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#REDIRECT [[Artiodactyl]]
{{Taxobox

| name = Cetartiodactyls
{{Redirect category shell|1=
| image = Pakicetus BW.jpg
{{R from merge}}
| image_width = 245px
{{R with Wikidata item}}
| image_caption = A restoration of ''[[Pakicetus]]'', an ancient Cetartiodactyl | fossil_range = late [[Paleocene]] - Recent
{{R from scientific name|mammal}}
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Mammalia]]
| infraclassis = [[Eutheria]]
| superordo = [[Laurasiatheria]]
| unranked_familia = '''Cetartiodactyla'''
| subdivision_ranks = Clades
| subdivision =
*[[Tylopoda]]
*'''Artiofabula'''
**[[Suina]]
**[[Cetruminantia]]
***[[Ruminantia]]
***[[Cetancodonta]]
****[[Hippopotamidae]]
****[[Cetacea]]
}}
}}
{{Taxonbar|from=Q27850}}
'''Cetartiodactyla''' is the [[clade]] in which [[whale]]s (including [[dolphin]]s) and [[even-toed ungulate]]s have currently been placed. The term was coined by merging the name for the two orders, [[Cetacea]] and [[Artiodactyla]], into a single word. The term Cetartiodactyla reflects the idea that whales evolved within the artiodactyls. Under this definition, their closest living land relative is thought to be the [[hippopotamus]]. The clade formed by uniting whales and hippos is called [[Whippomorpha]].<ref name="plosone.org">{{cite journal |title=Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution. |journal=PLOS ONE |year=2009 |last1= Spaulding |first1=M. |last2=O'Leary |first2=MA. |last3=Gatesy |first3=J. |DOI=10.1371/journal.pone.0007062 |url=http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007062}}</ref> Alternatively, the term 'Cetartiodactyla' is used to denote a clade where Cetacea evolved alongside Artiodactyla and not within it. Under this definition, all artiodactyls, including hippos, are more closely related to one another than any are to the whales.

This group has been proposed as a new order, and the merger between the two orders [[Cetacea]] and [[Artiodactyla]] is supported by the [[IUCN]] Cetacean Specialist Group <ref>http://www.iucn-csg.org/index.php/taxonomy/</ref> and by Taxonomy Committee <ref>http://www.marinemammalscience.org/index.php?option=com_content&view=article&id=758&Itemid=340</ref> of the [[Society for Marine Mammalogy]], the largest international association of marine mammal scientists in the world. Use of Order Cetartiodactyla, instead of [[Cetacea]] with Suborders Odontoceti and Myticeti, is favored by most evolutionary mammalogists working with molecular data.<ref name="plosone.org"/><ref>{{cite journal |title=The phylogeny of Cetartiodactyla: the importance of dense taxon sampling, missing data, and the remarkable promise of cytochrome b to provide reliable species-level phylogenies. |journal=Mol Phylogenet Evol. |year=2008 |last1=Agnarsson |first1=I. |last2=May-Collado |first2=LJ. |volume=48 |issue=3 |pages=964–985 |url=http://www.ncbi.nlm.nih.gov/pubmed/18590827}}</ref><ref>{{cite journal |title=A complete phylogeny of the whales, dolphins and even-toed hoofed mammals (Cetartiodactyla). |journal=Biol Rev Camb Philos Soc. |year=2005 |last1=Price |first1=SA. |last2=Bininda-Emonds |first2=OR. |last3=Gittleman |first3=JL. |volume=80 |issue=3 |pages=445–473 |url=http://www.ncbi.nlm.nih.gov/pubmed/16094808}}</ref><ref>{{cite journal |title=Phylogenetic relationships of artiodactyls and cetaceans as deduced from the comparison of cytochrome b and 12S RNA mitochondrial sequences. |journal=Molecular Biology and Evolution |year=1997 |last1=Montgelard |first1=C. |last2=Catzeflis |first2=FM. |last3=Douzery |first3=E. |volume=14 |pages=550–559 |url=http://mbe.oxfordjournals.org/content/14/5/550.short}}</ref>

Whales evolved from land [[mammal]]s and appear to form a [[monophyletic]] group. It is well accepted that all whales evolved from a single ancestor. The most widely accepted hypothesis before the 1990s was the closest relatives to whales were the fossil group [[Mesonychia]]. These were [[hoof|hooved]], predominantly [[carnivorous]] mammals known only from [[fossil]]s. But, today{{vague|date=February 2014}} few authorities still consider mesonychids to be more closely related to whales than artiodactyls. Instead, they are usually considered to be the closest relative of the Cetartiodactyla as a whole.

