Editing Cenozoic (section)

===Paleogene===
The [[Paleogene]] spans from the extinction of non-avian dinosaurs, 66 million years ago, to the dawn of the Neogene, 23.03&nbsp;million years ago. It features three [[epoch (geology)|epoch]]s: the [[Paleocene]], [[Eocene]] and [[Oligocene]].  [[File:Basilosaurus.jpg|thumb|left|''[[Basilosaurus]]'']]

The [[Paleocene Epoch]] lasted from 66 million to 56&nbsp;million years ago. Modern placental mammals originated during this time.<ref name="O'Leary-2013">{{cite journal |last1=O'Leary |first1=Maureen A. |last2=Bloch |first2=Jonathan I. |last3=Flynn |first3=John J. |last4=Gaudin |first4=Timothy J. |last5=Giallombardo |first5=Andres |last6=Giannini |first6=Norberto P. |last7=Goldberg |first7=Suzann L. |last8=Kraatz |first8=Brian P. |last9=Luo |first9=Zhe-Xi |last10=Meng |first10=Jin |last11=Ni |first11=Michael J. |last12=Novacek |first12=Fernando A. |last13=Perini |first13=Zachary S. |last14=Randall |first14=Guillermo |last15=Rougier |first15=Eric J. |last16=Sargis |first16=Mary T. |last17=Silcox |first17=Nancy b. |last18=Simmons |first18=Micelle |last19=Spaulding |first19=Paul M. |last20=Velazco |first20=Marcelo |last21=Weksler |first21=John r. |last22=Wible |first22=Andrea L. |title=The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals |date=8 February 2013 |journal=[[Science (journal)|Science]] |volume=339 |pages=662–667 |doi=10.1126/science.1229237 |pmid=23393258 |issue=6120 |last23=Cirranello |first23=A. L. |bibcode=2013Sci...339..662O |hdl=11336/7302 |s2cid=206544776 |hdl-access=free }}</ref> The devastation of the [[K–Pg extinction event]] included the extinction of large [[Herbivore|herbivores]], which permitted the spread of dense but usually species-poor forests.<ref name="Williams-2009">{{cite journal|first1=C. J.|last1=Williams|first2=B. A.|last2=LePage|first3=A. H.|last3=Johnson|first4=D. R.|last4=Vann|year=2009|title=Structure, Biomass, and Productivity of a Late Paleocene Arctic Forest|journal= Proceedings of the Academy of Natural Sciences of Philadelphia|volume=158|issue=1|pages=107–127|doi=10.1635/053.158.0106|s2cid=130110536}}</ref><ref>{{cite journal |last1=Johnson |first1=Kirk R. |last2=Ellis |first2=Beth |title=A Tropical Rainforest in Colorado 1.4 Million Years After the Cretaceous-Tertiary Boundary |journal=Science |date=28 June 2002 |volume=296 |issue=5577 |pages=2379–2383 |doi=10.1126/science.1072102|pmid=12089439 |bibcode=2002Sci...296.2379J |s2cid=11207255 }}</ref> The Early Paleocene saw the recovery of Earth. The continents began to take their modern shape, but all the continents and the subcontinent of India were separated from each other. [[Afro-Eurasia]] was separated by the [[Tethys Sea]], and the Americas were separated by the strait of Panama, as the [[Isthmus of Panama|isthmus]] had not yet formed. This epoch featured a general warming trend, with jungles eventually reaching the poles. The oceans were dominated by sharks<ref>{{Citation|last=Royal Tyrrell Museum|title=Lamniform sharks: 110 million years of ocean supremacy|date=28 March 2012|url=https://www.youtube.com/watch?v=e4p9EWuVxYQ| archive-url=https://web.archive.org/web/20130807114000/http://www.youtube.com/watch?v=e4p9EWuVxYQ&gl=US&hl=en| archive-date=7 August 2013 | url-status=dead|access-date=12 July 2017}}</ref> as the large reptiles that had once predominated were extinct. Archaic mammals filled the world such as [[creodonts]] (extinct carnivores, unrelated to existing [[Carnivora]]).

