Conodont

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

Conodonts are considered index fossils, fossils used to define and identify geological periods.

Conodonts
Temporal range: Cambrian to Late Triassic (Rhaetian)
ConodontZICA
Reconstruction of a conodont
Euconodonta
Two conodont "teeth" and a reconstruction of a conodont
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Conodonta
Eichenberg 1930[1]
Groups
  • Paraconodonta
    • Amphigeisiniformes
    • Westergaardodiniformes
  • Euconodonta
Synonyms
  • Conodontophorida (otherwise an order according to Sepkoski, 2002[2])

Geological history

The conodonts first appeared during the Cambrian Stage 2 (also referred as Tommotian).[3] The still unnamed Cambrian Stage 10 can be defined as the first appearance of Eoconodontus notchpeakensis. The upper boundary is defined as the appearance of Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 ± 1.9 million years ago.

The Cambrian–Ordovician extinction event occurred approximately 488 million years ago. This early Paleozoic extinction event extirpated many conodonts.

The Lau event, about 420 million years ago, a relatively minor mass extinction during the Silurian period, had a major impact on conodont populations.

The Kačák Event was a period of significant extinctions. The group most affected was the Ammonoidea, although there were also faunal turnovers amongst conodonts and dacryoconarids.[4]

The entire class is postulated to have been wiped out in the Triassic–Jurassic extinction event, which occurred roughly 200 million years ago.[5] Near the end of the Triassic deadly marine biocalcification began to occur, along with oceanic acidification, sea-level fluctuations and the Central Atlantic Magmatic Province (CAMP) releasing carbon dioxide, sulfur dioxide and aerosols. These environmental catastrophes caused the extinction of the conodonts, along with 34% of other marine genera.[6]

The discovery of conodonts

Conodonts were first discovered by Heinz Christian Pander, the results published, in Saint Petersburg, Russia, in 1856.[7] The name pander is a common part, in scientific names of conodonts.

Description

Promissum NT small
Life restoration of Promissum pulchrum

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.

The organisms range from a centimeter or so to 40 cm (Promissum) in length.[8] It is now widely agreed that conodonts had large eyes, fins with fin rays, chevron-shaped muscles and a notochord.

Elements

Conodonts
Conodont elements from the Deer Valley Member of the Mauch Chunk Formation in Pennsylvania, Maryland, and West Virginia, USA
detail
Figures 1, 2. Conodonts from the Deer Valley Member of the Mauch Chunk Formation, Keystone quarry, Pa. This collection (93RS–79c) is from the lower 10 cm of the Deer Valley Member. Note the nonabraded, although slightly broken, conodont elements of the high-energy oolitic marine facies of the Deer Valley Member.
1. Kladognathus sp., Sa element, posterior view, X140 2. Cavusgnathus unicornis, gamma morphotype, Pa element, lateral view, X140
3–9. Conodonts from the uppermost Loyalhanna Limestone Member of the Mauch Chunk Formation, Keystone quarry, Pa. This collection (93RS–79b) is from the upper 10 cm of the Loyalhanna Member. Note the highly abraded and reworked aeolian forms.
3, 4. Kladognathus sp., Sa element, lateral views, X140
5. Cavusgnathus unicornis, alpha morphotype, Pa element, lateral view, X140
6, 7. Cavusgnathus sp., Pa element, lateral view, X140
8. Polygnathus sp., Pa element, upper view, reworked Late Devonian to Early Mississippian morphotype, X140
9. Gnathodus texanus?, Pa element, upper view, X140
10–14. Conodonts from the basal 20 cm of the Loyalhanna Limestone Member of the Mauch Chunk Formation, Keystone quarry, Pa. (93RS–79a), and Westernport, Md. (93RS–67), note the highly abraded and reworked aeolian forms
10. Polygnathus sp., Pa element, upper view, reworked Late Devonian to Early Mississippian morphotype, 93RS–79a, X140
11. Polygnathus sp., Pa element, upper view, reworked Late Devonian to Early Mississippian morphotype, 93RS–67, X140
12. Gnathodus sp., Pa element, upper view, reworked Late Devonian(?) through Mississippian morphotype, 93RS–67, X140
13. Kladognathus sp., M element, lateral views, 93RS–67, X140
14. Cavusgnathus sp., Pa element, lateral view, 93RS–67, X140

Conodont teeth are the earliest found in the fossil record.[9] The evolution of mineralized tissues has been puzzling for more than a century. It has been hypothesized that the first mechanism of mammalian tissue mineralization began either in the oral skeleton of conodont or the dermal skeleton of early agnathans.

