Editing Dinosaur (section)

==Paleobiology==
Knowledge about dinosaurs is derived from a variety of fossil and non-fossil records, including fossilized bones, [[feces]], [[Fossil trackway|trackway]]s, [[gastrolith]]s, [[feather]]s, impressions of skin, [[Organ (anatomy)|internal organ]]s and other [[soft tissue]]s.<ref name="softtissue">{{cite journal |last1=Dal Sasso |first1=Cristiano |author-link1=Cristiano Dal Sasso |last2=Signore |first2=Marco |date=March 26, 1998 |title=Exceptional soft-tissue preservation in a theropod dinosaur from Italy |journal=Nature |location=London |publisher=Nature Research |volume=392 |issue=6674 |pages=383–387 |doi=10.1038/32884 |bibcode=1998Natur.392..383D |s2cid=4325093 |issn=0028-0836|url=http://doc.rero.ch/record/14901/files/PAL_E2043.pdf |archive-url=https://web.archive.org/web/20160920170653/https://doc.rero.ch/record/14901/files/PAL_E2043.pdf |archive-date=2016-09-20 |url-status=live }}</ref><ref name="Schweitzer2005"/> Many fields of study contribute to our understanding of dinosaurs, including [[physics]] (especially [[biomechanics]]), [[chemistry]], [[biology]], and the [[Earth science]]s (of which [[paleontology]] is a sub-discipline).<ref name=alexander2006/><ref name=dinobiology>{{cite journal |last1=Farlow |first1=James O. |last2=Dodson |first2=Peter |last3=Chinsamy |first3=Anusuya |author-link3=Anusuya Chinsamy-Turan |date=November 1995 |title=Dinosaur Biology |journal=[[Annual Review of Ecology, Evolution, and Systematics|Annual Review of Ecology and Systematics]] |location=[[Palo Alto, California|Palo Alto, CA]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=26 |issue=1 |pages=445–471 |doi=10.1146/annurev.es.26.110195.002305 |bibcode=1995AnRES..26..445F |issn=1545-2069}}</ref> Two topics of particular interest and study have been dinosaur size and behavior.<ref>{{harvnb|Weishampel|Dodson|Osmólska|2004}}</ref>

===Size===
{{Main|Dinosaur size}}
[[File:Longest dinosaur by clade.svg|alt=|thumb|upright=1.35 |Scale diagram comparing the average human to the longest known dinosaurs in five major [[clade]]s:{{legend|#b1293a|[[Sauropoda]] (''[[Supersaurus|Supersaurus vivianae]]'')}}{{legend|#cf52cf|[[Ornithopod]]a (''[[Shantungosaurus|Shantungosaurus giganteus]]'')}}{{legend|#59ca4e|[[Theropoda]] (''[[Spinosaurus|Spinosaurus aegyptiacus]]'')}}
{{legend|#f89451|[[Thyreophora]] (''[[Stegosaurus|Stegosaurus ungulatus]]'')}}
{{legend|#2e538c|[[Marginocephalia]] (''[[Triceratops|Triceratops prorsus]]'')}}]]

Current evidence suggests that dinosaur average size varied through the Triassic, Early Jurassic, Late Jurassic and Cretaceous.<ref name=Sereno1999/> Predatory theropod dinosaurs, which occupied most terrestrial carnivore niches during the Mesozoic, most often fall into the {{convert|100|to|1000|kg|lb|abbr=on|adj=on}} category when sorted by estimated weight into categories based on [[order of magnitude]], whereas [[Holocene|recent]] predatory carnivoran mammals peak in the {{convert|10|to|100|kg|lb|abbr=on|adj=on}} category.<ref name=JF93/> The [[Mode (statistics)|mode]] of Mesozoic dinosaur body masses is between {{convert|1|and|10|MT|ST}}.<ref name=Peczkis1994/> This contrasts sharply with the average size of Cenozoic mammals, estimated by the [[National Museum of Natural History]] as about {{convert|2|to|5|kg|lb|abbr=on}}.<ref name=NMNH/>

The sauropods were the largest and heaviest dinosaurs. For much of the dinosaur era, the smallest sauropods were larger than anything else in their habitat, and the largest was an order of magnitude more massive than anything else that has since walked the Earth. Giant prehistoric mammals such as ''[[Paraceratherium]]'' (the largest land mammal ever) were dwarfed by the giant sauropods, and only modern whales approach or surpass them in size.<ref name="sander2011">{{cite journal |last1=Sander |first1=P. Martin |last2=Christian |first2=Andreas |last3=Clauss |first3=Marcus |last4=Fechner |first4=Regina |last5=Gee |first5=Carole T. |last6=Griebeler |first6=Eva-Maria |last7=Gunga |first7=Hanns-Christian |last8=Hummel |first8=Jürgen |last9=Mallison |first9=Heinrich |display-authors=3 |date=February 2011 |title=Biology of the sauropod dinosaurs: the evolution of gigantism |journal=Biological Reviews |location=Cambridge |publisher=Cambridge Philosophical Society |volume=86 |issue=1 |pages=117–155 |doi=10.1111/j.1469-185X.2010.00137.x |issn=1464-7931 |pmid=21251189 |pmc=3045712}}</ref> There are several proposed advantages for the large size of sauropods, including protection from predation, reduction of energy use, and longevity, but it may be that the most important advantage was dietary. Large animals are more efficient at digestion than small animals, because food spends more time in their digestive systems. This also permits them to subsist on food with lower nutritive value than smaller animals. Sauropod remains are mostly found in rock formations interpreted as dry or seasonally dry, and the ability to eat large quantities of low-nutrient browse would have been advantageous in such environments.<ref name=KC06/>

