Dictionary:
co·no·dont (kō'nə-dŏnt', kŏn'ə-)  |
[Greek kōnos, cone + -ODONT.]
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A group of extinct marine animals that are often abundant in strata of Late Cambrian to Late Triassic age, a time span of about 300 million years. Only the mineralized elements, which are usually 0.2 to 2 mm (0.008 to 0.08 in.) in dimension (the largest known reach 14 mm or 0.6 in.), are normally preserved. They are routinely extracted as isolated discrete specimens by chemical degradation of the rock in which they occur. In the earliest euconodonts (“true” conodonts, as opposed to the more primitive, and possibly unrelated, protoconodonts and paraconodonts), the elements comprise an upper crown and a basal body. The basal body occupies a cavity in the base of the crown, but is not present in the majority of post-Devonian species. In advanced conodonts the crown incorporates regular patches of opaque, finely crystalline, white matter.
For many years, conodont taxonomists treated individual element types as separate species. There are three major shape categories, coniform, ramiform, and pectiniform (see illustration). Coniform elements were dominant in the Cambrian to Early Ordovician and common until the Devonian. Ramiform (comblike) elements extend into elongate processes with various arrangements of denticles. Pentiniform elements include straight and arched blades, and may be expanded laterally to form a platform.
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Conodont elements: (a, b) coniform elements, (c, d) ramiform elements, (e, f) pectiniform blade elements, (g, h) pectiniform platform elements, (i) bedding-plane assemblage.
In the absence of preserved soft parts, the nature of the affinities of conodonts was the subject of considerable speculation and debate. Since the first discovery of isolated elements in 1856, conodonts have been variously aligned with algae, higher plants, several wormlike phyla, mollusks, arthropods, lophophorates, chaetognaths, and chordates, or have been assigned to a separate phylum, Conodonta. It was not until 1983 that evidence of the soft parts was described by D. E. G. Briggs, E. N. K. Clarkson, and R. J. Aldridge, on the basis of the first of several specimens discovered in lower Carboniferous rocks near Edinburgh, Scotland. The evidence of the soft-part morphology indicates that the conodonts belong within the chordates; it is no longer possible to justify their separation as a phylum, Conodonta. See also Chordata.
Although the biological affinities of conodonts and the function of the elements were essentially unknown until recently, they have nonetheless been extensively studied because of their important geological applications. Most significant of these is the use of conodont elements in biostratigraphy. See also Stratigraphy.
| Britannica Concise Encyclopedia: conodont |
For more information on conodont, visit Britannica.com.
| WordNet: conodont |
The noun has 2 meanings:
Meaning #1:
tiny fossil cone-shaped tooth of the most primitive vertebrate: the conodont
Meaning #2:
small (2 in) extinct eellike fish with a finned tail and a notochord and having cone-shaped teeth containing cellular bone; late Cambrian to late Triassic; possible predecessor of the cyclostomes
| Wikipedia: Conodont |
| Conodonts Fossil range: 495–199.6 Ma Late Cambrian to Late Triassic |
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 Reconstruction of a Conodont
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Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. The animals are also called Conodontophora (conodont bearers) to avoid ambiguity.
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The eleven known fossil imprints of conodont animals depict an eel-like creature with 15 or, more rarely, 19 elements forming a bilaterally symmetrical array in the head. This array constituted a feeding apparatus radically 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[verification needed] to the giant Promissum, 40 cm in length.[1] It is now widely agreed that conodonts had large eyes, fins with fin rays, chevron-shaped muscles and a notochord.
The "teeth" of some conodonts have been interpreted as filter-feeding apparatuses, filtering out plankton from the water and passing it down the throat.[citation needed] Others have been interpreted as a "grasping and crushing array".[1]
The lateral position of the eyes makes a predatory role unlikely.[citation needed]
The preserved musculature hints that some conodonts (Promissum at least) were efficient cruisers but incapable of bursts of speed.[1]
The conodonts are currently classified in the phylum Chordata because their fins with fin rays, chevron-shaped muscles and notochord are characteristic of Chordata.[2]
They are considered by Milsom and Rigby to be vertebrates similar in appearance to modern hagfish and lampreys,[3] and phylogenetic analysis suggests that they are more derived than either of these groups.[4] This analysis, however, comes with one caveat: early forms of conodonts, the protoconodonts, appear to form a distinct clade from the later paraconodonts and euconodonts. It appears likely that the protoconodonts represent a stem group to the phylum containing chaetognath worms, indicating that they are not close relatives of true conodonts.[5]
For many years, conodonts were known only from enigmatic tooth-like microfossils, 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. This confusion is most apparent for the non-specialist in the book "Your Inner Fish", by Neil Shubin, who describes the origin of teeth in chapter 4. In this chapter, the author attaches the name "conodont" to both the "conodont bearer" (the animal) and the "conodont elements" (the teeth), and the reader may have a hard time to make sense of the concept of "animals living in the mouths of animals".
They are widely used in biostratigraphy.
Conodont elements are also used as paleothermometers, a proxy for thermal alteration in the host rock. This is 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.
It was not until early 1980s that the conodont teeth were found in association with fossils of the host organism, in a konservat lagerstätte.[6] This is because most of the conodont animal was soft-bodied, thus everything but the teeth were not suited for preservation under normal circumstances.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
 | Jawless vertebrates |
| Hindeodus parvus |
| Promissum |
 | How are lampreys like extinct conodonts? |
| What do Hagfishes and Lampreys have in common with the extinct conodonts? |
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more |
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| WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Conodont". Read more |
