Conodont biostratigraphy

Conodonts are an extinct class of animals whose feeding apparatuses called ''teeth'' or ''elements'' are common microfossils found in strata dating from the Stage 10 of the Furongian, the fourth and final series of the Cambrian, to the Rhaetian stage of the Late Triassic. These elements can be used alternatively to or in correlation with other types of fossils (graptolites, trilobites, ammonites, ...) in the subfield of the stratigraphy named biostratigraphy.

Paleozoic conodonts

Cambrian conodonts

It is suggested that '' Eoconodontus notchpeakensis'' can be a marker of the Stage 10 of the Furongian, the fourth and final series of the Cambrian.

In 2006, a working group proposed the first appearance of '' Cordylodus andresi''. Currently the first appearance of ''E. notchpeakensis'' is favored by many authors because it is globally widespread and is independent of facies (known from continental rise to peritidal environments).

The ''Eoconodontus notchpeakensis'' proposal would also incorporate a non-biostratigraphic marker to correlate the beginning of Stage 10 globally. A carbon isotope excursion (the HERB-event) occurs in the lower part of the E. notchpeakensis range.

Ordovician conodonts

Early Ordovician

The base of the Tremadocian, the lowest stage of Ordovician, is defined as the first appearance of ''Iapetognathus fluctivagus'' at the GSSP section in Newfoundland.

No conodont species is associated with the Floian, the second stage of the Ordovician.

Middle Ordovician

The base of the Dapingian, the third stage of the Ordovician, is defined as the first appearance of ''Baltoniodus triangularis''.

The base of the Darriwilian, the fourth stage of the Ordovician, lies just above the North Atlantic '' Microzarkodina parva'' conodont zone. The base also lies in the upper part of the North American '' Histiodella altifrons'' conodont zone.

The Whiterock Stage refers mainly to the early Middle Ordovician in North America. It is often used in the older literature in a global sense. The Whiterock Stage is given a range from 471.8 (ca. 472) to 462 m.y.a., spanning close to 10 million years. Officially its start is defined by the potentially lowest occurrence of the conodont ''Protoprioniodus aranda'' or ''Baltoniodus triangularis''.

Late Ordovician

No conodont species is associated with the Sandbian, the Katian, nor with the Hirnantian, the fifth, sixth and seventh and final stages of the Ordovician.

''Baltoniodus gerdae'' has been found in the early Sandbian Bromide Formation, in Oklahoma, United States.

Silurian conodonts

Llandovery

The Llandovery epoch lasted from 443.8 ± 1.5 to 433.4 ± 2.8 mya, and is subdivided into three stages: the Rhuddanian, lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, and the Telychian.

The Telychian (Late Llandovery) of Estonia can be defined by five conodont zones (''Pterospathodus eopennatus ssp. n. 1'', ''P. eopennatus ssp. n. 2'', ''P. amorphognathoides angulatus'', ''P. a. lennarti'' and ''P. a. lithuanicus'').An updated Telychian (Late Llandovery, Silurian) conodont zonation based on Baltic faunas. Peep Männik, Lethaia, Volume 40, Issue 1, pp. 45–60, March 2007,

Wenlock

The Wenlock, which lasted from 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian (to 430.5 million years ago) and Homerian ages.

The Sheinwoodian (Wenlock) is defined between the acritarch biozone 5 and the last appearance of ''Pterospathodus amorphognathoides''. The global boundary stratotype point is in Hughley Brook in Apedale, U.K.

Ludlow

The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and the Ludfordian stage.

Přídolí

Devonian conodonts

Early Devonian

The Early Devonian lasts from 419.2 ± 2.8 to 393.3 ± 2.5 and begins with the Lochkovian stage, which lasts until the Pragian. This spans from 410.8 ± 2.8 to 407.6 ± 2.5, and is followed by the Emsian, which lasts until the Middle Devonian begins, 393.3± 2.7 million years ago.

Middle Devonian

The Middle Devonian comprises two subdivisions, the Eifelian giving way to the Givetian 387.7± 2.7 million years ago.

Late Devonian

Finally, the Late Devonian starts with the Frasnian, 382.7 ± 2.8 to 372.2 ± 2.5, followed by the Famennian subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian, 358.9± 2.5 million years ago. During that stage, a biologic event occurred (Upper Kellwasser Extinction of all '' Ancyrodella'' and '' Ozarkodina'' and most '' Palmatolepis'', '' Polygnathus'' and '' Ancyrognathus''). The Famennian (372.2 ± 1.6 mya) is defined by a GSSP Golden Spike located at Coumiac quarry, Montagne Noire, France where there is a biologic abundant occurrence of '' Palmatolepis triangularis''.

Carboniferous conodonts

Mississippian (also known as Lower Carboniferous)

The Tournaisian, the oldest age of the Mississippian contains eight conodont biozones:
* the zone of '' Gnathodus pseudosemiglaber'' and '' Scaliognathus anchoralis''
* the zone of ''Gnathodus semiglaber'' and '' Polygnathus communis''
* the zone of '' Dollymae bouckaerti''
* the zone of ''Gnathodus typicus'' and '' Siphonodella isosticha''
* the zone of ''Siphonodella quadruplicata'' and '' Patrognathus andersoni'' (upper zone of ''Patrognathus andersoni'')
* the lower zone of ''Patrognathus andersoni''
* the zone of ''Patrognathus variabilis''
* the zone of ''Patrognathus crassus''

The Visean, the second age of the Mississippian, contains four conodont biozones:
* the zone of '' Lochriea nodosa''
* the zone of ''Lochriea mononodosa''
* the zone of ''Gnathodus bilineatus''
* the zone of ''Gnathodus texanus''

The Serpukhovian, the third or youngest age of the Mississippian, includes four conodont biozones:
* the zone of ''Gnathodus postbilineatus''
* the zone of ''Gnathodus bollandensis''
* the zone of ''Lochriea cruciformis''
* the zone of ''Lochriea ziegleri''

Pennsylvanian (also known as Upper Carboniferous)

The Bashkirian, the oldest age of the Pennsylvanian, contains six biozones based on conodont index fossils:
* the zone of ''Neognathodus atokaensis''
* the zone of ''Declinognathodus marginodosus''
* the zone of ''Idiognathodus sinuosus''
* the zone of ''Neognathodus askynensis''
* the zone of ''Idiognathoides sinuatus''
* the zone of ''Declinognathodus noduliferus''

The base of the Moscovian