====Largest and smallest====
Scientists will probably never be certain of the [[largest organisms|largest and smallest dinosaurs]] to have ever existed. This is because only a tiny percentage of animals were ever fossilized and most of these remain buried in the earth. Few non-avian dinosaur specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar, better-known species is an inexact art, and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork.<ref>{{harvnb|Paul|2010}}</ref>

[[File:Argentinosaurus 9.svg|thumb|upright=1.15|left|Comparative size of ''[[Argentinosaurus]]'' to the average human]]

The tallest and heaviest dinosaur known from good skeletons is ''[[Giraffatitan|Giraffatitan brancai]]'' (previously classified as a species of ''[[Brachiosaurus]]''). Its remains were discovered in Tanzania between 1907 and 1912. Bones from several similar-sized individuals were incorporated into the skeleton now mounted and on display at the [[Natural History Museum, Berlin|Museum für Naturkunde]] in [[Berlin]];<ref name=EC68/> this mount is {{convert|12|m|ft|sp=us}} tall and {{convert|21.8|to|22.5|m|ft|sp=us}} long,<ref>{{cite journal |last1=Mazzetta |first1=Gerardo V. |last2=Christiansenb |first2=Per |last3=Fariñaa |first3=Richard A. |year=2004 |title=Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs |url=http://www.miketaylor.org.uk/tmp/papers/Mazzetta-et-al_04_SA-dino-body-size.pdf |archive-url=https://web.archive.org/web/20090225155217/http://www.miketaylor.org.uk/tmp/papers/Mazzetta-et-al_04_SA-dino-body-size.pdf |archive-date=2009-02-25 |url-status=live |journal=Historical Biology |location=Milton Park, Oxfordshire |publisher=Taylor & Francis |volume=16 |issue=2–4 |pages=71–83 |doi=10.1080/08912960410001715132 |bibcode=2004HBio...16...71M |citeseerx=10.1.1.694.1650 |s2cid=56028251 |issn=0891-2963}}</ref><ref>{{cite journal |last=Janensch |first=Werner |author-link=Werner Janensch |year=1950 |others=Translation by Gerhard Maier |title=Die Skelettrekonstruktion von ''Brachiosaurus brancai'' |trans-title=The Skeleton Reconstruction of Brachiosaurus brancai |url=https://paleoglot.org/files/Janensch1950b.pdf |url-status=live |journal=Palaeontographica |location=Stuttgart |publisher=[[E. Schweizerbart]] |volume=Suplement VII |issue=1. Reihe, Teil 3, Lieferung 2 |pages=97–103 |oclc=45923346 |archive-url=https://web.archive.org/web/20170711052046/https://paleoglot.org/files/Janensch1950b.pdf |archive-date=July 11, 2017 |access-date=October 24, 2019}}</ref> and would have belonged to an animal that weighed between {{gaps|30|000}} and {{gaps|60|000}}&nbsp;kilograms ({{gaps|70|000}} and {{gaps|130|000}}&nbsp;lb). The longest complete dinosaur is the {{convert|27|m|ft|sp=us}} long ''Diplodocus'', which was discovered in [[Wyoming]] in the [[United States]] and displayed in [[Pittsburgh]]'s [[Carnegie Museum of Natural History]] in 1907.<ref name=lucas04>{{cite conference |last1=Lucas |first1=Spencer G. |last2=Herne |first2=Matthew C. |last3=Hecket |first3=Andrew B. |last4=Hunt |first4=Adrian P. |last5=Sullivan |first5=Robert M. |display-authors=3 |year=2004 |title=Reappraisal of ''Seismosaurus'', a Late Jurassic Sauropod Dinosaur From New Mexico |url=https://gsa.confex.com/gsa/2004AM/finalprogram/abstract_77727.htm |url-status=live |conference=2004 Denver Annual Meeting (November 7–10, 2004) |conference-url=https://gsa.confex.com/gsa/2004AM/webprogram/start.html |volume=36 |publisher=Geological Society of America |location=Boulder, CO |page=422 |id=Paper No. 181-4 |oclc=62334058 |archive-url=https://web.archive.org/web/20191008110318/https://gsa.confex.com/gsa/2004AM/finalprogram/abstract_77727.htm |archive-date=October 8, 2019 |access-date=October 25, 2019}}</ref> The longest dinosaur known from good fossil material is ''[[Patagotitan]]'': the skeleton mount in the American Museum of Natural History in [[New York City|New York]] is {{convert|37|meters|feet}} long. The [[Museo Carmen Funes|Museo Municipal Carmen Funes]] in [[Plaza Huincul]], Argentina, has an ''[[Argentinosaurus]]'' reconstructed skeleton mount that is {{convert|39.7|m|feet|sp=us}} long.<ref name="PLOS One">{{cite journal |last1=Sellers |first1=William Irvin. |last2=Margetts |first2=Lee |last3=Coria |first3=Rodolfo Aníbal |author3-link=Rodolfo Coria |last4=Manning |first4=Phillip Lars |year=2013 |editor1-last=Carrier |editor1-first=David |title=March of the Titans: The Locomotor Capabilities of Sauropod Dinosaurs |doi=10.1371/journal.pone.0078733 |journal=PLOS ONE |location=San Francisco, CA |publisher=PLOS |volume=8 |issue=10 |page=e78733 |pmid=24348896 |pmc=3864407|bibcode=2013PLoSO...878733S |issn=1932-6203|doi-access=free }}</ref>
[[File:Maraapunisaurus Skeletal V1.svg|thumb|upright=1.15|left|''Maraapunisaurus'', one of the largest animals to walk the earth.]]
[[File:Bruhathkayosaurus matleyi updated.png|thumb|upright=1.15|right|''[[Bruhathkayosaurus]]'', potentially the largest terrestrial animal to ever exist.]]
There were larger dinosaurs, but knowledge of them is based entirely on a small number of fragmentary fossils. Most of the largest herbivorous specimens on record were discovered in the 1970s or later, and include the massive ''Argentinosaurus'', which may have weighed {{convert|80000|to|100000|kg|ST|sp=us|abbr=off|comma=gaps}} and reached lengths of {{convert|30|to|40|m|ft|sp=us}}; some of the longest were the {{convert|33.5|m|ft|sp=us|adj=mid}} long ''Diplodocus hallorum''<ref name=KC06/> (formerly ''Seismosaurus''), the {{convert|33|to|34|m|ft|sp=us|adj=mid}} long ''[[Supersaurus]]'',<ref name=LHW07/> and {{convert|37|m|feet|sp=us|adj=mid}} long ''Patagotitan''; and the tallest, the {{convert|18|m|ft|sp=us|adj=mid}} tall ''[[Sauroposeidon]]'', which could have reached a sixth-floor window. There were a few dinosaurs that was considered either the heaviest and longest. The most famous one include ''[[Amphicoelias fragillimus]]'', known only from a now lost partial vertebral [[Vertebra#Structure|neural arch]] described in 1878. Extrapolating from the illustration of this bone, the animal may have been {{convert|58|m|ft|sp=us}} long and weighed {{cvt|122400|kg|lb|comma=gaps}}.<ref name=KC06/> However, recent research have placed ''Amphicoelias'' from the long, gracile diplodocid to the shorter but much stockier rebbachisaurid. Now renamed as ''[[Maraapunisaurus]]'', this sauropod now stands as much as {{convert|40|m|ft|sp=us}} long and weigh as much as {{cvt|120000|kg|lb|comma=gaps}}.<ref name="carpenter2018">{{cite journal | title=Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado | author=Carpenter, Kenneth | journal=Geology of the Intermountain West | year=2018 | volume=5 | pages=227–244 | doi=10.31711/giw.v5i0.28 | doi-access=free }}</ref><ref>{{Cite journal|last=Paul|first=Gregory S.|date=2019|title=Determining the largest known land animal: A critical comparison of differing methods for restoring the volume and mass of extinct animals|url=http://www.gspauldino.com/Titanomass.pdf|journal=Annals of the Carnegie Museum|volume=85|issue=4|pages=335–358|doi=10.2992/007.085.0403|bibcode=2019AnCM...85..335P|s2cid=210840060|archive-date=January 28, 2020|access-date=December 2, 2023|archive-url=https://web.archive.org/web/20200128092205/http://www.gspauldino.com/Titanomass.pdf|url-status=live}}</ref> Another contender of this title includes ''[[Bruhathkayosaurus]]'', a controversial taxon that was recently confirmed to exist after archived photos were uncovered.<ref>{{Cite journal |last1=Pal |first1=Saurabh |last2=Ayyasami |first2=Krishnan |date=27 June 2022 |title=The lost titan of Cauvery |journal=[[Geology Today]] |language=en |volume=38 |issue=3 |pages=112–116 |doi=10.1111/gto.12390 |bibcode=2022GeolT..38..112P |s2cid=250056201 |issn=0266-6979}}</ref> ''Bruhathkayosaurus'' was a titanosaur and would have most likely weighed more than even ''Marrapunisaurus''. Recent size estimates in 2023 have placed this sauropod reaching lengths of up to {{cvt|44|m|ft}} long and a colossal weight range of around {{cvt|110000–170000|kg|lb|comma=gaps}}, if these upper estimates up true, ''Bruhathkayosaurus'' would have rivaled the ''[[blue whale]]'' and ''[[Perucetus colossus]]'' as one of the largest animals to have ever existed.<ref name="Bruhathkayosaurus2023">{{Cite journal |last1=Paul |first1=Gregory S. |last2=Larramendi |first2=Asier |date=11 April 2023 |title=Body mass estimate of ''Bruhathkayosaurus'' and other fragmentary sauropod remains suggest the largest land animals were about as big as the greatest whales |journal=Lethaia |language=en |volume=56 |issue=2 |pages=1–11 |doi=10.18261/let.56.2.5 |bibcode=2023Letha..56..2.5P |s2cid=259782734 |issn=0024-1164|doi-access=free }}</ref>

