Transitional fossil: Difference between revisions

Revision as of 09:57, 1 October 2022

Revision as of 05:47, 4 October 2022

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[[File:Tiktaalik Chicago.JPG|thumb|left|''[[Tiktaalik|Tiktaalik roseae]]'' had [[Spiracle (vertebrates)|spiracle]]s (air holes) above the eyes.]]

[[File:Tiktaalik BW.jpg|thumb|250px|Life restoration of ''Tiktaalik roseae'']]

''Tiktaalik'' is a genus of extinct [[Sarcopterygii|sarcopterygian]] (lobe-finned fish) from the Late [[Devonian]] period, with many features akin to those of tetrapods (four-legged animals).<ref name="Nature">{{cite journal |last1=Daeschler |first1=Edward B. |author-link1=Ted Daeschler |last2=Shubin |first2=Neil H. |author-link2=Neil Shubin |last3=Jenkins | first3=Farish A., Jr. |author-link3=Farish Jenkins |date=6 April 2006 |title=A Devonian tetrapod-like fish and the evolution of the tetrapod body plan |journal=Nature |volume=440 |issue=7085 |pages=757–763 |bibcode=2006Natur.440..757D |doi=10.1038/nature04639 |issn=0028-0836 |pmid=16598249 |doi-access=free }}</ref> It is one of several lines of ancient sarcopterygians to develop adaptations to the oxygen-poor shallow water habitats of its time—adaptations that led to the evolution of tetrapods.<ref name="scientificamerican">{{cite journal |last=Clack |first=Jennifer A. |author-link=Jenny Clack |date=December 2005 |title=Getting a Leg Up on Land |journal=Scientific American |volume=293 |pages=100–107 |issue=6 |bibcode=2005SciAm.293f.100C |doi=10.1038/scientificamerican1205-100 |issn=0036-8733 |pmid=16323697 }}</ref> Well-preserved fossils were found in 2004 on [[Ellesmere Island]] in [[Nunavut]], Canada.<ref>{{cite journal |last=Easton |first=John |date=23 October 2008 |title=''Tiktaalik's'' internal anatomy explains evolutionary shift from water to land |url=http://chronicle.uchicago.edu/081023/tiktaalik.shtml |journal=University of Chicago Chronicle |issue=3 |volume=28 |issn=1095-1237 |access-date=2012-04-19 }}</ref>

''Tiktaalik'' lived approximately 375&nbsp;million years ago. [[Paleontology|Paleontologist]]s suggest that it is representative of the transition between non-tetrapod vertebrates such as ''[[Panderichthys]]'', known from fossils 380&nbsp;million years old, and early tetrapods such as ''[[Acanthostega]]'' and ''[[Ichthyostega]]'', known from fossils about 365&nbsp;million years old. Its mixture of primitive fish and derived tetrapod characteristics led one of its discoverers, [[Neil Shubin]], to characterize ''Tiktaalik'' as a "[[Tetrapodomorpha|fishapod]]."<ref>{{cite news |last=Wilford |first=John Noble |author-link=John Noble Wilford |date=5 April 2006 |title=Scientists Call Fish Fossil the 'Missing Link' |url=https://www.nytimes.com/2006/04/05/science/05cnd-fossil.html |newspaper=[[The New York Times]] |access-date=2015-05-17}}</ref><ref>{{harvnb|Shubin|2008}}</ref> Unlike many previous, more fish-like transitional fossils, the "fins" of ''Tiktaalik'' have basic wrist bones and simple rays reminiscent of fingers. They may have been [[weight-bearing]]. Like all modern tetrapods, it had rib bones, a mobile neck with a separate pectoral girdle, and lungs, though it had the gills, scales, and fins of a fish.<ref name="Nature" /> However in a 2008 paper by Boisvert at al. it is noted that ''Panderichthys'', due to its more derived distal portion, might be closer to tetrapods than ''Tiktaalik'', which might have independently developed similarities to tetrapods by convergent evolution.<ref>{{cite web|url=http://uu.diva-portal.org/smash/get/diva2:221262/FULLTEXT01 |title=Pectoral fin info |publisher=uu.diva-portal.org |date= |access-date=2021-05-09}}</ref>

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==Sources==

{{Refbegin}}

* {{cite book |last=Andrews | first=Henry N., Jr. |title=Studies in Paleobotany |year=1967 |orig-year=Originally published 1961 |edition=Reprint |others=Chapter on palynology by Charles J. Felix |___location=New York |publisher=[[John Wiley & Sons]] |lccn=61006768 |oclc=12877482 }}

* {{cite book |last=Benton |first=Michael J. |author-link=Michael Benton |year=1997 |edition=2nd |title=Vertebrate Palaeontology |___location=London |publisher=[[Chapman & Hall]] |isbn=978-0-412-73810-4 |oclc=37378512 |title-link=Vertebrate Palaeontology (Benton) }}

* {{cite book |last=Browne |first=Janet |author-link=Janet Browne |year=2003 |orig-year=Originally published 2002 |title=Charles Darwin: The Power of Place |volume=2 |___location=London |publisher=[[Jonathan Cape]] |isbn=978-0-7126-6837-8 |oclc=806284755 }}