upper boundary is defined as the appearance of the conodont Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 million years ago.
Westergaardodina is a species-rich genus of spine, U or W-shaped paraconodont known from Middle Cambrian to Lower Ordovician strata.
Iapetognathus is a genus of cordylodan conodonts. It is one of the oldest denticulate euconodont genera known.
Cordylodontidae is a family of conodonts.
Parapachycladina is an extinct genus of conodonts in the family Ellisoniidae, from the Early Triassic of the Beisi Formation in Guangxi Province, China.
Paraconodonts (Paraconodontida) are an extinct order of probable chordates, closely related or ancestral to euconodonts. The order contains the superfamily Furnishinacea, itself containing the families Westergaardodinidae and Furnishinidae.
Furnishinidae is an extinct family of paraconodonts.
Furnishina is an extinct genus of conodonts in the family Furnishinidae from the Cambrian.
Jerzy Dzik is a Polish paleontologist.
Proconodontus is an extinct genus of conodonts in the monotypic family Proconodontidae. The specimens are found in Cambrian formations.
Acanthodus is an extinct genus of conodonts.
Kallidontus is an extinct genus of conodonts.
Variabiloconus is an extinct genus of conodonts.
Eoconodontus is an extinct genus of conodonts of the Late Cambrian. It is a two-elements genus from the Proconodontus lineage.
Neospathodus is an extinct genus of conodonts.
Protoconodonts are an extinct group of Cambrian animals known from fossilized phosphatic tooth-like structures. They were originally described as an informal group of early conodonts, though more recent studies consider them to be more closely related to chaetognaths.
Protohertzina is a genus of conodonts or, possibly, Chaetognaths, found at the beginning of the Cambrian explosion.
References
- ↑ Late Cambrian conodonts of central Kazakhstan. GP Abaimova, Paleontologicheskii Zhurnal, 1978
- 1 2 Early Cambrian palaeobiogeography of the Zhenba–Fangxian Block (South China): Independent terrane or part of the Yangtze Platform?. Ben Yang, Michael Steiner and Helmut Keupp, Gondwana Research, 2015, volume 28 (4), pages 1543–1565, doi:10.1016/j.gr.2014.09.020
- ↑ Internal Structure of Cambrian Conodonts. K. J. Müller and I. Hinz-Schallreuter, Journal of Paleontology volume 72, No. 1 (Jan., 1998), pages 91-112 (Stable URL)
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