The largest carnivorous dinosaur was ''[[Spinosaurus]]'', reaching a length of {{convert|12.6|to|18|m|ft|sp=us}} and weighing {{convert|7|to|20.9|MT|ST}}.<ref name=SMBM06/><ref name=TH07/> Other large carnivorous theropods included ''[[Giganotosaurus]]'', ''[[Carcharodontosaurus]]'', and ''Tyrannosaurus''.<ref name=TH07/> ''[[Therizinosaurus]]'' and ''[[Deinocheirus]]'' were among the tallest of the theropods. The largest ornithischian dinosaur was probably the hadrosaurid ''[[Shantungosaurus|Shantungosaurus giganteus]]'' which measured {{convert|16.6|m|feet|sp=us}}.<ref>{{cite journal |last1=Zhao |first1=Xijin |author1-link=Zhao Xijin |last2=Li |first2=Dunjing |last3=Han |first3=Gang |last4=Zhao |first4=Huaxi |last5=Liu |first5=Fengguang |last6=Li |first6=Laijin |last7=Fang |first7=Xiaosi |display-authors=3 |year=2007 |title=Zhuchengosaurus maximus from Shandong Province |journal=Acta Geoscientia Sinica |location=[[Beijing]] |publisher=[[Chinese Academy of Geological Sciences]] |volume=28 |issue=2 |pages=111–122 |issn=1006-3021}}</ref> The largest individuals may have weighed as much as {{convert|16|MT|ST}}.<ref>{{harvnb|Weishampel|Dodson|Osmólska|2004|pp=438–463|loc=chpt. 20: "Hadrosauridae" by John R. Horner David B. Weishampel, and Catherine A. Forster.}}</ref>

