Editing Mammal (section)

===Rise of the mammals===
[[File:Hyaenodon horridus, Niobrara County, Wyoming, USA, Late Oligocene - Royal Ontario Museum - DSC00114.JPG|thumb|left|''[[Hyaenodon]] horridus'' at the [[Royal Ontario Museum]]. The genus ''Hyaenodon'' was among the most successful mammals of the late [[Eocene]]-early [[Miocene]] epochs spanning for most of the [[Paleogene]] and some of the [[Neogene]] periods, undergoing many endemic radiations in North America, Europe, and Asia.<ref>{{cite journal|last1=Pfaff|first1=Cathrin|last2=Nagel|first2=Doris|last3=Gunnell|first3=Gregg|last4=Weber|first4=Gerhard W.|last5=Kriwet|first5=Jürgen|last6=Morlo|first6=Michael|last7=Bastl|first7=Katharina|year=2017|title=Palaeobiology of Hyaenodon exiguus (Hyaenodonta, Mammalia) based on morphometric analysis of the bony labyrinth|journal=Journal of Anatomy|volume=230|issue=2|pages=282–289|doi=10.1111/joa.12545|pmid=27666133 |pmc=5244453 }}</ref>]]
Therians took over the medium- to large-sized ecological niches in the [[Cenozoic]], after the [[Cretaceous–Paleogene extinction event]] approximately 66&nbsp;million years ago emptied ecological space once filled by non-avian dinosaurs and other groups of reptiles, as well as various other mammal groups,<ref name="SahneyBentonFerry2010LinksDiversityVertebrates">{{cite journal | vauthors = Sahney S, Benton MJ, Ferry PA | title = Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land | journal = Biology Letters | volume = 6 | issue = 4 | pages = 544–547 | date = August 2010 | pmid = 20106856 | pmc = 2936204 | doi = 10.1098/rsbl.2009.1024 }}</ref> and underwent an exponential increase in body size ([[megafauna#In terrestrial mammals|megafauna]]).<ref name="F.A.Smith">{{cite journal | vauthors = Smith FA, Boyer AG, Brown JH, Costa DP, Dayan T, Ernest SK, Evans AR, Fortelius M, Gittleman JL, Hamilton MJ, Harding LE, Lintulaakso K, Lyons SK, McCain C, Okie JG, Saarinen JJ, Sibly RM, Stephens PR, Theodor J, Uhen MD | display-authors = 6 | title = The evolution of maximum body size of terrestrial mammals | journal = Science | volume = 330 | issue = 6008 | pages = 1216–1219 | date = November 2010 | pmid = 21109666 | doi = 10.1126/science.1194830 | citeseerx = 10.1.1.383.8581 | bibcode = 2010Sci...330.1216S | s2cid = 17272200 }}</ref> The increase in mammalian diversity was not, however, solely because of expansion into large-bodied niches.<ref>{{Cite journal |last1=Benevento |first1=Gemma Louise |last2=Benson |first2=Roger B. J. |last3=Close |first3=Roger A. |last4=Butler |first4=Richard J. |date=16 June 2023 |title=Early Cenozoic increases in mammal diversity cannot be explained solely by expansion into larger body sizes |journal=[[Palaeontology (journal)|Palaeontology]] |language=en |volume=66 |issue=3 |page=12653 |doi=10.1111/pala.12653 |issn=0031-0239 |doi-access=free |bibcode=2023Palgy..6612653B }}</ref> Mammals diversified very quickly, displaying an exponential rise in diversity.<ref name="SahneyBentonFerry2010LinksDiversityVertebrates"/> For example, the earliest-known bat dates from about 50&nbsp;million years ago, only 16&nbsp;million years after the extinction of the non-avian dinosaurs.<ref>{{cite journal | vauthors = Simmons NB, Seymour KL, Habersetzer J, Gunnell GF | title = Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation | journal = Nature | volume = 451 | issue = 7180 | pages = 818–821 | date = February 2008 | pmid = 18270539 | doi = 10.1038/nature06549 | url = https://www.nature.com/articles/nature06549.epdf?referrer_access_token=vvnCZKFsJpI9PyHTMCW0AtRgN0jAjWel9jnR3ZoTv0OIjnS1VOVvLEmlM3pVKicSGILcK5-gC0KUTwfjLtGsWX-Jl3sk3aQbBWjeluiuMfZh8gMqZJ4qV9dfir4OcYHZFaqbm8GbWK-9JqFbcMEjN3G_-d7t8hJWLm5RDaih5vZhy47BSgJOQDuz8aRMBtHCvZEWV7affpdxsSefk_6x80U5fE1N1SjLKUHVdainKEM%3D&tracking_referrer=arstechnica.com | bibcode = 2008Natur.451..818S | hdl = 2027.42/62816 | s2cid = 4356708 | hdl-access = free | access-date = 25 January 2024 | archive-date = 25 January 2024 | archive-url = https://web.archive.org/web/20240125191352/https://www.nature.com/articles/nature06549.epdf?referrer_access_token=vvnCZKFsJpI9PyHTMCW0AtRgN0jAjWel9jnR3ZoTv0OIjnS1VOVvLEmlM3pVKicSGILcK5-gC0KUTwfjLtGsWX-Jl3sk3aQbBWjeluiuMfZh8gMqZJ4qV9dfir4OcYHZFaqbm8GbWK-9JqFbcMEjN3G_-d7t8hJWLm5RDaih5vZhy47BSgJOQDuz8aRMBtHCvZEWV7affpdxsSefk_6x80U5fE1N1SjLKUHVdainKEM%3D&tracking_referrer=arstechnica.com | url-status = live }}</ref>