The element array constituted a feeding apparatus that is radically different from the jaws of modern animals. They are now termed "conodont elements" to avoid confusion. The three forms of teeth, i.e., coniform cones, ramiform bars, and pectiniform platforms, probably performed different functions.

For many years, conodonts were known only from enigmatic tooth-like microfossils (200 micrometers to 5 millimeters in length[10]), which occur commonly, but not always in isolation, and were not associated with any other fossil. Until the early 1980s, conodont teeth had not been found in association with fossils of the host organism, in a konservat lagerstätte.[11] This is because the conodont animal was soft-bodied, thus everything but the teeth was unsuited for preservation under normal circumstances.

These microfossils are made of hydroxylapatite (a phosphatic mineral).[12] The conodont elements can be extracted from rock using adequate solvents.[13][14][15]

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.

Multielement conodonts

Manticolepis subrecta
Model of elements of Manticolepis subrecta - a conodont from the Upper Frasnian of Poland - photography taken in the Geological Museum of the Polish Geological Institute in Warsaw

The conodont apparatus may comprise a number of discrete elements, including the spathognathiform, ozarkodiniform, trichonodelliform, neoprioniodiform, and other forms.[16]

In the 1930s, the concept of conodont assemblages was described by Hermann Schmidt[17] and by Harold W. Scott in 1934.[18][19][20][21]

Elements of ozarkodinids

The feeding apparatus of ozarkodinids is composed at the front of an axial Sa element, flanked by two groups of four close-set elongate Sb and Sc elements which were inclined obliquely inwards and forwards. Above these elements lay a pair of arched and inward pointing (makellate) M elements. Behind the S-M array lay transversely oriented and bilaterally opposed (pectiniform, i.e. comb-shaped) Pb and Pa elements.[22]

Ecology

The "teeth" of some conodonts have been interpreted as filter-feeding apparatuses, filtering plankton from the water and passing it down the throat. Others have been interpreted as a "grasping and crushing array".[8] The lateral position of the eyes makes it unlikely that conodonts were active predators. The preserved musculature suggests that some conodonts (Promissum at least) were efficient cruisers, but incapable of bursts of speed.[8]

A study on the population dynamics of Alternognathus has been published. Among other things, it demonstrates that at least this taxon had short lifespans lasting around a month.[23]

Classification and phylogeny

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.[24]

Milsom and Rigby envision them as vertebrates similar in appearance to modern hagfish and lampreys,[25] and phylogenetic analysis suggests they are more derived than either of these groups.[26] However, this analysis comes with one caveat: early forms of conodonts, the protoconodonts, appear to form a distinct clade from the later paraconodonts 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.[27] Moreover, some analyses do not regard conodonts as either vertebrates or craniates, because they lack the main characteristics of these groups.[28]

 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

Taxonomy

Conodonta taxonomy based on Sweet & Donoghue [29][31], Mikko's Phylogeny Archive[32] and Fish classification 2017.[33]

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

  • Paraconodonta Müller 1962 [Paraconodontida]
  • Conodontophora Eichenberg 1930
    • Caviodonti Sweet 1988
      • Proconodontiformes Sweet 1988
        • Pseudooneotodidae Wang & Aldridge 2010
        • Proconodontidae Lindström 1981
        • Cordylodontidae Lindström 1970 [Cyrtoniodontinae Hass 1959]
        • Fryxellodontina
        • 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 Faohraeus1966
        •  ?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
        • 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

See also

Notes

  1. ^ Here, the hagfish are treated as a separate clade, as in Sweet and Donoghue's 2001 tree produced without cladistic analysis.[29] However, it has been recognised by some [30] that the hagfish and lampreys may be closer to one another in their own clade, the Cyclostomata.
  2. ^ The clade Proconodontida is also known as Cavidonti.
  3. ^ Euconodonta is referred to as "Conodonti" by Sweet and Donoghue,[29] although this is not widely used.