[[File:Bee hummingbird (Mellisuga helenae) adult male in flight-cropped.jpg|thumb|An adult [[bee hummingbird]], the smallest known dinosaur]]
The smallest dinosaur known is the [[bee hummingbird]],<ref>{{harvnb|Norell|Gaffney|Dingus|2000}}</ref> with a length of only {{convert|5|cm|in|sp=us}} and mass of around {{convert|1.8|g|oz|abbr=on}}.<ref>{{cite web |url=https://www.birds.com/species/a-b/bee-hummingbird/ |url-status=live |title=Bee Hummingbird (''Mellisuga helenae'') |website=Birds.com |publisher=Paley Media |archive-url=https://web.archive.org/web/20150403005328/https://www.birds.com/species/a-b/bee-hummingbird/ |archive-date=April 3, 2015 |access-date=October 27, 2019}}</ref> The smallest known non-[[Avialae|avialan]] dinosaurs were about the size of [[pigeon]]s and were those theropods most closely related to birds.<ref name=zhang2008/> For example, ''[[Anchiornis huxleyi]]'' is currently the smallest non-avialan dinosaur described from an adult specimen, with an estimated weight of {{convert|110|g|oz|abbr=on}}<ref name=anchiadvance/> and a total skeletal length of {{convert|34|cm|ft|sp=us}}.<ref name=zhang2008/><ref name=anchiadvance/> The smallest herbivorous non-avialan dinosaurs included ''[[Microceratus]]'' and ''[[Wannanosaurus]]'', at about {{convert|60|cm|ft|sp=us}} long each.<ref name=Holtz2007/><ref name="butler&zhao2009"/>

===Behavior===
[[File:Maiasaurusnest.jpg|thumb|left|A nesting ground of the hadrosaur ''[[Maiasaura|Maiasaura peeblesorum]]'' was discovered in 1978]]

Many modern birds are highly social, often found living in flocks. There is general agreement that some behaviors that are common in birds, as well as in [[crocodilian]]s (closest living relatives of birds), were also common among extinct dinosaur groups. Interpretations of behavior in fossil species are generally based on the pose of skeletons and their [[Habitat (ecology)|habitat]], [[computer simulation]]s of their biomechanics, and comparisons with modern animals in similar ecological niches.<ref name=alexander2006/>

The first potential evidence for [[herd]]ing or [[Flocking (behavior)|flocking]] as a widespread behavior common to many dinosaur groups in addition to birds was the 1878 discovery of 31&nbsp;''Iguanodon'', ornithischians that were then thought to have perished together in [[Bernissart]], [[Belgium]], after they fell into a deep, flooded [[sinkhole]] and drowned.<ref name=Yans/> Other mass-death sites have been discovered subsequently. Those, along with multiple trackways, suggest that gregarious behavior was common in many early dinosaur species. Trackways of hundreds or even thousands of herbivores indicate that duck-billed (hadrosaurids) may have moved in great herds, like the [[American bison]] or the African [[springbok]]. Sauropod tracks document that these animals traveled in groups composed of several different species, at least in [[Oxfordshire]], England,<ref name=Day2002/> although there is no evidence for specific herd structures.<ref name=JLW05/> Congregating into herds may have evolved for defense, for [[Bird migration|migratory]] purposes, or to provide protection for young. There is evidence that many types of slow-growing dinosaurs, including various theropods, sauropods, ankylosaurians, ornithopods, and ceratopsians, formed aggregations of immature individuals. One example is a site in [[Inner Mongolia]] that has yielded remains of over 20 ''[[Sinornithomimus]]'', from one to seven years old. This assemblage is interpreted as a social group that was trapped in mud.<ref name=DVetal08sino/> The interpretation of dinosaurs as gregarious has also extended to depicting carnivorous theropods as [[pack hunter]]s working together to bring down large prey.<ref name=LG93/><ref name="maxwell&ostrom1995"/> However, this lifestyle is uncommon among modern birds, crocodiles, and other reptiles, and the [[taphonomy|taphonomic]] evidence suggesting mammal-like pack hunting in such theropods as ''Deinonychus'' and ''[[Allosaurus]]'' can also be interpreted as the results of fatal disputes between feeding animals, as is seen in many modern diapsid predators.<ref name=RB07/>

[[File:Centrosaurus dinosaur.png|thumb|upright=1.15|Restoration of two ''[[Centrosaurus|Centrosaurus apertus]]'' engaged in [[intra-specific combat]]]]
The crests and frills of some dinosaurs, like the [[marginocephalia]]ns, theropods and [[Lambeosaurinae|lambeosaurine]]s, may have been too fragile to be used for active defense, and so they were likely used for sexual or aggressive displays, though little is known about dinosaur mating and [[territory (animal)|territorialism]]. Head wounds from bites suggest that theropods, at least, engaged in active aggressive confrontations.<ref name=PC98/>

