Conodont

Conodonts are an extinct class of the phylum Chordata. They are now regarded as vertebrates, though the issue is still a live one.

For many years conodonts were known only from their feeding apparatus, which fossilises well. This is because most of the conodont animal was soft-bodied, so everything but the teeth were not fossilised in normal circumstances.

It was not until early 1980s that the conodont teeth were found with trace fossils of the host organism. It came from the Lower Carboniferous lagerstätte near Edinburgh, Scotland.

 Conodont elements 
The 'teeth', called conodont elements, are very common in the fossil record, and have been used in biostratigraphy.

They are also used as palaeothermometers. This is because under higher temperatures the phosphate undergoes colour changes, which are measured with the conodont alteration index. This has made them useful for petroleum exploration in rocks dating from the Cambrian to the Upper Triassic.

 Description of the animal 
Eleven fossil imprints of conodont animals are known. They depict an eel-like creature with 15 or, more rarely, 19 elements forming a bilaterally symmetrical array in the head. This array was a feeding apparatus different from the jaws of modern animals.  

There are three forms of teeth, coniform cones, ramiform bars, and pectiniform platforms, which may have performed different roles.

The organisms range from a centimeter or so to the giant Promissum, 40 cm in length. It is now widely agreed that conodonts had large eyes, fins with fin rays, chevron-shaped muscles and a notochord.

The entire class of Conodonts, or at least what was left of them at the time, were wiped out by the Triassic–Jurassic extinction event, which occurred roughly 200 million years ago.The extinction of conodonts – in terms of discrete elements – at the Triassic-Jurassic boundary

 Families and genera 
Conodonta Pander, 1856 non Eichenberg, 1930 sensu Sweet & Donoghue, 2001 [Conodontia; Conodontophorida Eichenberg, 1930; Conodontochordata]

 Paraconodonta Müller, 1962 [Paraconodontida]
 Amphigeisiniformes
 Amphigeisinidae Miller, 1981
 Westergaardodiniformes Lindström, 1970
 Westergaardodinidae Müller, 1959 [Chosonodinidae]
 Furnishinidae Müller & Nogami, 1971
 Conodontophora Eichenberg, 1930
 Cavidonti Sweet, 1988
 Proconodontiformes Sweet, 1988
 Pseudooneotodidae Wang & Aldridge, 2010
 Proconodontidae Lindström, 1981
 Cordylodontidae Lindström, 1970 [Cyrtoniodontinae Hass, 1959]
 Fryxellodontina
 Fryxellodontidae Miller, 1981
 Pygodontidae Bergstrom, 1981
 Belodellina Sweet, 1988
 Ansellidae Faohraeus & Hunter, 1985
 Dapsilodontidae Sweet, 1988
 Belodellidae Khodalevich & Tschernich, 1973 [Cambropustulidae]
 Conodonti Pander, 1856 non Branson, 1938
 Oneotodontidae Miller, 1981 [Teridontidae Miller, 1981]
 Protopanderodontida Sweet, 1988 [Panderodontida]
 ?Pronodontidae Lindström, 1970
 ?Cornuodontidae Faohraeus, 1966
 ?Protopanderodontidae Lindström, 1970 [Juanognathidae Bergström, 1981]
 ?Strachanognathidae Bergström, 1981
 ?Pseudooneotodidae
 Clavohamulidae Lindström, 1970
 Drepanoistodontidae Faohraeus, 1978
 Acanthodontidae Lindström, 1970
 Scolopodontidae Bergström, 1981
 Panderodontidae Lindström, 1970
 Prioniodontida Dzik, 1976 [Distacodontida] (paraphyletic)
 ?Acodontidae Dzik, 1993 [Tripodontinae Sweet, 1988]
 ?Cahabagnathidae Stouge & Bagnoli 1999
 ?Distacodontidae Bassler, 1925 emend. Ulrich & Bassler, 1926 [Drepanodontinae Fahraeus & Nowlan, 1978; Lonchodininae Hass, 1959]
 ?Gamachignathidae Wang & Aldridge, 2010
 ?Jablonnodontidae Dzik, 2006
 ?Nurrellidae Pomešano-Cherchi, 1967
 ?Paracordylodontidae Bergström, 1981
 ?Playfordiidae Dzik, 2002
 ?Ulrichodinidae Bergström, 1981
 Rossodus Repetski & Ethington, 1983
 Multioistodontidae Harris, 1964 [Dischidognathidae]
 Oistodontidae Lindström, 1970
 Periodontidae Lindström, 1970
 Rhipidognathidae Lindström, 1970 sensu Sweet, 1988
 Prioniodontidae Bassler, 1925
 Phragmodontidae Bergström, 1981
 Plectodinidae Sweet, 1988
 Icriodontacea
 Balognathidae (Hass, 1959)
 Polyplacognathidae Bergström, 1981
 Distomodontidae Klapper, 1981
 Icriodellidae Sweet, 1988
 Icriodontidae Müller & Müller, 1957
 Prioniodinida Sweet, 1988
 ?Oepikodontidae Bergström, 1981
 ?Xaniognathidae Sweet, 1981
 Chirognathidae Branson & Mehl, 1944
 Prioniodinidae Bassler, 1925 [Hibbardellidae Mueller, 1956]
 Bactrognathidae Lindström, 1970
 Ellisoniidae Clark, 1972
 Gondolellidae Lindström, 1970
 Ozarkodinida Dzik, 1976 [Polygnathida]
 ?Anchignathodontidae Clark, 1972
 ?Archeognathidae Miller, 1969
 ?Belodontidae Huddle, 1934
 ?Coleodontidae Branson & Mehl, 1944 [Hibbardellidae Müller, 1956; Loxodontidae]
 ?Eognathodontidae Bardashev, Weddige & Ziegler, 2002
 ?Francodinidae Dzik, 2006
 ?Gladigondolellidae (Hirsch, 1994) [Sephardiellinae Plasencia, Hirsch & Márquez-Aliaga, 2007; Neogondolellinae Hirsch, 1994; Cornudininae Orchard, 2005; Epigondolellinae Orchard, 2005; Marquezellinae Plasencia et al., 2018; Paragondolellinae Orchard, 2005; Pseudofurnishiidae Ramovs, 1977]
 ?Iowagnathidae Liu et al., 2017
 ?Novispathodontidae (Orchard, 2005)
 ?Trucherognathidae Branson & Mehl, 1944
 ?Vjalovognathidae Shen, Yuan & Henderson, 2015
 ?Wapitiodontidae Orchard, 2005
 Cryptotaxidae Klapper & Philip, 1971
 Spathognathodontidae Hass, 1959 [Ozarkodinidae Dzik, 1976]
 Pterospathodontidae Cooper, 1977 [Carniodontidae]
 Kockelellidae Klapper, 1981 [Caenodontontidae]
 Polygnathidae Bassler, 1925 [?Eopolygnathidae Bardashev, Weddige & Ziegler, 2002]
 Palmatolepidae Sweet, 1988
 Hindeodontidae (Hass, 1959)
 Elictognathidae Austin & Rhodes, 1981
 Gnathodontidae Sweet, 1988
 Idiognathodontidae Harris & Hollingsworth, 1933
 Mestognathidae Austin & Rhodes, 1981
 Cavusgnathidae Austin & Rhodes, 1981
 Sweetognathidae Ritter, 1986
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 Related pages 

 Promissum

 References 

Category:Agnatha
Category:Fossils