The [[Eocene Epoch]] ranged from 56 million years to 33.9&nbsp;million years ago. In the Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. Among them were early primates, whales and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as [[Paracrax]]. Carbon dioxide levels were approximately 1,400 [[Parts per million|ppm]].<ref>{{cite journal |last1=Anagnostou |first1=Eleni |last2=John |first2=Eleanor H. |last3=Edgar |first3=Kirsty M. |last4=Foster |first4=Gavin L. |last5=Ridgwell |first5=Andy |last6=Inglis |first6=Gordon N. |last7=Pancost |first7=Richard D. |last8=Lunt |first8=Daniel J. |last9=Pearson |first9=Paul N. |date=25 April 2016 |title=Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate |url=https://www.nature.com/articles/nature17423?error=cookies_not_supported&code=0e2a9a94-0fff-4718-853e-0a344e2fa5d0 |journal=[[Nature (journal)|Nature]] |volume=533 |issue=7603 |pages=380–384 |doi=10.1038/nature17423 |pmid=27111509 |s2cid=205248384 |access-date=19 January 2023|hdl=1983/799fc7ff-ff17-41b7-8dcc-cae1b66c5734 |hdl-access=free }}</ref> The temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In the Mid-Eocene, the [[Antarctic Circumpolar Current]] between Australia and Antarctica formed. This disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become almost fully aquatic. Mammals like ''[[Andrewsarchus]]'' were at the top of the food-chain. The Late Eocene saw the rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of [[grasses]].<ref>{{cite web|url=http://www.ucmp.berkeley.edu/tertiary/eocene.php|title=Eocene Climate|author=University of California|work=University of California}}</ref><ref>{{cite web|url=http://science.nationalgeographic.com/science/prehistoric-world/paleogene/|archive-url=https://web.archive.org/web/20100508003008/http://science.nationalgeographic.com/science/prehistoric-world/paleogene/|url-status=dead|archive-date=8 May 2010|title=Eocene|author=National Geographic Society|work=National Geographic|date=24 January 2017}}</ref> The end of the Eocene was marked by the [[Eocene–Oligocene extinction event]],<ref>{{cite journal |last1=Retallack |first1=Gregory J. |last2=Orr |first2=William N. |last3=Prothero |first3=Donald Ross |last4=Duncan |first4=Robert A. |last5=Kester |first5=Paul R. |last6=Ambers |first6=Clifford P. |date=1 July 2004 |title=Eocene–Oligocene extinction and paleoclimatic change near Eugene, Oregon |url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/116/7-8/817/2099/Eocene-Oligocene-extinction-and-paleoclimatic |journal=[[Geological Society of America Bulletin]] |volume=116 |issue=7–8 |pages=817–839 |doi=10.1130/B25281.1 |bibcode=2004GSAB..116..817R |access-date=16 April 2023}}</ref><ref>{{cite journal |last1=Prothero |first1=Donald Ross |title=The Late Eocene-Oligocene Extinctions |date=May 1994 |url=https://www.annualreviews.org/doi/abs/10.1146/annurev.ea.22.050194.001045?journalCode=earth |journal=[[Annual Review of Earth and Planetary Sciences]] |volume=22 |pages=145–165 |doi=10.1146/annurev.ea.22.050194.001045 |bibcode=1994AREPS..22..145P |access-date=16 April 2023}}</ref><ref name="Ivany-2000">{{Cite journal |last1=Ivany |first1=Linda C. |last2=Patterson |first2=William P. |last3=Lohmann |first3=Kyger C. |title=Cooler winters as a possible cause of mass extinctions at the Eocene/Oligocene boundary |journal=[[Nature (journal)|Nature]] |volume=407 |issue=6806 |pages=887–890 |doi=10.1038/35038044|pmid=11057663|year=2000|hdl=2027.42/62707 |url=https://deepblue.lib.umich.edu/bitstream/2027.42/62707/1/407887a0.pdf |bibcode=2000Natur.407..887I |s2cid=4408282 |hdl-access=free}}</ref> the European face of which is known as the [[Grande Coupure]].<ref>{{cite journal |last1=Zhang |first1=R. |last2=Kravchinsky |first2=V.A. |last3=Yue |first3=L. |date=21 May 2012 |title=Link between Global Cooling and Mammalian Transformation across the Eocene–Oligocene Boundary in the Continental Interior of Asia |url=https://link.springer.com/article/10.1007/s00531-012-0776-1 |journal=[[International Journal of Earth Sciences]] |volume=101 |issue=8 |pages=2193–2200 |doi=10.1007/s00531-012-0776-1 |bibcode=2012IJEaS.101.2193Z |s2cid=55409146 |access-date=4 August 2023 }}</ref><ref>{{Cite journal |pmid=10588762 |date=December 1999 |author1=Köhler, M |author2=Moyà-Solà, S |title=A finding of Oligocene primates on the European continent |url=https://www.researchgate.net/publication/12712095 |volume=96 |issue=25 |pages=14664–7 |issn=0027-8424 |pmc=24493 |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |doi=10.1073/pnas.96.25.14664 |bibcode=1999PNAS...9614664K |doi-access=free |access-date=28 July 2023}}</ref>

The [[Oligocene Epoch]] spans from 33.9&nbsp;million to 23.03&nbsp;million years ago. The Oligocene featured the expansion of grasslands which had led to many new species to evolve, including the first elephants, cats, dogs, marsupials and many other species still prevalent today. Many other species of plants evolved in this period too. A cooling period featuring seasonal rains was still in effect. Mammals still continued to grow larger and larger.<ref>{{cite web|url=http://www.ucmp.berkeley.edu/tertiary/oligocene.php|title=Oligocene|author=University of California|work=University of California}}</ref>