From a behavioral standpoint, one of the most valuable dinosaur fossils was discovered in the [[Gobi Desert]] in 1971. It included a ''[[Velociraptor]]'' attacking a ''[[Protoceratops]]'',<ref name=AMNH/> providing evidence that dinosaurs did indeed attack each other.<ref name=carpenter1998/> Additional evidence for attacking live prey is the partially healed tail of an ''[[Edmontosaurus]]'', a hadrosaurid dinosaur; the tail is damaged in such a way that shows the animal was bitten by a tyrannosaur but survived.<ref name=carpenter1998/> [[Cannibalism (zoology)|Cannibalism]] amongst some species of dinosaurs was confirmed by tooth marks found in [[Madagascar]] in 2003, involving the theropod ''[[Majungasaurus]]''.<ref name=rogersetal2003/>

Comparisons between the [[sclerotic ring|scleral rings]] of dinosaurs and modern birds and reptiles have been used to infer daily activity patterns of dinosaurs. Although it has been suggested that most dinosaurs were active during the day, these comparisons have shown that small predatory dinosaurs such as dromaeosaurids, ''[[Juravenator]]'', and ''[[Megapnosaurus]]'' were likely [[nocturnal]]. Large and medium-sized herbivorous and omnivorous dinosaurs such as ceratopsians, sauropodomorphs, hadrosaurids, ornithomimosaurs may have been [[cathemeral]], active during short intervals throughout the day, although the small ornithischian ''[[Agilisaurus]]'' was inferred to be [[Diurnality|diurnal]].<ref name=SchmitzMotani2011/>

Based on fossil evidence from dinosaurs such as ''[[Oryctodromeus]]'', some ornithischian species seem to have led a partially [[fossorial]] (burrowing) lifestyle.<ref name=VMK07/> Many modern birds are [[arboreal]] (tree climbing), and this was also true of many Mesozoic birds, especially the enantiornithines.<ref>{{harvnb|Chiappe|Witmer|2002}}</ref> While some early bird-like species may have already been arboreal as well (including dromaeosaurids) such as ''Microraptor''<ref name=chatterjee2007/>) most non-avialan dinosaurs seem to have relied on land-based locomotion. A good understanding of how dinosaurs moved on the ground is key to models of dinosaur behavior; the science of biomechanics, pioneered by [[Robert McNeill Alexander]], has provided significant insight in this area. For example, studies of the forces exerted by muscles and gravity on dinosaurs' skeletal structure have investigated how fast dinosaurs could run,<ref name=alexander2006/> whether [[diplodocid]]s could create [[sonic boom]]s via [[whip]]-like tail snapping,<ref name=goriely/> and whether sauropods could float.<ref name=Henderson2006/>

===Communication===
Modern birds [[Animal communication|communicate]] by visual and auditory signals, and the wide diversity of visual display structures among fossil dinosaur groups, such as horns, frills, crests, sails, and feathers, suggests that visual communication has always been important in dinosaur biology.<ref name=senter2008/> Reconstruction of the plumage color of ''Anchiornis'' suggest the importance of color in visual communication in non-avian dinosaurs.<ref name="Li2010"/> Vocalization in non-avian dinosaurs is less certain. In birds, the [[larynx]] plays no role in sound production. Instead, birds vocalize with a novel organ, the [[Syrinx (bird anatomy)|syrinx]], farther down the trachea.<ref name=":22"/> The earliest remains of a syrinx were found in a specimen of the duck-like ''[[Vegavis|Vegavis iaai]]'' dated 69 –66&nbsp;million years ago, and this organ is unlikely to have existed in non-avian dinosaurs.<ref name="Clarke2016"/> 
[[File:Lambeosaurus magnicristatus DB.jpg|thumb|Restoration of a striking and unusual visual display in a ''[[Lambeosaurus|Lambeosaurus magnicristatus]]''. The crest may also have acted as a resonating chamber for sounds.]]

On the basis that non-avian dinosaurs did not have syrinxes and that their next close living relatives, crocodilians, use the larynx, Phil Senter, a paleontologist, has suggested that the non-avians could not vocalize, because the common ancestor would have been mute. He states that they mostly on visual displays and possibly non-vocal sounds, such as hissing, jaw-grinding or -clapping, splashing, and wing-beating (possible in winged maniraptoran dinosaurs).<ref name=senter2008/> Other researchers have countered that vocalizations also exist in turtles, the closest relatives of archosaurs, suggesting that the trait is ancestral to their lineage. In addition, vocal communication in dinosaurs is indicated by the development of advanced hearing in nearly all major groups. Hence the syrinx may have supplemented and then replaced the larynx as a vocal organ, without a "silent period" in bird evolution.<ref name=":0" />

In 2023, a fossilized larynx was described, from a specimen of the ankylosaurid ''[[Pinacosaurus]]''. The structure was composed of [[cricoid cartilage|cricoid]] and [[arytenoid cartilage]]s, similar to those of non-avian reptiles; but the mobile cricoid–arytenoid joint and long arytenoid cartilages would have allowed air-flow control similar to that of birds, and thus could have made bird-like vocalizations. In addition, the cartilages were [[ossification|ossified]], implying that laryngeal ossification is a feature of some non-avian dinosaurs.<ref name=":1" /> A 2016 study concludes that some dinosaurs may have produced closed-mouth vocalizations, such as cooing, hooting, and booming. These occur in both reptiles and birds and involve inflating the esophagus or tracheal pouches. Such vocalizations evolved independently in extant archosaurs numerous times, following increases in body size.<ref name="Tobias2016"/> The crests of some hadrosaurids and the nasal chambers of ankylosaurids may have been [[acoustic resonance|resonators]].<ref name="Weishampel981"/><ref name="Witmer"/>