References

  1. ^ Conodonten aus dem Culm des Harzes. W Eichenberg, Paläontologische Zeitschrift, 1930, page 177-182, doi:10.1007/BF03044446
  2. ^ J. J. Sepkoski. 2002. A compendium of fossil marine animal genera. Bulletins of American Paleontology 363:1-560
  3. ^ Early Cambrian (Tommotian) conodonts and other shelly microfauna from the Upper Krol of Mussoorie Syncline. RJ Azmi, VP Pancholi, Lesser Himalaya, with remarks on the Precambrian, 1983
  4. ^ DeSantis, M.K.; Brett C.E. (2011). "Late Eifelian (Middle Devonian) biocrises: Timing and signature of the pre-Kačák Bakoven and Stony Hollow Events in eastern North America". Palaeogeography, Palaeoclimatology, Palaeoecology. 304 (1–2): 113–135. doi:10.1016/j.palaeo.2010.10.013. Retrieved 4 March 2012.
  5. ^ The extinction of conodonts —in terms of discrete elements— at the Triassic-Jurassic boundary
  6. ^ Graham Ryder; David E. Fastovsky; Stefan Gartner (1996). The Cretaceous-Tertiary Event and Other Catastrophes in Earth History. Geological Society of America. p. 19. ISBN 9780813723075.
  7. ^ Sweet, Walter C.; Cooper, Barry J. (December 2008). "C.H. Pander's introduction to conodonts, 1856". C.H. Pander's introduction to conodonts, 1856. researchgate.net. Retrieved 3 January 2019.CS1 maint: Multiple names: authors list (link)
  8. ^ a b c Gabbott, S.E.; R. J. Aldridge; J. N. Theron (1995). "A giant conodont with preserved muscle tissue from the Upper Ordovician of South Africa". Nature. 374 (6525): 800–803. Bibcode:1995Natur.374..800G. doi:10.1038/374800a0.
  9. ^ Shubin, Neil (2009). Your Inner Fish: A Journey into the 3.5 Billion Year History of the Human Body (reprint ed.). New York: Pantheon Books. pp. 85–86. ISBN 9780307277459.
  10. ^ MIRACLE. "Conodonts". Retrieved 26 August 2014.
  11. ^ Briggs, D. E. G.; Clarkson, E. N. K.; Aldridge, R. J. (1983). "The conodont animal". Lethaia. 16 (1): 1–14. doi:10.1111/j.1502-3931.1983.tb01993.x.
  12. ^ Chemical systematics of conodont apatite determined by laser ablation ICPMS. Julie A. Trotter and Stephen M. Eggins, Chemical Geology, Volume 233, Issues 3–4, 15 October 2006, Pages 196–216, doi:10.1016/j.chemgeo.2006.03.004
  13. ^ A Buffered Formic Acid Technique for Conodont Extraction. Lennart Jeppsson and Rikard Anehus, Journal of Paleontology, Vol. 69, No. 4 (Jul., 1995), pages 790-794 (Stable URL)
  14. ^ Extraction Techniques for Phosphatic Fossils. Owen R. Green in A Manual of Practical Laboratory and Field Techniques in Palaeobiology. pages 318-330, doi:10.1007/978-94-017-0581-3_27
  15. ^ Effects of extraction protocols on the oxygen isotope composition of conodont elements. Page C. Quinton, Stephen A. Leslie, Achim D. Herrmann and Kenneth G. MacLeod, Chemical Geology, Volume 431, 1 August 2016, Pages 36–43, doi:10.1016/j.chemgeo.2016.03.023
  16. ^ Bergström, S. M.; Carnes, J. B.; Ethington, R. L.; Votaw, R. B.; Wigley, P. B. (1974). "Appalachignathus, a New Multielement Conodont Genus from the Middle Ordovician of North America". Journal of Paleontology. 48 (2): 227–235. Bibcode:1974JPal...48..524M. doi:10.2307/1303249 (inactive 2018-09-26). JSTOR 1303249.
  17. ^ Conodonten-Funde in ursprünglichem Zusammenhang. Hermann Schmidt, Paläontologische Zeitschrift, 1934, volume 16, Issue 1-2 , pages 76-85, doi:10.1007/BF03041668
