Transitional fossil: Difference between revisions

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{{short description|Fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group}}

{{redirect|Transitional forms|the hardcore punk music album|Sharptooth}}

{{Use dmy dates|date=OctoberSeptember 20122020}}

{{short description|Fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group}}

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{{Paleontology|cTopic=Fossil record}}

A '''transitional fossil''' is any [[fossil]]ized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.<ref name="Freeman">{{harvnb|Freeman|Herron|2004|p=816}}</ref> This is especially important where the descendant group is sharply differentiated by [[gross anatomy]] and mode of living from the ancestral group. These fossils serve as a reminder that taxonomic divisions are [[human]] constructs that have been imposed in hindsight on a continuum of variation. Because of the incompleteness of the fossil record, there is usually no way to know exactly how close a transitional fossil is to the point of divergence. Therefore, it cannot be assumed that transitional fossils are direct ancestors of more recent groups, though they are frequently used as models for such ancestors.<ref name=Prothero/>

In 1859, when [[Charles Darwin]]'s ''[[On the Origin of Species]]'' was first published, the fossil record was poorly known. Darwin described the perceived lack of transitional fossils as, "... the most obvious and gravest objection which can be urged against my theory," but explained it by relating it to the extreme imperfection of the geological record.<ref>{{harvnb|Darwin|1859|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=297 279–280]}}</ref> He noted the limited collections available at that time, but described the available information as showing patterns that followed from his theory of [[evolution|descent with modification]] through [[natural selection]].<ref>{{harvnb|Darwin|1859|pp=[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F373&pageseq=359 341–343]}}</ref> Indeed, ''[[Archaeopteryx]]'' was discovered just two years later, in 1861, and represents a classic transitional form between earlier, non-avian [[dinosaur]]s and [[bird]]s. [[List of transitional fossils|Many more transitional fossils]] have been discovered since then, and there is now abundant evidence of how all [[class (biology)|classes]] of [[vertebrate]]s are related, including many transitional fossils.<ref name="NS2645">{{cite journal |last=Prothero |first=Donald R. |authorlink=Donald Prothero |date=1 March 2008 |title=Evolution: What missing link? |url=https://www.newscientist.com/article/mg19726451.700-evolution-what-missing-link.html?full=true |journal=[[New Scientist]] |issue=2645 |pages=35–41 |issn=0262-4079 |accessdate=2015-05-13 |doi=10.1016/s0262-4079(08)60548-5 |volume=197}}</ref> Specific examples of class-level transitions are: [[Evolution of tetrapods|tetrapod]]s and [[Evolution of fish|fish]], [[Origin of birds|birds and dinosaurs]], and [[Evolution of mammals|mammals and "mammal-like reptiles"]].

The term "missing link" has been used extensively in popular writings on [[human evolution]] to refer to a perceived gap in the [[Hominidae|hominid]] evolutionary record. It is most commonly used to refer to any new transitional fossil finds. Scientists, however, do not use the term, as it refers to a pre-evolutionary view of nature.

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* {{cite book |last1=Eldredge |first1=Niles |authorlink1=Niles Eldredge |last2=Gould |first2=Stephen Jay |authorlink2=Stephen Jay Gould |year=1972 |chapter=Punctuated equilibria: an alternative to phyletic gradualism |editor1-last=Schopf |editor1-first=Thomas J. M. |title=Models in Paleobiology |___location=San Francisco, CA |publisher=Freeman, Cooper |isbn=978-0-87735-325-6 |lccn=72078387 |oclc=572084 |ref=harv}}

* {{cite book |last1=Freeman |first1=Scott |last2=Herron |first2=Jon C. |year=2004 |title=Evolutionary Analysis |edition=3rd |___location=Upper Saddle River, NJ |publisher=[[Pearson Education]] |isbn=978-0-13-101859-4 |lccn=2003054833 |oclc=52386174 |ref=harv |url=https://archive.org/details/prenticehallguid00meli }}

