| 词条 | Stem tetrapoda |
| 释义 |
The Stem Tetrapoda are a cladistically defined group, consisting of all animals more closely related to extant four-legged vertebrates than to their closest extant relatives (the lungfish), but excluding the crown group Tetrapoda. They are thus paraphyletic, though acceptable in phylogenetic nomenclature as the group is defined by strict reference to phylogeny rather than to traits as in traditional systematics. Sarcopterygian fish are considered to be stem tetrapods. Content of the group{{Main|Tetrapodomorpha|Labyrinthodontia}}Stem tetrapods are members of Tetrapodomorpha, the total group and clade that also includes their descendants, the crown tetrapods:[1] The stem Tetrapoda encompass three distinct grades successively closer to crown group Tetrapoda:[2]
Both Ichthyostegalia and Labyrinthodontia constitute paraphyletic evolutionary grades rather than clades, with amniotes and modern amphibians branching off at some point from the latter. The stem tetrapods may also include one or both of Temnospondyli and Lepospondyli, depending on author. This is due to the uncertain origin of the modern amphibians, whose position in the phylogenetic tree dictates what lineages go in the crown group Tetrapoda.[3][4] Neither is there for the moment a consensus of the phylogeny of stem tetrapods, nor how Tetrapoda itself should be defined (i.e. as a crown group, or as an apomorphy-based group, using the limb with digits),[5] making the actual content of the group uncertain.[6][7][8] References1. ^1 {{cite journal|last=Coates|first=M.I.|author2=Ruta, M.|author3=Friedman, M.|year=2008|title=Ever Since Owen: Changing Perspectives on the Early Evolution of Tetrapods|url=http://webh01.ua.ac.be/funmorph/raoul/fylsyst/Coates2008.pdf|journal=Annual Review of Ecology, Evolution, and Systematics|volume=39|pages=571–92|doi=10.1146/annurev.ecolsys.38.091206.095546|archive-url=https://web.archive.org/web/20131029194107/http://webh01.ua.ac.be/funmorph/raoul/fylsyst/Coates2008.pdf|archive-date=29 October 2013|via=}} 2. ^{{cite journal|last=Ahlberg|first=P. E.|author2=Johanson, Z.|year=1998|title=Osteolepiforms and the ancestry of tetrapods|url=http://www.biology.ualberta.ca/courses.hp/biol606/papers/Ahlberg+1998.pdf|journal=Nature|volume=395|issue=6704|pages=792–794|bibcode=1998Natur.395..792A|doi=10.1038/27421|archive-url=https://web.archive.org/web/20170329042924/http://www.biology.ualberta.ca:80/courses.hp/biol606/papers/Ahlberg+1998.pdf|archive-date=29 March 2017|via=}} 3. ^{{cite journal | last1 = Sigurdsen | first1 = T. | last2 = Green | first2 = D.M. |name-list-format=vanc | year = 2011 | title = The origin of modern amphibians: a re-evaluation | journal = Zoological Journal of the Linnean Society | pmid = | volume = 162 | issue = 2| pages = 457–469 | doi = 10.1111/j.1096-3642.2010.00683.x }} 4. ^{{cite journal | last1 = Marjanović | first1 = D | last2 = Laurin | first2 = M | year = 2013 | title = The origin(s) of extant amphibians: a review with emphasis on the "lepospondyl hypothesis" | url = | journal = Geodiversitas | volume = 35 | issue = | pages = 207–272 | doi = 10.5252/g2013n1a8 }} 5. ^{{cite journal | last1 = Laurin | first1 = M | last2 = Anderson | first2 = JS | year = 2004 | title = Meaning of the name Tetrapoda in the scientific literature: an exchange | url = | journal = Systematic Biology | volume = 53 | issue = 1| pages = 68–80 | doi = 10.1080/10635150490264716 | pmid=14965901}} 6. ^{{cite journal | last1 = Carroll | first1 = R.L. | authorlink = Robert L. Carroll | year = 2001 | title = The origin and early radiation of terrestrial vertebrates | url = http://www.usfca.edu/fac_staff/dever/tetropodevol.pdf | journal = Journal of Paleontology | volume = 75 | issue = 6 | pages = 1202–1213 | doi = 10.1666/0022-3360(2001)075<1202:toaero>2.0.co;2 | deadurl = yes | archiveurl = https://web.archive.org/web/20120930202110/http://www.usfca.edu/fac_staff/dever/tetropodevol.pdf | archivedate = 2012-09-30 | df = }} 7. ^Laurin, M. (1996): Phylogeny of Stegocephalians, from the Tree of Life Web Project 8. ^{{cite journal | last1 = Laurin | first1 = M | year = 1998 | title = The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I. Systematics, middle ear evolution, and jaw suspension | journal = Annales des Sciences Naturelles, Zoologie, Paris, 13e Série | volume = 19 | issue = | pages = 1–42 | doi=10.1016/S0003-4339(98)80132-9}} 2 : Tetrapod taxonomy|Paraphyletic groups |
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