==Kin to hippos==
[[Image:Cladogram of Cetacea within Artiodactyla.png|thumb|left|Cladogram showing relations within Artiodactylamorpha]]
[[Image:Humpback stellwagen edit.jpg|thumb|[[Humpback whale]] breaching]]
[[Image:hippo pod.jpg|thumb|Pod of [[hippopotamus]]es, Luangwa Valley, Zambia]]

The idea that whales evolved from within the Artiodactyla is based on analysis of [[DNA]] sequences. In the initial molecular analyses, whales were shown to be more closely related to [[ruminant]]s (such as [[cattle]] and [[deer]]) than ruminants are to [[pig]]s. For the order name to reflect a real evolutionary unit, the term Cetartiodactyla was coined.

Later molecular analyses included a wider sampling of artiodactyls and produced a more complete tale. Hippos were determined to be the closest living relative of whales, ruminants were related to a whale/hippo clade, and pigs were more distant. In addition to producing the controversial whale/hippo clade, these analyses debunked the idea that hippos and pigs are closely related. This had been a popular taxonomic hypothesis ([[Suiformes]]) based on similarities in [[morphology (biology)|morphological]] (physical) characteristics.

In addition to DNA and [[protein]] sequences, researchers tracked the movement of [[transposon]]s called [[SINE]]s in the [[genome]] (see the method at [[retrotransposon marker]]). A transposon is a DNA sequence that will occasionally make a copy of itself and insert that copy into another part of the genome. It is considered highly unlikely that SINEs will insert themselves into exactly the same part of a genome by chance. The data indicate several transposons inserted themselves at the same point in the genomes of whales, ruminants and hippos (sometimes referred to as "pseudoruminants" because, although they have four-chambered stomachs like true ruminants, they do not chew the cud). This insertion point is not shared with [[camel]]s and pigs.

This hypothesis has been tested with DNA sequences from a host of genes: the complete [[mitochondrial genome]] (as well as several of its genes independently), [[beta-casein]], [[kappa-casein]], [[von Willebrand factor]], [[breast cancer 1]], [[recombination activating gene]]s 1 and 2, [[cannabinoid receptor]] 1, and several others. These sequence data and the transposons converge on the same conclusion that hippos and whales are more closely related to one another than either is to other artiodactyls.

Sequences analyzed in combined analyses with morphological characters have also produced the same results as sequences alone. Some have argued that the sheer number of characters (one for each [[nucleotide]]) in sequences swamps out the effects of morphology. A few morphology-based studies have suggested (weakly) the same results as the molecular results, but, overall, most morphological studies have conflicted with the whale/hippo hypothesis of Cetartiodactyla.

An important exception is a study conducted by Boisserie et al. (2005). They examined 80 hard morphological characters of fossil and extant cetartiodactylan taxa. Their results suggest that the hippopotamids evolved from within a clade of [[anthracothere]]s. That anthracothere/hippopotamid clade appears to be sister to the Cetacea and supports the molecular results.

==A clade apart==

The morphology and [[paleontology]]-based opinion of the relationship of whales to other mammals has also undergone considerable changes since the early 1990s. Fossils, such as ''[[Rodhocetus]]'', have been discovered that refute the notion that whales are derived from or are closely related to the [[mesonychid]]s. Many morphologists{{Who|date=March 2010}} and paleontologists support the notion of a clade called Cetartiodactyla that unites Cetacea with Artiodactyla. Many{{Who|date=March 2010}} are not, however, in support of the hypothesis that Cetacea evolved from within the Artiodactyla. Under this definition, Artiodactyla remains a valid clade since artiodactyls evolved from a common ancestor separate from whales. Cetartiodactyla would represent a [[grandorder]] or [[superorder]] uniting the two orders.

The vast majority of phylogenetic analyses based on morphological characters have not uncovered a whale/hippo clade, but show Cetacea and Artiodactyla as distinct from one another.{{Citation needed|date=January 2009}} Features of the bones of the [[talus bone|astragalus]] in the ankle region are cited as particular evidence for a monophyletic Artiodactyla. In any case, an origin of the Cetacea from within the [[Ungulata]] was proposed as early as 1900 by [[Frank Evers Beddard]] in ''A book of whales''. But, Beddard found the anatomical and fossil record at that time insufficient to rule out other possibilities, such as the notion that whales are a [[basal (evolution)|basal]] lineage among placental mammals, or the popular theory relating them to terrestrial carnivores. Because Beddard himself was not fully convinced, his bold proposal was largely forgotten.