  18. ^ The Zoological Relationships of the Conodonts. Harold W. Scott, Journal of Paleontology, Vol. 8, No. 4 (Dec., 1934), pages 448-455 (Stable URL)
  19. ^ Conodont Assemblages from the Heath Formation, Montana. Harold W. Scott, Journal of Paleontology, Vol. 16, No. 3 (May, 1942), pages 293-300 (Stable URL)
  20. ^ Late Mississippian conodonts from the Bird Spring Formation in Nevada. David L. Dunn, Journal of Paleontology, November 1965, volume 39, issue 6 (abstract)
  21. ^ A Questionable Natural Conodont Assemblage from Middle Ordovician Limestone, Ottawa, Canada. Christopher R. Barnes, Journal of Paleontology, Vol. 41, No. 6 (Nov., 1967), pages 1557-1560 (Stable URL)
  22. ^ Purnell, M. A.; Donoghue, P. C. (1997). "Architecture and functional morphology of the skeletal apparatus of ozarkodinid conodonts". Philosophical Transactions of the Royal Society B: Biological Sciences. 352 (1361): 1545–1564. doi:10.1098/rstb.1997.0141. PMC 1692076.
  23. ^ Przemysław Świś (2019). "Population dynamics of the Late Devonian conodont Alternognathus calibrated in days". Historical Biology: An International Journal of Paleobiology. in press. doi:10.1080/08912963.2018.1427088.
  24. ^ Briggs, D. (May 1992). "Conodonts: a major extinct group added to the vertebrates". Science. 256 (5061): 1285–1286. Bibcode:1992Sci...256.1285B. doi:10.1126/science.1598571. PMID 1598571.
  25. ^ Milsom, Clare; Rigby, Sue (2004). "Vertebrates". Fossils at a Glance. Victoria, Australia: Blackwell Publishing. p. 88. ISBN 978-0-632-06047-4.
  26. ^ Donoghue, P.C.J.; Forey, P.L.; Aldridge, R.J. (2000). "Conodont affinity and chordate phylogeny". Biological Reviews. 75 (2): 191–251. doi:10.1111/j.1469-185X.1999.tb00045.x. PMID 10881388. Retrieved 2008-04-07.CS1 maint: Multiple names: authors list (link)
  27. ^ Szaniawski, H. (2002). "New evidence for the protoconodont origin of chaetognaths" (PDF). Acta Palaeontologica Polonica. 47 (3): 405.
  28. ^ Turner, S., Burrow, C.J., Schultze, H.P., Blieck, A., Reif, W.E., Rexroad, C.B., Bultynck, P., Nowlan, G.S.; Burrow; Schultze; Blieck; Reif; Rexroad; Bultynck; Nowlan (2010). "False teeth: conodont-vertebrate phylogenetic relationships revisited" (PDF). Geodiversitas. 32 (4): 545–594. doi:10.5252/g2010n4a1.CS1 maint: Multiple names: authors list (link)
  29. ^ a b c Sweet, W. C.; Donoghue, P. C. J. (2001). "CONODONTS: PAST, PRESENT, FUTURE". Journal of Paleontology. 75 (6): 1174–1184. Bibcode:1974JPal...48..524M. doi:10.1666/0022-3360(2001)075<1174:CPPF>2.0.CO;2.
  30. ^ Bourlat, S. J; T. Juliusdottir, C. J Lowe, R. Freeman, J. Aronowicz, M. Kirschner, E. S Lander, M. Thorndyke, H. Nakano, A. B Kohn, others (2 November 2006). "Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida". Nature. 444 (7115): 85–88. Bibcode:2006Natur.444...85B. doi:10.1038/nature05241. ISSN 0028-0836. PMID 17051155.CS1 maint: Multiple names: authors list (link)
  31. ^ Sweet, W. C. (1988). "The Conodonta: morphology, taxonomy, paleoecology and evolutionary history of a long-extinct animal phylum". Oxford Monographs on Geology and Geophysics (10): 1–211.
  32. ^ Mikko's Phylogeny Archive [1] Haaramo, Mikko (2007). "Conodonta - conodonts". Retrieved 2015-12-30.
  33. ^ "Fish classification 2017". mayatan.web.fc2.com. Retrieved 2018-12-27.