* {{cite book |last1=Gingerich |first1=Philip D. |authorlink1=Philip D. Gingerich |last2=Russell |first2=Donald E. |year=1981 |title=Pakicetus inachus, a New Archaeocete (Mammalia, Cetacea) From the Early-Middle Eocene Kuldana Formation of Kohat (Pakistan) |url=http://deepblue.lib.umich.edu/bitstream/handle/2027.42/48501/ID352.pdf?sequence=2&isAllowed=y |format=PDF |type=Research report |series=Contributions from the Museum of Paleontology |volume=25 |issue=11 |___location=Ann Arbor, MI |publisher=[[University of Michigan Museum of Natural History|Museum of Paleontology, University of Michigan]] |pages=235–246 |issn=0097-3556 |lccn=82621252 |oclc=8263404 |ref=harv}}

* {{cite book |last=Gould |first=Stephen Jay |authorlink=Stephen Jay Gould |year=1980 |title=The Panda's Thumb: More Reflections in Natural History |edition=1st |___location=New York |publisher=[[W. W. Norton & Company]] |isbn=978-0-393-01380-1 |lccn=80015952 |oclc=6331415 |ref=harv|title-link=The Panda's Thumb (book) }}

* {{cite book |last=Haeckel |first=Ernst |authorlink=Ernst Haeckel |title=The Evolution of Man |year=2011 |origyear=Originally published 1912; London: [[Charles Watts (secularist)|Watts & Co.]] |volume=1 |others=Translated from the German by [[Joseph McCabe]] |edition=5th enlarged |___location=Hamburg, Germany |publisher=Tredition Classics |isbn=978-3-8424-6302-8 |oclc=830523724 |ref=harv}}

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* {{cite book |last=Prothero |first=Donald R. |authorlink=Donald Prothero |year=2007 |title=Evolution: What the Fossils Say and Why it Matters |others=Original illustrations by Carl Buell |___location=New York |publisher=[[Columbia University Press]] |isbn=978-0-231-13962-5 |lccn=2007028804 |oclc=154711166 |ref=harv |url=https://archive.org/details/evolutionwhatfos00prot_0 }}

* {{cite book |last=Reader |first=John |year=2011 |title=Missing Links: In Search of Human Origins |others=Foreword by Andrew Hill |edition=Enlarged and updated |___location=Oxford; New York |publisher=[[Oxford University Press]] |isbn=978-0-19-927685-1 |lccn=2011934689 |oclc=707267298 |ref=harv |url-access=registration |url=https://archive.org/details/missinglinksinse0000read }}

* {{cite book |last=Shubin |first=Neil |authorlink=Neil Shubin |year=2008 |title=Your Inner Fish: A Journey Intointo the 3.5-Billion-Year History of the Human Body |___location=New York |publisher=[[Pantheon Books]] |isbn=978-0-375-42447-2 |lccn=2007024699 |oclc=144598195 |ref=harv |url=https://archive.org/details/yourinnerfishjou00shub_0 }}

* {{cite book |last1=Swisher |first1=Carl C., III |last2=Curtis |first2=Garniss H. |authorlink2=Garniss Curtis |last3=Lewin |first3=Roger |authorlink3=Roger Lewin |year=2001 |origyear=Originally published 2000 |title=Java Man: How Two Geologists Changed Our Understanding of Human Evolution |___location=Chicago, IL |publisher=[[University of Chicago Press]] |isbn=978-0-226-78734-3 |lccn=2001037337 |oclc=48066180 |ref=harv}}

* {{cite book |last=Wellnhofer |first=Peter |authorlink=Peter Wellnhofer |year=2004 |chapter=The Plumage of ''Archaeopteryx'': Feathers of a Dinosaur? |editor1-last=Currie |editor1-first=Philip J. |editor1-link=Philip J. Currie |editor2-last=Koppelhus |editor2-first=Eva B. |editor3-last=Shugar |editor3-first=Martin A. |display-editors = 3 |editor4-last=Wright |editor4-first=Joanna L. |title=Feathered Dragons: Studies on the Transition from Dinosaurs to Birds |series=Life of the Past |___location=Bloomington, IN |publisher=[[Indiana University Press]] |isbn=978-0-253-34373-4 |lccn=2003019035 |oclc=52942941 |ref=harv}}

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* {{cite web |url=http://www.ucmp.berkeley.edu/diapsids/avians.html |title=Are Birds Really Dinosaurs? |last=Hutchinson |first=John R. |date=22 January 1998 |website=DinoBuzz |publisher=[[University of California Museum of Paleontology]] |___location=Berkeley, CA |accessdate=2015-05-19}}

{{Use dmy dates|date=October 2012}}

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