===Reproductive biology===
{{see also|Dinosaur egg}}
[[File:Gniazdo sieweczki RB.JPG|left|thumb|alt=Three bluish eggs with black speckling sit atop a layer of white mollusk shell pieces, surrounded by sandy ground and small bits of bluish stone|Nest of a [[plover]] (''[[Charadrius]]'')]]

All dinosaurs laid [[Amniote|amniotic egg]]s. Dinosaur eggs were usually laid in a nest. Most species create somewhat elaborate nests which can be cups, domes, plates, beds scrapes, mounds, or burrows.<ref name="Hansell">{{harvnb|Hansell|2000}}</ref> Some species of modern bird have no nests; the cliff-nesting [[Common murre|common guillemot]] lays its eggs on bare rock, and male [[emperor penguin]]s keep eggs between their body and feet. Primitive birds and many non-avialan dinosaurs often lay eggs in communal nests, with males primarily incubating the eggs. While modern birds have only one functional [[oviduct]] and lay one egg at a time, more primitive birds and dinosaurs had two oviducts, like crocodiles. Some non-avialan dinosaurs, such as ''[[Troodon]]'', exhibited iterative laying, where the adult might lay a pair of eggs every one or two days, and then ensured simultaneous hatching by delaying [[Broodiness#Broodiness in non-avian animals|brooding]] until all eggs were laid.<ref name="Varrichioetal.02">{{cite journal |last1=Varricchio |first1=David J. |last2=Horner |first2=John R. |last3=Jackson |first3=Frankie D. |year=2002 |title=Embryos and eggs for the Cretaceous theropod dinosaur ''Troodon formosus'' |journal=Journal of Vertebrate Paleontology |location=Milton Park, Oxfordshire |publisher=Taylor & Francis for the Society of Vertebrate Paleontology |volume=22 |issue=3 |pages=564–576 |doi=10.1671/0272-4634(2002)022[0564:EAEFTC]2.0.CO;2 |s2cid=85728452 |issn=0272-4634}}</ref>

When laying eggs, females grow a special type of bone between the hard outer bone and the [[Bone marrow|marrow]] of their limbs. This medullary bone, which is rich in [[calcium]], is used to make eggshells. A discovery of features in a ''Tyrannosaurus'' skeleton provided evidence of medullary bone in extinct dinosaurs and, for the first time, allowed paleontologists to establish the sex of a fossil dinosaur specimen. Further research has found medullary bone in the carnosaur ''Allosaurus'' and the ornithopod ''[[Tenontosaurus]]''. Because the line of dinosaurs that includes ''Allosaurus'' and ''Tyrannosaurus'' diverged from the line that led to ''Tenontosaurus'' very early in the evolution of dinosaurs, this suggests that the production of medullary tissue is a general characteristic of all dinosaurs.<ref name=LW08/>
[[File:Citipati AMNH.jpg|thumb|Fossil interpreted as a nesting [[oviraptoridae|oviraptorid]] ''[[Citipati]]'' at the [[American Museum of Natural History]]. ]]
Another widespread trait among modern birds (but see below in regards to fossil groups and extant [[megapodes]]) is parental care for young after hatching. [[Jack Horner (paleontologist)|Jack Horner's]] 1978 discovery of a ''[[Maiasaura]]'' ("good mother lizard") nesting ground in Montana demonstrated that parental care continued long after birth among ornithopods.<ref name=HM79/> A specimen of the [[oviraptoridae|oviraptorid]] ''[[Citipati|Citipati osmolskae]]'' was discovered in a [[Chicken#Broodiness|chicken-like brooding position]] in 1993,<ref name="search.eb"/> which may indicate that they had begun using an insulating layer of feathers to keep the eggs warm.<ref>{{harvnb|Currie|Koppelhus|Shugar|Wright|2004|pp=[http://thomas-hopp.com/pdf/DinoBrooding.pdf 234–250]|loc=chpt. 11: "Dinosaur Brooding Behavior and the Origin of Flight Feathers" by Thomas P. Hopp and Mark J. Orsen.}}</ref> An embryo of the basal sauropodomorph ''[[Massospondylus]]'' was found without teeth, indicating that some parental care was required to feed the young dinosaurs.<ref name=Reiszetal05/> Trackways have also confirmed parental behavior among ornithopods from the [[Isle of Skye]] in northwestern [[Scotland]].<ref name=BBCtracks/>