Hippo fossils have not been observed until the [[Miocene]] (23 to 5 Ma), but whale ancestors have been dated to the [[Eocene]] (56 to 34 Ma). The whale/hippo hypothesis imposes a gap of nearly 30 million years where no hippo ancestors are present. Certain [[anthracothere]]s have been proposed as hippo ancestors, but this concept has not garnered wide support among paleontologists.{{citation needed|date=May 2013}} However, the most recent hypothesis into the origins of hippopotamids suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other Artiodactyls around {{mya|60|million years ago}}.<ref name="ScienceNews">{{cite web | title = Scientists find missing link between the dolphin, whale and its closest relative, the hippo | date = 2005-01-25 | accessdate = 2007-06-18 | url = http://www.sciencenewsdaily.org/story-2806.html | work = Science News Daily}}{{dead link|date=August 2013}}</ref><ref name="DNA">{{Cite journal | url = http://mbe.oxfordjournals.org/cgi/content/abstract/14/5/537 | title = More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen | author = Gatesy, J. | journal = [[Molecular Biology and Evolution]] | volume = 14 | pages = 537–543 | pmid = 9159931 | issue = 5 | year = 1997 | doi=10.1093/oxfordjournals.molbev.a025790}}</ref> This hypothesized ancestral group likely split into two branches around {{mya|54|million years ago}}.<ref name="Genomes">{{Cite journal | title = Analyses of mitochondrial genomes strongly support a hippopotamus-whale clade | volume = 265 | issue = 1412 | year = 1998 | pages = 2251–5 | journal = [[Proceedings of the Royal Society]] | author = Ursing,B.M. |author2=U. Arnason | doi = 10.1098/rspb.1998.0567 | pmid = 9881471 | pmc = 1689531}}</ref> One branch would [[Evolution of cetaceans|evolve into cetaceans]], possibly beginning with the proto-whale ''[[Pakicetus]]'' from {{mya|52|million years ago}} with other early whale ancestors collectively known as [[Archaeoceti]], which eventually underwent [[aquatic adaptation]] into the completely aquatic [[cetacea]]ns.<ref name="Cetartiodactyla">{{cite journal |last=Boisserie |first=Jean-Renaud |coauthors= Fabrice Lihoreau and Michel Brunet |date=February 2005|title= The position of Hippopotamidae within Cetartiodactyla|journal= [[Proceedings of the National Academy of Sciences]] |volume= 102 |issue= 5|pages= 1537–1541|doi= 10.1073/pnas.0409518102|pmid= 15677331 |pmc=547867}}</ref> Thus, Cetartiodactyla is supported as a monophyletic group.

==Chromosome number==

The ancestral cetartiodactyl karyotype is 2n = 48.<ref name="Kulemzina2011">Kulemzina AI, Yang F, Trifonov VA, Ryder OA, Ferguson-Smith MA, Graphodatsky AS (2011) Chromosome painting in Tragulidae facilitates the reconstruction of Ruminantia ancestral karyotype. Chromosome Res.</ref>

==Cladograms==

{{Laurasiatheria Cladogram}}
{{Cetartiodactyla Cladogram}}

==See also==
{{Wikispecies|Cetartiodactyla}}
* [[Evolution of cetaceans]]

