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Conodonts (Greek kōnos, "cone", + odont, "tooth") are extinct chordates resembling eels, classified in the

Conodonts
A conodont
Conodont elements from the Deer Valley Member of the Mauch Chunk Formation

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(conodont bearers) to avoid ambiguity.

Conodont teeth are the earliest found in the fossil record. [1]

Contents Edit

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  • 1Description
  • 2Ecology
  • 3Classification and phylogeny
  • 4Elements
  • 5See also
  • 6Notes
  • 7References
  • 8Further reading
  • 9External links

Description Edit

The 11 known fossil imprints of conodont animals record an eel-like creature with 15, or more rarely, 19 elements that form a bilaterally symmetrical array in the head. This array constituted a feeding apparatus that is radically different from the jaws of modern animals. The three forms of teeth, i.e., coniform cones, ramiform bars, and pectiniform platforms, may have performed different functions.

The organisms range from a centimeter or so[verification needed] to the large Promissum, 40 cm in length.[2] 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 is postulated to have been wiped out in the Triassic–Jurassic extinction event, which occurred roughly 200 million years ago.[3]

Ecology[edit] Edit

The "teeth" of some conodonts have been interpreted as filter-feeding apparatuses, filtering plankton from the water and passing it down the throat.[citation needed] Others have been interpreted as a "grasping and crushing array".[2] The lateral position of the eyes makes it unlikely that conodonts were active predators.[citation needed] The preserved musculature suggests that some conodonts (Promissum at least) were efficient cruisers, but incapable of bursts of speed.[2]

Classification and phylogeny[edit] Edit

As of 2012, scientists classify the conodonts in the phylum Chordata on the basis of their fins with fin rays, chevron-shaped muscles and notochord.[4]

Milsom and Rigby envision them as vertebrates similar in appearance to modern hagfish and lampreys,[5] and phylogenetic analysis suggests they are more derived than either of these groups.[6] However, this analysis comes with one caveat: early forms of conodonts, the protoconodonts, appear to form a distinct clade from the laterparaconodonts and euconodonts. Protoconodonts likely represent a stem group to the phylum that includes chaetognath worms; this conclusion suggests that chaetognaths are not close relatives of true conodonts.[7] Moreover, some analyses do not regard conodonts as either vertebrates or craniates, because they lack the main characteristics of these groups.[8]

Craniata 

Hagfish[Note 1]

Vertebrata 
Hyperoartia  Lampreys


Conodonta 

Paraconodontida



Proconodontida[Note 2]

Euconodonta[Note 3] 


Protopanderodontida


Panderontida


Prioniodontida 

Paracordylodus



Balognathidae



Prioniodinida


Ozarkodinida








Heterostracans, osteostracans and gnathostomes




Elements[edit] Edit

For many years, conodonts were known only from enigmatic tooth-like microfossils (200 micrometers to 5 millimeters in length[11]), which occur commonly, but not always in isolation, and were not associated with any other fossil. These phosphatic microfossils are now termed "conodont elements" to avoid confusion. They are widely used in biostratigraphy.

Conodont elements are also used as paleothermometers, a proxy for thermal alteration in the host rock, because under higher temperatures, the phosphate undergoes predictable and permanent color changes, measured with the conodont alteration index. This has made them useful for petroleum exploration where they are known, in rocks dating from the Cambrian to the Late Triassic.

Until the early 1980s, conodont teeth had not been found in association with fossils of the host organism, in a konservat lagerstätte.[12] This is because most of the conodont animal was soft-bodied, thus everything but the teeth was unsuited for preservation under normal circumstances.

The conodont apparatus may comprise a number of discrete elements, including the spathognathiform, ozarkodiniform, trichonodelliform, neoprioniodiform, and other forms.[13]

See also[edit] Edit

Paleontology portal
    • Lau event - mass extinction event with major impact on conodonts

Notes[edit] Edit

    1. Jump up^ Here, the hagfish are treated as a separate clade, as in Sweet and Donoghue's 2001 tree produced without cladistic analysis.[9] However, it has been recognised by some [10] that the hagfish and lampreys may be closer to one another in their own clade, the Cyclostomata.
    2. Jump up^ The clade Proconodontida is also known as Cavidonti.
    3. Jump up^ Euconodonta is referred to as "Conodonti" by Sweet and Donoghue,[9] although this is not widely used[original research?].

References[edit] Edit

    1. Jump up^ 
    2. ^ Jump up to:a b c 
    3. Jump up^ The extinction of conodonts —in terms of discrete elements— at the Triassic-Jurassic boundary
    4. Jump up^ 
    5. Jump up^ 
    6. Jump up^ 
    7. Jump up^ 
    8. Jump up^ 
    9. ^ Jump up to:a b 
    10. Jump up^ 
    11. Jump up^ 
    12. Jump up^ 
    13. Jump up^ 

Further reading[edit] Edit

    • Gould, Stephen Jay (1985). "Reducing Riddles". In The Flamingo's Smile, 245-260. New York, W.W. Norton and Company. ISBN 0-393-30375-6.
    • External link in |work= (help)
    • Knell, Simon J. The Great Fossil Enigma: The Search for the Conodont Animal (Indiana University Press; 2012) 440 pages
    • Sweet, Walter. The Conodonta.

External links[edit] Edit

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