Editing Conodont (section)

== Classification and phylogeny ==

=== Affinities ===
{{As of | 2012}}, scientists classify the conodonts in the [[Phylum (biology)|phylum]] [[Chordata]] on the basis of their fins with fin rays, [[Chevron (insignia)|chevron]]-shaped muscles and [[notochord]].<ref name="Briggs-1992">{{cite journal
  | title = Conodonts: a major extinct group added to the vertebrates
  | journal = Science
  | first = D.
  | last = Briggs
  | volume = 256
  | issue = 5061
  | pages = 1285–1286
  | date = May 1992
  | doi = 10.1126/science.1598571
  | pmid = 1598571
| bibcode = 1992Sci...256.1285B
  }}</ref>

Milsom and [[Sue Rigby|Rigby]] envision them as vertebrates similar in appearance to modern hagfish and lampreys,<ref name="Milsom-2004">{{cite book
  | last = Milsom
  | first = Clare
  | author2-last = Rigby
  | author2-first = Sue
  | author2-link = Sue Rigby
  | title = Fossils at a Glance
  | year = 2004
  | publisher = Blackwell Publishing
  | location = Victoria, Australia
  | isbn = 978-0-632-06047-4
  | page = 88
  | chapter = Vertebrates
}}</ref> and [[phylogenetic]] analysis suggests they are more [[Synapomorphy|derived]] than either of these groups.<ref name="Donoghue-2000">{{cite journal |author=Donoghue |first1=P.C.J. |last2=Forey |first2=P.L. |last3=Aldridge |first3=R.J. |year=2000 |title=Conodont affinity and chordate phylogeny |url=http://journals.cambridge.org/abstract_S0006323199005472 |journal=Biological Reviews |volume=75 |issue=2 |pages=191–251 |doi=10.1111/j.1469-185X.1999.tb00045.x |pmid=10881388 |s2cid=22803015 |access-date=}}</ref> However, this analysis comes with one caveat: the earliest conodont-like fossils, the [[protoconodont]]s, appear to form a distinct clade from the later [[Paraconodontida|paraconodonts]] and '''euconodonts'''. Protoconodonts are probably not relatives of true conodonts, but likely represent a stem group to [[Chaetognatha]], an unrelated phylum that includes arrow worms.<ref name="Szaniawski, H.-2002">{{cite journal
 | author = Szaniawski, H.
 | year = 2002
 | title = New evidence for the protoconodont origin of chaetognaths
 | journal = Acta Palaeontologica Polonica
 | volume = 47
 | issue = 3
 | pages = 405
 | url = http://app.pan.pl/archive/published/app47/app47-405.pdf
}}</ref>

Moreover, some analyses do not regard conodonts as either [[vertebrate]]s or [[Craniata|craniates]], because they lack the main characteristics of these groups.<ref name="Nowlan-2010">{{cite journal
 | author = Turner, S., Burrow, C.J., Schultze, H.P., Blieck, A., Reif, W.E., Rexroad, C.B., Bultynck, P., Nowlan, G.S.
 | year = 2010
 | title = False teeth: conodont-vertebrate phylogenetic relationships revisited
 | journal = Geodiversitas
 | volume = 32
 | issue = 4
 | pages = 545–594
 | url = http://www.mnhn.fr/museum/front/medias/publication/31374_g2010n4a1.pdf
 | doi = 10.5252/g2010n4a1
 | last2 = Burrow
 | last3 = Schultze
 | last4 = Blieck
 | last5 = Reif
 | last6 = Rexroad
 | last7 = Bultynck
 | last8 = Nowlan
 | s2cid = 86599352
 | access-date = 2011-02-11
 | archive-url = https://web.archive.org/web/20120319203153/http://www.mnhn.fr/museum/front/medias/publication/31374_g2010n4a1.pdf
 | archive-date = 2012-03-19
 | url-status = dead
 }}</ref> More recently it has been proposed that conodonts may be stem-[[Cyclostomi|cyclostomes]], more closely related to [[hagfish]] and [[lamprey]]s than to [[Gnathostomata|jawed vertebrates]], based on similarities in the shape of their fins, and the idea that the conodont elements may be [[Homology (biology)|homologous]] with lamprey and hagfish tooth plates.<ref>{{Cite journal|last1=Miyashita|first1=Tetsuto|last2=Coates|first2=Michael I.|last3=Farrar|first3=Robert|last4=Larson|first4=Peter|last5=Manning|first5=Phillip L.|last6=Wogelius|first6=Roy A.|last7=Edwards|first7=Nicholas P.|last8=Anné|first8=Jennifer|last9=Bergmann|first9=Uwe|last10=Palmer|first10=A. Richard|last11=Currie|first11=Philip J.|date=2019-02-05|title=Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny|journal=Proceedings of the National Academy of Sciences|language=en|volume=116|issue=6|pages=2146–2151|doi=10.1073/pnas.1814794116|issn=0027-8424|pmc=6369785|pmid=30670644|bibcode=2019PNAS..116.2146M|doi-access=free}}</ref>

=== Ingroup relations ===
Individual conodont elements are difficult to classify in a consistent manner, but an increasing number of conodont species are now known from multi-element assemblages, which offer more data to infer how different conodont lineages are related to each other. The following is a simplified cladogram based on Sweet and Donoghue (2001),<ref name="Sweet-2001" /> which summarized previous work by Sweet (1988)<ref name="Sweet-1988" /> and Donoghue et al. (2000):<ref name="Donoghue-2000" />

{{clade| style=font-size:95%;line-height:80%
| label1=
| 1={{clade
|1= [[Paraconodontida]]
| label2= {{extinct}}'''Conodonta'''
| 2={{clade
| 1= [[Cavidonti]] / [[Proconodontida]]
| label2=[[Conodonti]]
| 2={{clade
| 1={{clade
| 1= [[Protopanderodontida]]
| 2= [[Panderontida]]}}
| label2=[[Prioniodontida]]
| 2={{clade
| 1= ''[[Paracordylodus]]''
| 2={{clade
| 1= [[Balognathidae]]
| 2={{clade
| 1= [[Prioniodinida]]
| 2= [[Ozarkodinida]]
}}
}}
}}
}}
 }} }} }}Only a few studies approach the question of conodont ingroup relationships from a [[Cladistics|cladistic]] perspective, as informed by [[phylogenetic analyses]]. One of the broadest studies of this nature was the analysis of Donoghue et al. (2008), which focused on "complex" conodonts (Prioniodontida and other descendant groups):<ref name="Donoghue-2008" />