Editing Mesozoic (section)

===Cretaceous===
The Cretaceous is the longest period of the Mesozoic, but has only two epochs: Early and Late Cretaceous.<ref name="Carl Fred Koch">{{cite encyclopedia|url=https://www.britannica.com/EBchecked/topic/142729/Cretaceous-Period/257709/Major-subdivisions-of-the-Cretaceous-System|title=Cretaceous|author=Carl Fred Koch|encyclopedia=britannica.com}}</ref> [[File:Knight Tylosaurus.jpg|thumb|''[[Tylosaurus]]'' (a [[mosasaur]]) hunting ''[[Xiphactinus]]'']]

The Early Cretaceous spans from 145 to 100&nbsp;million years ago.<ref name="Carl Fred Koch"/> The Early Cretaceous saw the expansion of seaways and a decline in diversity of sauropods, stegosaurs, and other high-browsing groups, with sauropods particularly scarce in North America.<ref name=ButlerEtal2009>{{cite journal |last1=Butler |first1=R. J. |last2=Barrett |first2=P. M. |last3=Kenrick |first3=P. |last4=Penn |first4=M. G. |title=Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution |journal=[[Journal of Evolutionary Biology]] |date=March 2009 |volume=22 |issue=3 |pages=446–459 |doi=10.1111/j.1420-9101.2008.01680.x |pmid=19210589 |s2cid=26000791 |doi-access=free }}</ref> {{citation needed span|Some island-hopping dinosaurs, such as ''[[Eustreptospondylus]]'', evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs rose up to fill the empty space that the Jurassic-Cretaceous extinction left behind, such as ''[[Carcharodontosaurus]]'' and ''[[Spinosaurus]]''.|date=March 2022}} Seasons came back into effect and the poles got seasonally colder, but some dinosaurs still inhabited the polar forests year round, such as ''[[Leaellynasaura]]'' and ''[[Muttaburrasaurus]]''. The poles were too cold for crocodiles, and became the last stronghold for large amphibians such as ''[[Koolasuchus]]''. Pterosaurs got larger as genera such as ''[[Tapejara (pterosaur)|Tapejara]]'' and ''[[Ornithocheirus]]'' evolved. Mammals continued to expand their range: [[eutriconodont]]s produced fairly large, [[wolverine]]-like predators such as ''[[Repenomamus]]'' and ''[[Gobiconodon]]'', early [[theria]]ns began to expand into [[metatheria]]ns and [[eutheria]]ns, and [[cimolodont]] [[multituberculate]]s went on to become common in the fossil record.

The Late Cretaceous spans from 100 to 66&nbsp;million years ago. The Late Cretaceous featured a cooling trend that would continue in the [[Cenozoic]] Era. Eventually, tropics were restricted to the equator and areas beyond the tropic lines experienced extreme seasonal changes in weather. Dinosaurs still thrived, as new taxa such as ''[[Tyrannosaurus]]'', ''[[Ankylosaurus]]'', ''[[Triceratops]]'' and [[hadrosaurs]] dominated the food web. In the oceans, [[mosasaurs]] ruled, filling the role of the ichthyosaurs, which, after declining, had disappeared in the [[Cenomanian-Turonian boundary event]]. Though [[pliosaur]]s had gone extinct in the same event, long-necked plesiosaurs such as ''[[Elasmosaurus]]'' continued to thrive. Flowering plants, possibly appearing as far back as the Triassic, became truly dominant for the first time. Pterosaurs in the Late Cretaceous declined for poorly understood reasons, though this might be due to tendencies of the fossil record, as their diversity seems to be much higher than previously thought. Birds became increasingly common and diversified into a variety of [[Enantiornithes|enantiornithe]] and [[Ornithurae|ornithurine]] forms. Though mostly small, marine [[hesperornithes]] became relatively large and flightless, adapted to life in the open sea. Metatherians and primitive eutherian also became common and even produced large and specialised genera such as ''[[Didelphodon]]'' and ''[[Schowalteria]]''. Still, the dominant mammals were multituberculates, [[cimolodont]]s in the north and [[gondwanathere]]s in the south. At the end of the Cretaceous, the [[Deccan traps]] and other volcanic eruptions were poisoning the atmosphere. As this continued, it is thought that a large meteor smashed into earth 66&nbsp;million years ago, creating the Chicxulub Crater in an event known as the [[Cretaceous–Paleogene extinction event|K-Pg Extinction]] (formerly K-T), the fifth and most recent mass extinction event, in which 75% of life became extinct, including all non-avian dinosaurs.<ref>{{cite journal |last1=Becker |first1=Luann |title=Repeated Blows|journal=[[Scientific American]] |volume=286 |issue=3 |date=2002 |pages=76–83 |doi=10.1038/scientificamerican0302-76 |pmid=11857903 |bibcode=2002SciAm.286c..76B}}</ref><ref>{{cite web|url=http://www.ucmp.berkeley.edu/mesozoic/cretaceous/cretaceous.php|title=Cretaceous|work=University of California}}</ref><ref>{{cite web|url=http://www.universetoday.com/36697/the-asteroid-that-killed-the-dinosaurs/|title=K-T Extinction event|author=Elizabeth Howell|work=Universe Today|date=3 February 2015}}</ref>