However, there is ample evidence of [[precociality]] or [[Precociality#Superprecociality|superprecociality]] among many dinosaur species, particularly theropods. For instance, non-[[Euornithes|ornithuromorph]] birds have been abundantly demonstrated to have had slow growth rates, [[megapode]]-like egg burying behavior and the ability to fly soon after birth.<ref>{{cite journal |first1=Zhonghe |last1=Zhou |first2=Fucheng |last2=Zhang |year=2004 |title=A Precocial Avian Embryo from the Lower Cretaceous of China |journal=Science |location=Washington, D.C. |publisher=American Association for the Advancement of Science |volume=306 |issue=5696 |page=653 |doi=10.1126/science.1100000 |issn=0036-8075 |pmid=15499011|s2cid=34504916 }}</ref><ref>{{cite journal |url=https://blogs.scientificamerican.com/tetrapod-zoology/drowned-cretaceous-bird-colony/ |url-status=live |title=A drowned nesting colony of Late Cretaceous birds |last=Naish |first=Darren |author-link=Darren Naish |date=May 15, 2012 |journal=Science |volume=306 |issue=5696 |page=653 |publisher=[[Scientific American#Website|Scientific American]] |doi=10.1126/science.1100000 |pmid=15499011 |s2cid=34504916 |archive-url=https://web.archive.org/web/20180925031243/https://blogs.scientificamerican.com/tetrapod-zoology/drowned-cretaceous-bird-colony/ |archive-date=September 25, 2018 |access-date=November 16, 2019}}</ref><ref>{{cite journal |last1=Fernández |first1=Mariela S. |last2=García |first2=Rodolfo A. |last3=Fiorelli |first3=Lucas |last4=Scolaro |first4=Alejandro |last5=Salvador |first5=Rodrigo B. |last6=Cotaro |first6=Carlos N. |last7=Kaiser |first7=Gary W. |last8=Dyke |first8=Gareth J. |author8-link=Gareth J. Dyke |display-authors=3 |year=2013 |title=A Large Accumulation of Avian Eggs from the Late Cretaceous of Patagonia (Argentina) Reveals a Novel Nesting Strategy in Mesozoic Birds |journal=PLOS ONE |location=San Francisco, CA |publisher=PLOS |volume=8 |issue=4 |page=e61030 |doi=10.1371/journal.pone.0061030 |pmid=23613776 |pmc=3629076 |bibcode=2013PLoSO...861030F |issn=1932-6203|doi-access=free }}</ref><ref>{{cite journal |last1=Deeming |first1=Denis Charles |last2=Mayr |first2=Gerald |author2-link=Gerald Mayr |date=May 2018 |title=Pelvis morphology suggests that early Mesozoic birds were too heavy to contact incubate their eggs |journal=[[Journal of Evolutionary Biology]] |location=Hoboken, NJ |publisher=Wiley-Blackwell on behalf of the [[European Society for Evolutionary Biology]] |volume=31 |issue=5 |pages=701–709 |doi=10.1111/jeb.13256 |pmid=29485191 |s2cid=3588317 |issn=1010-061X|url=http://eprints.lincoln.ac.uk/id/eprint/31436/13/31436%2031291%20Deeming_et_al-2018-Journal_of_Evolutionary_Biology.pdf |archive-url=https://web.archive.org/web/20200602094641/http://eprints.lincoln.ac.uk/id/eprint/31436/13/31436%2031291%20Deeming_et_al-2018-Journal_of_Evolutionary_Biology.pdf |archive-date=2020-06-02 |url-status=live }}</ref> Both ''Tyrannosaurus'' and ''Troodon'' had juveniles with clear superprecociality and likely occupying different ecological niches than the adults.<ref name="Varrichioetal.02"/> Superprecociality has been inferred for sauropods.<ref>{{cite journal |last1=Myers |first1=Timothy S. |last2=Fiorillo |first2=Anthony R. |year=2009 |title=Evidence for gregarious behavior and age segregation in sauropod dinosaurs |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |location=Amsterdam |publisher=Elsevier |volume=274 |issue=1–2 |pages=96–104 |doi=10.1016/j.palaeo.2009.01.002 |issn=0031-0182|bibcode=2009PPP...274...96M |url=http://doc.rero.ch/record/16633/files/PAL_E962.pdf |archive-url=https://web.archive.org/web/20200529011847/http://doc.rero.ch/record/16633/files/PAL_E962.pdf |archive-date=2020-05-29 |url-status=live }}</ref>

Genital structures are unlikely to fossilize as they lack scales that may allow preservation via pigmentation or residual calcium phosphate salts. In 2021, the best preserved specimen of a dinosaur's [[cloacal vent]] exterior was described for ''Psittacosaurus'', demonstrating lateral swellings similar to crocodylian musk glands used in social displays by both sexes and pigmented regions which could also reflect a signalling function. However, this specimen on its own does not offer enough information to determine whether this dinosaur had sexual signalling functions; it only supports the possibility. Cloacal visual signalling can occur in either males or females in living birds, making it unlikely to be useful to determine sex for extinct dinosaurs.<ref name="cloacal-vent">{{cite journal|doi=10.1016/j.cub.2020.12.039|title=A cloacal opening in a non-avian dinosaur|first1=Jakob|last1=Vinther|first2=Robert|last2=Nicholls|first3=Diane A.|last3=Kelly|journal=Current Biology|volume=31|pages=R1–R3|date=February 22, 2021|issue=4|publisher=Elsevier|pmid=33472049|s2cid=231644183|doi-access=free|bibcode=2021CBio...31.R182V }}</ref>

