Editing Archelon (section)

{{Short description|Cretaceous marine turtle and the largest turtle ever discovered}}
{{Distinguish|ARCHELON, the Sea Turtle Protection Society of Greece}}
{{Italic title}}
{{Good article}}
{{Use American English|date=September 2020}}
{{Use mdy dates|date=September 2020}}
{{Speciesbox
| fossil_range = [[Campanian]], {{fossil range|80.21|74.21}}<ref name=GeologicTime>{{citation|last1=Ogg|first1=J. G.|last2=Hinnov|first2=L. A.|chapter=Cretaceous|year=2012|pages=793–853|editor-last1=Gradstein|editor-first1=F. M.|editor-last2=Ogg|editor-first2=J. G.|editor-last3=Schmitz|editor-first3=M. D.|editor-last4=Ogg|editor-first4=G. M.|title=The Geologic Time Scale|publisher=Elsevier|location=Oxford|doi=10.1016/B978-0-444-59425-9.00027-5|isbn=978-0-444-59425-9|s2cid=127523816}}</ref><ref name=MartinandStewart>{{cite journal|author1=Martin, L. D.|author2= Stewart, J. D.|title=An ichthyornithiform bird from the Campanian of Canada|year=1981|journal=Canadian Journal of Earth Sciences|volume=19|issue=2|pages=324–327|doi=10.1139/e82-024}}</ref><ref name=hoganson>{{cite journal|first1=J. W.|last1=Hoganson|first2=B.|last2=Woodward|year=2004|title=Skeleton of the Rare Giant Sea Turtle, ''Archelon'', Recovered from the Cretaceous DeGrey Member of the Pierre Shale near Cooperstown, Griggs County, North Dakota|journal=North Dakota Geological Society Newsletter|volume=32|issue=1|pages=1–4|url=https://www.dmr.nd.gov/ndfossil/education/pdf/Archelon.pdf|access-date=December 23, 2018|archive-date=October 18, 2020|archive-url=https://web.archive.org/web/20201018221547/https://www.dmr.nd.gov/ndfossil/education/pdf/Archelon.pdf|url-status=dead}}</ref><ref name=DeGrey>{{cite journal|first1=J. E.|last1=Fox|title=Mollusks from the late Campanian upper DeGrey Formation of the Pierre Shale Group, Missouri River Valley, central South Dakota|journal=Geological Society of America Special Papers|year=2007|volume=427|pages=85–98|doi=10.1130/2007.2427(06)|isbn=978-0-8137-2427-0 |s2cid=133174376|url={{google books|plainurl=yes|id=RVqA3-Ay1wkC|page=85}}}}</ref>
| image = Big fossil turtle.jpg
| image_caption = Mounted cast at the [[University of Manitoba]]
| image_alt = A suspended display
| parent_authority = [[George Reber Wieland|Wieland]], 1896
| genus = Archelon
| species = ischyros
| authority = [[George Reber Wieland|Wieland]], 1896
| display_parents = 2
}}

'''''Archelon''''' is an extinct marine turtle from the [[Late Cretaceous]], and is  the largest turtle ever to have been documented, with the biggest specimen measuring {{cvt|4.6|m|ft}} from head to tail and {{cvt|2.2|-|3.2|MT|ST}} in body mass. It is known only from the [[Pierre Shale]] and has one species, '''''A. ischyros'''''. In the past, the genus also contained ''A. marshii'' and ''A. copei'', though these have been reassigned to ''[[Protostega]]'' and ''[[Kansastega]]'', respectively. The genus was named in 1896 by American paleontologist George Reber Wieland based on a skeleton from South Dakota, who placed it into the extinct [[family (biology)|family]] [[Protostegidae]]. The [[leatherback sea turtle]] (''Dermochelys coriacea'') was once thought to be its closest living relative, but now, Protostegidae is thought to be a completely separate lineage from any living [[sea turtle]].

''Archelon'' had a leathery [[carapace]] instead of the hard shell seen in most sea turtles. The carapace may have featured a row of small ridges, each peaking at {{cvt|2.5|or|5|cm|in|sigfig=1}} in height. It had an especially hooked beak and its jaws were adept at crushing, so it probably ate hard-shelled [[crustaceans]], [[mollusks]], and possibly even [[sponges]], while slowly moving over the seafloor. It also potentially consumed other animals, whilst swimming closer to the surface, like [[jellyfish]], [[squid]], or [[nautiloids]]. However, its beak may have been better-adapted for [[shearing (physics)|shearing]] flesh, with fish being another possible prey choice. With its large and strong foreflippers, ''Archelon'' was likely able to produce powerful strokes necessary for open-ocean travel and, if need be, escape from fellow marine predators. It inhabited the northern [[Western Interior Seaway]], a mild to cool temperate area, dominated by [[plesiosaur]]s, [[hesperornithiform]] seabirds, and [[mosasaur]]s. It may have gone extinct due to the shrinking of the seaway, increased infant mortality rates (in the sea), higher instances of egg and hatchling predation (on land), and a rapidly cooling climate.