==References==
{{reflist|35em}}
{{-}}
{{refbegin|35em}}
*{{cite journal | doi = 10.1016/j.ympev.2008.05.046 | last1 = Agnarsson | first1 = I. | last2 = May-Collado | first2 = L. | year = 2008 | title = The phylogeny of Cetartiodactyla: the importance of dense taxon sampling, missing data, and the remarkable promise of Cytochrome b to provide reliable species-level phylogenies | url = | journal = Molecular Phylogenetics and Evolution | volume = 48 | issue = 3| pages = 964–985 | pmid = 18590827 }}
*{{cite journal | doi = 10.1073/pnas.0409518102 | last1 = Boissere | first1 = J.-R. | last2 = Lihoreau | first2 = F. | last3 = Brunet | first3 = M. | year = 2005 | title = The position of Hippopotamidae within Cetartiodactyla | url = | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 102 | issue = 5| pages = 1537–1541 | pmid = 15677331 | pmc = 547867 }}
*{{cite journal | last1 = Gatesy | first1 = J. | year = 1997 | title = More support for a Cetacea / Hippopotamidae clade: The blood clotting protein gene g-fibrinogen | url = | journal = Molecular Biology and Evolution | volume = 14 | issue = 5| pages = 537–543 | pmid = 9159931 | doi=10.1093/oxfordjournals.molbev.a025790}}
*{{cite journal | last1 = Gatesy | first1 = J. | last2 = Hayashi | first2 = C. | last3 = Cronin | first3 = M. | last4 = Arctander | first4 = P. | year = 1996 | title = Evidence from milk casein genes that cetaceans are close relatives of hippopotamid artiodactyls | url = | journal = Molecular Biology and Evolution | volume = 13 | issue = 7| pages = 954–963 | pmid = 8752004 | doi = 10.1093/oxfordjournals.molbev.a025663 }}
*{{cite journal | doi = 10.1080/10635150290102311 | last1 = Gatesy | first1 = J. | last2 = Mathee | first2 = C. | last3 = DeSalle | first3 = R. | last4 = Hayashi | first4 = C. | year = 2002 | title = Resolution of a supertree/supermatrix paradox | url = | journal = Systematic Biology | volume = 51 | issue = 4| pages = 652–664 | pmid = 12228007 }}
*{{cite journal | doi = 10.1080/106351599260409 | last1 = Gatesy | first1 = J. | last2 = Milinkovitch | first2 = M. | last3 = Waddell | first3 = V. | last4 = Stanhope | first4 = M. | year = 1999 | title = Stability of cladistic relationships between Cetacea and higher-level artiodactyl taxa | url = | journal = Systematic Biology | volume = 48 | issue = 1| pages = 6–20 | pmid = 12078645 }}
*{{cite journal | last1 = Graur | first1 = D. | last2 = Higgins | first2 = D. | author-separator =, | author-name-separator= | year = 1994 | title = Molecular evidence for the inclusion of cetaceans within the order Artiodactyla | url = | journal = Molecular Biology and Evolution | volume = 11 | issue = 3| pages = 357–364 | pmid = 8015431 }}
*{{cite journal | doi = 10.1016/j.ympev.2005.09.019 | last1 = May-Collado | first1 = L. | last2 = Agnarsson | first2 = I. | year = 2006 | title = Cytochrome b and Bayesian inference of whale phylogeny | url = | journal = Molecular Phylogenetics and Evolution | volume = 38 | issue = 2| pages = 344–354 | pmid = 16325433 }}
*{{cite journal | doi = 10.1038/41650 | last1 = Milinkovitch | first1 = M. C. | last2 = Thewissen | first2 = J. G. M. | author-separator =, | author-name-separator= | year = 1997 | title = Even-toed fingerprints on whale ancestry | url = | journal = Nature | volume = 388 | issue = 6643| pages = 622–624 | pmid = 9262391 }}
*{{cite journal | last1 = Montgelard | first1 = C. | last2 = Catzeflis | first2 = F. | last3 = Douzery | first3 = E. | year = 1997 | title = Phylogenetic relationships among cetartiodactyls and cetaceans as deduced from the comparison of cytochrome b and 12S RNA mitochondrial sequences | url = | journal = Molecular Biology and Evolution | volume = 14 | issue = 5| pages = 550–559 | pmid = 9159933 | doi = 10.1093/oxfordjournals.molbev.a025792 }}
*{{cite journal | last1 = Naylor | first1 = G. J. P. | last2 = Adams | first2 = D. C. | author-separator =, | author-name-separator= | year = 2001 | title = Are the fossil data really at odds with the molecular data? Morphological evidence for Cetartiodactyla phylogeny reexamined | url = | journal = Systematic Biology | volume = 50 | issue = 3| pages = 444–453 | pmid = 12116586 | doi = 10.1080/106351501300318030 }}
*{{cite journal | doi = 10.1080/106351599260102 | last1 = O'Leary | first1 = M. A. | last2 = Geisler | first2 = J. H. | author-separator =, | author-name-separator= | year = 1999 | title = The position of Cetacea within Mammalia: phylogenetic analysis of morphological data from extinct and extant taxa | url = | journal = Systematic Biology | volume = 48 | issue = 3| pages = 455–490 | pmid = 12066291 }}
*{{cite journal | doi = 10.1073/pnas.96.18.10261 | last1 = Nikaido | first1 = M | last2 = Rooney | first2 = AP | last3 = Okada | first3 = N | author-separator =, | author-name-separator= | year = 1999 | title = Phylogenetic relationships among cetartiodactyls based on insertions of short and long interpersed elements: Hippopotamuses are the closest extant relatives of whales | url = | journal = Proc Natl Acad Sci U S A | volume = 96 | issue = 18| pages = 10261–10266 | pmid = 10468596 | pmc = 17876 }}
*{{cite journal | doi = 10.1080/106351500750049851 | last1 = Shedlock | first1 = A. M. | last2 = Milinkovitch | first2 = M. C. | last3 = Okada | first3 = N. | year = 2000 | title = SINE evolution, missing data, and the origin of whales | url = | journal = Systematic Biology | volume = 49 | issue = 4| pages = 808–816 }}
*{{cite doi |10.1038/41759 }}
*{{cite journal | doi = 10.1038/35095005 | last1 = Thewissen | first1 = J. G. | last2 = Williams | first2 = E. M. | last3 = Roe | first3 = L. J. | last4 = Hussain | first4 = S. T. | year = 2001| title = Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls | url = | journal = Nature | volume = 413 | issue = 6853| pages = 277–281 | pmid = 11565023 }}
{{refend}}


[[Category:Ungulates]]
[[Category:Ungulates]]
[[Category:Taxa described in 1997]]

[[Category:Mammal orders]]
[[ca:Artiodàctil#Taxonomia]]

Latest revision as of 00:46, 13 December 2023

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