Editing Dinosaur (section)

===General description===
[[File:LA-Triceratops mount-2.jpg|thumb|upright=1.15|left|''[[Triceratops]]'' skeleton, [[Natural History Museum of Los Angeles County]]]]

Using one of the above definitions, dinosaurs can be generally described as [[archosaur]]s with [[Terrestrial locomotion#Posture|hind limbs held erect beneath the body]].<ref name=DFG97/> Other prehistoric animals, including [[pterosaur]]s, [[mosasaur]]s, [[ichthyosaur]]s, [[Plesiosauria|plesiosaurs]], and ''[[Dimetrodon]]'', while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs, being members of the clade [[Avemetatarsalia|Ornithodira]]. The other groups mentioned are, like dinosaurs and pterosaurs, members of [[Sauropsida]] (the reptile and bird clade), except ''Dimetrodon'' (which is a [[synapsid]]). None of them had the erect hind limb posture characteristic of true dinosaurs.<ref name=DL90/>

Dinosaurs were the dominant terrestrial vertebrates of the [[Mesozoic]] [[Era]], especially the Jurassic and Cretaceous periods. Other groups of animals were restricted in size and niches; [[mammal]]s, for example, rarely exceeded the size of a domestic cat and were generally rodent-sized carnivores of small prey.<ref name=MM97/> Dinosaurs have always been recognized as an extremely varied group: over 900 non-avian dinosaur genera have been confidently identified (2018)  with 1124 species (2016). Estimates put the total number of dinosaur genera preserved in the fossil record at 1850, nearly 75% still undiscovered,<ref name="Genera900">{{cite journal |last1=Tennant |first1=Jonathan P. |last2=Chiarenza |first2=Alfio Alessandro |last3=Baron |first3=Matthew |title=How has our knowledge of dinosaur diversity through geologic time changed through research history? |journal=PeerJ |date=19 February 2018 |volume=6 |pages=e4417 |doi=10.7717/peerj.4417|pmid=29479504 |pmc=5822849 |doi-access=free }}</ref><ref name="Howmany">{{cite journal |last1=Starrfelt |first1=Jostein |last2=Liow |first2=Lee Hsiang |title=How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=2016 |volume=371 |issue=1691 |article-number=20150219 |doi=10.1098/rstb.2015.0219|pmid=26977060 |pmc=4810813 }}</ref><ref name="Wang&Dodson"/> and the number that ever existed (in or out of the fossil record) at 3,400.<ref name=russell1995/> A 2016 estimate put the number of dinosaur species living in the Mesozoic at 1,543–2,468,<ref>{{cite journal |last1=Starrfelt |first1=Jostein |last2=Liow |first2=Lee Hsiang |year=2016 |title=How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model |journal=[[Philosophical Transactions of the Royal Society B]] |location=London |publisher=[[Royal Society]] |volume=371 |issue=1691 |article-number=20150219 |doi=10.1098/rstb.2015.0219 |issn=0962-8436 |pmc=4810813 |pmid=26977060}}</ref><ref>{{cite web |url=https://www.nationalgeographic.com/science/article/most-dinosaur-species-are-still-undiscovered/|url-status=live |url-access=registration |last=Black |first=Riley |title=Most Dinosaur Species Are Still Undiscovered |website=[[National Geographic News]] |date=March 23, 2016 |archive-url=https://web.archive.org/web/20210306214843/https://www.nationalgeographic.com/science/article/most-dinosaur-species-are-still-undiscovered/ |archive-date=March 6, 2021 |access-date=June 6, 2021}}</ref>  compared to the number of modern-day birds (avian dinosaurs) at 10,806 species.<ref>{{cite journal|last1=Gill|first1=F.|last2=Donsker|first2=D.|last3=Rasmussen|first3=P.|title=Welcome|year=2021|journal=IOC World Bird List 11.1.|url=https://www.worldbirdnames.org/new/|archive-date=July 30, 2023|access-date=January 25, 2021|archive-url=https://web.archive.org/web/20230730175525/https://www.worldbirdnames.org/new/|url-status=live}}</ref>

Extinct dinosaurs, as well as modern birds, include genera that are herbivorous and others carnivorous, including seed-eaters, fish-eaters, insectivores, and omnivores. While dinosaurs were ancestrally bipedal (as are all modern birds), some evolved into quadrupeds, and others, such as ''[[Anchisaurus]]'' and ''Iguanodon'', could walk as easily on two or four legs. Cranial modifications like horns and crests are common dinosaurian traits, and some extinct species had bony armor. Although the best-known genera are remarkable for their large size, many Mesozoic dinosaurs were human-sized or smaller, and modern birds are generally small in size. Dinosaurs today inhabit every continent, and fossils show that they had achieved global distribution by the [[Early Jurassic]] epoch at latest.<ref name=MacLeod>{{cite journal |last1=MacLeod |first1=Norman |last2=Rawson |first2=Peter F. |last3=Forey |first3=Peter L. |last4=Banner |first4=FT |last5=Boudagher-Fadel |first5=MK |last6=Bown |first6=PR |last7=Burnett |first7=JA |last8=Chambers |first8=P |last9=Culver |first9=S |last10=Evans |first10=SE |last11=Jeffery |first11=C |last12=Kaminski |first12=MA |last13=Lord |first13=AR |last14=Milner |first14=AC |last15=Milner |first15=AR |last16=Morris |first16=N |last17=Owen |first17=E |last18=Rosen |first18=BR |last19=Smith |first19=AB |last20=Taylor |first20=PD |last21=Urquhart |first21=E |last22=Young |first22=JR |display-authors=3 |year=1997 |title=The Cretaceous–Tertiary biotic transition |journal=[[Journal of the Geological Society]] |location=London |publisher=[[Geological Society of London]] |volume=154 |issue=2 |pages=265–292 |doi=10.1144/gsjgs.154.2.0265|bibcode=1997JGSoc.154..265M |s2cid=129654916 |issn=0016-7649}}</ref> Modern birds inhabit most available habitats, from terrestrial to marine, and there is evidence that some non-avian dinosaurs (such as ''[[Microraptor]]'') could fly or at least glide, and others, such as [[spinosauridae|spinosaurids]], had [[semiaquatic]] habits.<ref name=theropods/>