Editing Apomorphy and synapomorphy (section)

{{short description|Two concepts on heritable traits}}
[[Image:synapomorphy.jpg|thumb|279px|[[Phylogenies]] showing the terminology used to describe different patterns of ancestral and derived character or [[Phenotypic trait|trait]] states.<ref name="PageHolmes2009">{{cite book|author1=Roderick D.M. Page|author2=Edward C. Holmes|title=Molecular Evolution: A Phylogenetic Approach|url=https://books.google.com/books?id=p2lWhjuK8m8C|date=14 July 2009|publisher=John Wiley & Sons|isbn=978-1-4443-1336-9}}</ref>]]

In [[phylogenetics]], an '''apomorphy''' (or '''derived trait''') is a novel [[Phenotypic trait|character]] or character state that has [[evolution|evolved]] from its ancestral form (or [[Plesiomorphy and symplesiomorphy|plesiomorphy]]).<ref name="Futuyma2017b">{{cite book |last1 = Futuyma | first1 = Douglas J. | last2 = Kirkpatrick | first2 = Mark | date = 2017| pages=27–53 | chapter = Tree of life | title = Evolution | edition = 4th | publisher = Sinauer Associates | location = Sunderland, Mass.}}</ref><ref name="Futuyma2017p">{{cite book |last1 = Futuyma | first1 = Douglas J. | last2 = Kirkpatrick | first2 = Mark | date = 2017| pages=401–429 | chapter = Phylogeny: The unity and diversity of life | title = Evolution | edition = 4th | publisher = Sinauer Associates | location = Sunderland, Mass.}}</ref><ref name = "berkeleybiology">{{cite web | title = Reconstructing trees: Cladistics | website = Understanding Evolution | date = 5 May 2021 | url = https://evolution.berkeley.edu/evolibrary/article/phylogenetics_05 | publisher = University of California Museum of Paleontology | access-date = 16 October 2021 }}</ref> A '''synapomorphy''' is an apomorphy shared by two or more [[taxon|taxa]] and is therefore [[Hypothesis#Scientific hypothesis|hypothesized]] to have evolved in their [[most recent common ancestor]].<ref name="PageHolmes2009"/><ref name = "kitchingetal2001"> {{cite encyclopedia | last1 = Kitching | first1 = Ian J. | last2 = Forey | first2 = Peter L. | last3 = Williams | first3 = David M. | editor-last = Levin | editor-first = Simon A. | title = Cladistics | encyclopedia = Encyclopedia of Biodiversity | year = 2001 | edition = 2nd | pages = 33–45 | publisher = Elsevier | doi = 10.1016/B978-0-12-384719-5.00022-8 | isbn = 9780123847201 | access-date = 29 August 2021 | url = https://www.sciencedirect.com/science/article/pii/B9780123847195000228| url-access = subscription }})</ref><ref name="Futuyma2017p">{{cite book |last1 = Futuyma | first1 = Douglas J. | last2 = Kirkpatrick | first2 = Mark | date = 2017| pages=401–429 | chapter = Phylogeny: The unity and diversity of life | title = Evolution | edition = 4th | publisher = Sinauer Associates | location = Sunderland, Mass.}}</ref><ref name="hillisetal2014p">{{cite book | last1 = Hillis | first1 = David M. | last2 = Sadava | first2 = David | last3 = Hill | first3 = Richard W. | last4= Price | first4 = Mary V. | chapter = Reconstructing and using phylogenies | title = Principles of Life | publisher = Sinauer Associates | edition = 2nd | date = 2014 | location = Sunderland, Mass. | pages = 325–342 | isbn = 978-1464175121}}</ref><ref>{{cite book | first1 = Philip J. | last1 = Currie | first2 = Kevin | last2 = Padia | name-list-style = vanc | title = Encyclopedia of Dinosaurs | url = https://books.google.com/books?id=7t9M5TsmjOUC&pg=PA543 | page = 543 | isbn = 978-0-08-049474-6 | publisher = Elsevier | date = 1997 }}</ref><ref>{{cite book|title=Concise Encyclopedia Biology |url=https://archive.org/details/conciseencyclope00scot |url-access=registration |date=1996 |publisher=Walter de Gruyter |location=Tubingen, DEU |page=[https://archive.org/details/conciseencyclope00scot/page/366 366] |isbn=9783110106619 }}</ref><ref name=":0">{{cite book |last1=Barton |first1=Nicholas |last2=Briggs |first2=Derek |last3=Eisen |first3=Jonathan |last4=Goldstein |first4=David| last5=Patel |first5=Nipam | name-list-style = vanc |title=Evolution |date=2007 |publisher=Cold Spring Harbor Laboratory Press |chapter-url=http://www.evolution-textbook.org/content/free/contents/ch27.html |chapter=Phylogenetic Reconstruction}}</ref> In [[cladistics]], synapomorphy implies [[Homology (biology)|homology]].<ref name = "kitchingetal2001"/>

Examples of apomorphy are the presence of [[Terrestrial locomotion#Posture|erect]] [[gait]], [[fur]], [[Evolution of mammalian auditory ossicles|the evolution of three  middle ear bones]], and [[mammary gland]]s in [[mammal]]s but not in other [[vertebrate]] [[animal]]s such as [[amphibian]]s or [[reptile]]s, which have retained their ancestral traits of a [[Terrestrial locomotion#Posture|sprawling]] gait and lack of fur.<ref name = "baum2008">{{cite journal | last1 = Baum | first1 = David | year = 2008 | title = Trait Evolution on a Phylogenetic Tree: Relatedness, Similarity, and the Myth of Evolutionary Advancement | journal = Nature Education | url = https://www.nature.com/scitable/topicpage/trait-evolution-on-a-phylogenetic-tree-relatedness-41936/ | volume = 1 | issue = 1 | page = 191 }}</ref> Thus, these derived traits are also synapomorphies of mammals in general as they are not shared by other vertebrate animals.<ref name = "baum2008"/>