Molecular phylogenetic studies initially suggested that most placental orders diverged about 100 to 85&nbsp;million years ago and that modern families appeared in the period from the late [[Eocene]] through the [[Miocene]].<ref name="Bininda2007">{{cite journal | vauthors = Bininda-Emonds OR, Cardillo M, Jones KE, MacPhee RD, Beck RM, Grenyer R, Price SA, Vos RA, Gittleman JL, Purvis A | display-authors = 6 | title = The delayed rise of present-day mammals | journal = Nature | volume = 446 | issue = 7135 | pages = 507–512 | date = March 2007 | pmid = 17392779 | doi = 10.1038/nature05634 | url = https://www.utheria.org/uploads/nature05634.pdf | bibcode = 2007Natur.446..507B | s2cid = 4314965 | access-date = 25 January 2024 | archive-date = 25 January 2024 | archive-url = https://web.archive.org/web/20240125191351/https://www.utheria.org/uploads/nature05634.pdf | url-status = live }}</ref> However, no placental fossils have been found from before the end of the Cretaceous.<ref name="Wible2007"/> The earliest undisputed fossils of placentals come from the early [[Paleocene]], after the extinction of the non-avian dinosaurs.<ref name="Wible2007">{{cite journal | vauthors = Wible JR, Rougier GW, Novacek MJ, Asher RJ | title = Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary | journal = Nature | volume = 447 | issue = 7147 | pages = 1003–1006 | date = June 2007 | pmid = 17581585 | doi = 10.1038/nature05854 | bibcode = 2007Natur.447.1003W | s2cid = 4334424 }}</ref> (Scientists identified an early Paleocene animal named ''[[Protungulatum donnae]]'' as one of the first placental mammals,<ref name="SCI-20130208">{{cite journal | vauthors = O'Leary MA, Bloch JI, Flynn JJ, Gaudin TJ, Giallombardo A, Giannini NP, Goldberg SL, Kraatz BP, Luo ZX, Meng J, Ni X, Novacek MJ, Perini FA, Randall ZS, Rougier GW, Sargis EJ, Silcox MT, Simmons NB, Spaulding M, Velazco PM, Weksler M, Wible JR, Cirranello AL | display-authors = 6 | title = The placental mammal ancestor and the post-K-Pg radiation of placentals | journal = Science | volume = 339 | issue = 6120 | pages = 662–667 | date = February 2013 | pmid = 23393258 | doi = 10.1126/science.1229237 | url = https://www.science.org/doi/abs/10.1126/science.1229237 | bibcode = 2013Sci...339..662O | hdl = 11336/7302 | s2cid = 206544776 | hdl-access = free | access-date = 30 June 2022 | archive-date = 10 November 2021 | archive-url = https://web.archive.org/web/20211110174432/https://www.science.org/doi/abs/10.1126/science.1229237 | url-status = live }}</ref> but it has since been reclassified as a non-placental eutherian.)<ref>{{cite journal | vauthors = Halliday TJ, Upchurch P, Goswami A | title = Resolving the relationships of Paleocene placental mammals | journal = Biological Reviews of the Cambridge Philosophical Society | volume = 92 | issue = 1 | pages = 521–550 | date = February 2017 | pmid = 28075073 | pmc = 6849585 | doi = 10.1111/brv.12242 }}</ref> Recalibrations of genetic and morphological diversity rates have suggested a [[Maastrichtian|Late Cretaceous]] origin for placentals, and a Paleocene origin for most modern clades.<ref>{{cite journal | vauthors = Halliday TJ, Upchurch P, Goswami A | title = Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous-Palaeogene mass extinction | journal = Proceedings. Biological Sciences| volume = 283 | issue = 1833 | pages = 20153026 | date = June 2016 | pmid = 27358361 | pmc = 4936024 | doi = 10.1098/rspb.2015.3026 }}</ref>

The earliest-known ancestor of primates is ''[[Archicebus achilles]]''<ref name="NTR-20130606">{{cite journal | vauthors = Ni X, Gebo DL, Dagosto M, Meng J, Tafforeau P, Flynn JJ, Beard KC | title = The oldest known primate skeleton and early haplorhine evolution | journal = Nature | volume = 498 | issue = 7452 | pages = 60–64 | date = June 2013 | pmid = 23739424 | doi = 10.1038/nature12200 | bibcode = 2013Natur.498...60N | s2cid = 4321956 }}</ref> from around 55&nbsp;million years ago.<ref name="NTR-20130606"/> This tiny primate weighed 20–30 grams (0.7–1.1 ounce) and could fit within a human palm.<ref name="NTR-20130606"/>

{{anchor|Anatomy and morphology}}