Further reading

  • Aldridge, R. J.; Briggs, D. E. G.; Smith, M. P.; Clarkson, E. N. K.; Clark, N. D. L. (1993). "The anatomy of conodonts". Philosophical Transactions of the Royal Society of London, Series B. 340 (1294): 405–421. doi:10.1098/rstb.1993.0082.
  • Aldridge, R. J.; Purnell, M. A. (1996). "The conodont controversies". Trends in Ecology and Evolution. 11 (11): 463–468. doi:10.1016/0169-5347(96)10048-3. PMID 21237922.
  • Donoghue, P. C. J.; Forey, P. L.; Aldridge, R. J. (2000). "Conodont affinity and chordate phylogeny". Biological Reviews. 75 (2): 191–251. doi:10.1111/j.1469-185X.1999.tb00045.x. PMID 10881388.
  • 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.
  • Janvier, P (1997). "Euconodonta". The tree of life web project. Retrieved 2007-09-05.
  • Knell, Simon J. The Great Fossil Enigma: The Search for the Conodont Animal (Indiana University Press; 2012) 440 pages
  • Sweet, Walter. The Conodonta.
  • Sweet, W. C.; Donoghue, P. C. J. (2001). "Conodonts: past, present and future". Journal of Paleontology. 75 (6): 1174–1184. Bibcode:1974JPal...48..524M. doi:10.1666/0022-3360(2001)075<1174:CPPF>2.0.CO;2. ISSN 0022-3360.
  • A suprageneric taxonomy of the conodonts. Maurits Lindström, Lethaia, Volume 3, Issue 4, pages 427–445, October 1970, doi:10.1111/j.1502-3931.1970.tb00834.x

External links

Acodus

Acodus is an extinct genus of conodonts.

Amorphognathus

Amorphognathus is an extinct conodont genus in the family Balognathidae from the Ordovician.

Balognathidae

Balognathidae is an extinct conodont family.

Cambrian Stage 10

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 (see below). 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.

Gnathodus

Gnathodus is an extinct conodont genus in the family Idiognathodontidae.

Icriodus

Icriodus is an extinct conodont genus in the family Gnathodontidae.

In 1938, Edward Branson and Maurice Mehl reviewed the conodont genus Icriodus.

Idiognathodus

Idiognathodus is an extinct conodont genus in the family Idiognathodontidae.

Maurice Mehl

Maurice Goldsmith Mehl (born 1887 in Burlingame, Kansas, died in 1966 in Columbia, Missouri) was an American paleontologist.

Neogondolella

Neogondolellla is an extinct genus of conodonts. Neogondolela regalis was re-evaluated in 2018 by Martyn Lee Golding.

Oulodus

Oulodus is a genus of conodonts in the family Prioniodinidae.

O. elegans is found in the Late Silurian to Early Devonian Keyser Formation, a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.

Ozarkodina

Ozarkodina is an extinct genus of conodonts in the family Spathognathodontidae.

Ozarkodinida

Ozarkodinida is an extinct conodont order. It is part of the clade Prioniodontida, also known as the "complex conodonts". There are two suborders of Ozarkodinida : Prioniodinina and Ozarkodinina.

Pander Society

The Pander Society is an informal organisation founded in 1967 for the promotion of the study of conodont palaeontology. It publishes an annual newsletter. Although there are regular meetings of the Pander Society, at the Annual Meeting of the Geological Society of America, at European Conodont Symposia (ECOS for short), and elsewhere, any meeting of three or more "Panderers" is considered an official meeting of the "Pander Society". The society is headed by the Chief Panderer, currently Maria Cristina Perri of the Università di Bologna. The society confers two awards, the Pander Medal for a lifetime of achievement in conodont palaeontology, and the Hinde Medal for an outstanding contribution to conodont palaeontology by a young Panderer.Heinz Christian Pander (1794–1865) is credited as the first scientist to describe primitive creatures known as conodonts.

Paraconodontida

Paraconodontida is an extinct order of conodonts. It contains two superfamilies, Amphigeisinoidea and Furnishinoidea.

Polygnathus

Polygnathus is an extinct genus of conodonts.

Prioniodontida

Prioniodontida, also known as the "complex conodonts", is a large clade of conodonts that includes two major evolutionary grades; the Prioniodinina and the Ozarkodinina. It includes many of the more famous conodonts, such as the giant ordovician Promissum (Prioniodinina) from the Soom Shale and the Carboniferous specimens from the Granton Shrimp bed (Ozarkodinina). They are euconodonts, in that their elements are composed of two layers; the crown and the basal body, and are assumed to be a clade.

Spathognathodus

Spathognathodus is an extinct conodont genus in the family Spathognathodontidae. It is a non Platform conodont, from the Pennsylvanian (Caboniferous).

Tremadocian

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 GSSP section on Newfoundland.

Wurmiella

Wurmiella is an extinct conodont genus.Wurmiella excavata is from the Lower Devonian of Nevada.

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