===Physiology===
{{Main|Physiology of dinosaurs}}
Because both modern crocodilians and birds have four-chambered hearts (albeit modified in crocodilians), it is likely that this is a trait shared by all archosaurs, including all dinosaurs.<ref name=CH04/> While all modern birds have high metabolisms and are [[endotherm]]ic ("warm-blooded"), a vigorous debate has been ongoing since the 1960s regarding how far back in the dinosaur lineage this trait extended. Various researchers have supported dinosaurs as being endothermic, [[ectotherm]]ic ("cold-blooded"), or somewhere in between.<ref name="pontzer2009">{{cite journal |last1=Pontzer |first1=H. |last2=Allen |first2=V. |last3=Hutchinson |first3=J.R. |year=2009 |title=Biomechanics of running indicates endothermy in bipedal dinosaurs |journal=PLOS ONE |volume=4 |issue=11 |page=e7783 |doi=10.1371/journal.pone.0007783 |doi-access=free |pmc=2772121 |pmid=19911059 |bibcode=2009PLoSO...4.7783P |issn=1932-6203}}</ref> An emerging consensus among researchers is that, while different lineages of dinosaurs would have had different metabolisms, most of them had higher metabolic rates than other reptiles but lower than living birds and mammals,<ref name="benson2018">{{cite journal |last1=Benson |first1=R.B.J. |year=2018 |title=Dinosaur Macroevolution and Macroecology |journal=Annual Review of Ecology, Evolution, and Systematics |volume=49 |pages=379–408 |doi=10.1146/annurev-ecolsys-110617-062231|s2cid=92837486 |doi-access=free }}</ref> which is termed [[mesotherm]]y by some.<ref name="grady2014">{{cite journal |last1=Grady |first1=J.M. |last2=Enquist |first2=B.J. |last3=Dettweiler-Robinson |first3=E. |last4=Wright |first4=N.A. |last5=Smith |first5=F.A. |year=2014 |title=Evidence for mesothermy in dinosaurs |journal=Science |volume=344 |issue=6189 |pages=1268–1272 |doi=10.1126/science.1253143|pmid=24926017 |bibcode=2014Sci...344.1268G |s2cid=9806780 }}</ref> Evidence from crocodiles and their extinct relatives suggests that such elevated metabolisms could have developed in the earliest archosaurs, which were the common ancestors of dinosaurs and crocodiles.<ref name="legendre2016">{{cite journal |last1=Legendre |first1=L.J. |last2=Guénard |first2=G. |last3=Botha-Brink |first3=J. |last4=Cubo |first4=J. |title=Palaeohistological Evidence for Ancestral High Metabolic Rate in Archosaurs |journal=Systematic Biology |year=2016 |volume=65 |issue=6 |pages=989–996 |doi=10.1093/sysbio/syw033|pmid=27073251 |doi-access=free }}</ref><ref name="seymour2004">{{cite journal |last1=Seymour |first1=R.S. |last2=Bennett-Stamper |first2=C.L. |last3=Johnston |first3=S.D. |last4=Carrier |first4=D.R. |last5=Grigg |first5=G.C. |year=2004 |title=Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution |journal=Physiological and Biochemical Zoology |volume=77 |issue=6 |pages=1051–1067 |doi=10.1093/sysbio/syw033|pmid=27073251 |doi-access=free }}</ref>

[[File:Pasta-Brontosaurus.jpg|thumb|left|This 1897 restoration of ''[[Brontosaurus]]'' as an aquatic, tail-dragging animal, by [[Charles R. Knight]], typified early views on dinosaur lifestyles.]]
After non-avian dinosaurs were discovered, paleontologists first posited that they were ectothermic. This was used to imply that the ancient dinosaurs were relatively slow, sluggish organisms, even though many modern reptiles are fast and light-footed despite relying on external sources of heat to regulate their body temperature. The idea of dinosaurs as ectothermic remained a prevalent view until [[Robert T. Bakker]], an early proponent of dinosaur endothermy, published an influential paper on the topic in 1968. Bakker specifically used anatomical and ecological evidence to argue that sauropods, which had hitherto been depicted as sprawling aquatic animals with their tails dragging on the ground, were endotherms that lived vigorous, terrestrial lives. In 1972, Bakker expanded on his arguments based on energy requirements and predator-prey ratios. This was one of the seminal results that led to the dinosaur renaissance.<ref name="bakker1968">{{cite journal |last1=Bakker |first1=R.T. |author-link=Robert T. Bakker |year=1968 |title=The Superiority of Dinosaurs |journal=Discovery: Magazine of the Peabody Museum of Natural History |volume=3 |issue=2 |pages=11–22 |issn=0012-3625 |oclc=297237777}}</ref><ref name="bakker1972">{{cite journal |last1=Bakker |first1=R.T. |author-link=Robert T. Bakker |year=1972 |title=Anatomical and Ecological Evidence of Endothermy in Dinosaurs |journal=Nature |volume=238 |issue=5359 |pages=81–85 |doi=10.1038/238081a0|bibcode=1972Natur.238...81B |s2cid=4176132 }}</ref><ref name="taylor2010"/><ref name="parsons2001"/>

One of the greatest contributions to the modern understanding of dinosaur physiology has been [[histology|paleohistology]], the study of microscopic tissue structure in dinosaurs.<ref name="erickson2014">{{cite journal |last1=Erickson |first1=G.M. |year=2014 |title=On dinosaur growth |journal=Annual Review of Earth and Planetary Sciences |volume=42 |issue=1 |pages=675–697 |doi=10.1146/annurev-earth-060313-054858|bibcode=2014AREPS..42..675E }}</ref><ref name="bailleul2019">{{cite journal |last1=Bailleul |first1=A.M. |last2=O'Connor |first2=J. |last3=Schweitzer |first3=M.H. |year=2019 |title=Dinosaur paleohistology: review, trends and new avenues of investigation |journal=PeerJ |volume=7 |page=e7764 |doi=10.7717/peerj.7764|pmid=31579624 |pmc=6768056 |doi-access=free }}</ref> From the 1960s forward, [[Armand de Ricqlès]] suggested that the presence of fibrolamellar bone—bony tissue with an irregular, fibrous texture and filled with blood vessels—was indicative of consistently fast growth and therefore endothermy. Fibrolamellar bone was common in both dinosaurs and pterosaurs,<ref name="dericqles1974">{{cite journal |last1=De Ricqlès |first1=A. |year=1974 |title=Evolution of endothermy: histological evidence |journal=Evolutionary Theory |volume=1 |issue=2 |pages=51–80 |url=http://www.stuartsumida.com/BIOL622/Ricqles1974.pdf |archive-url=https://web.archive.org/web/20210417055907/http://www.stuartsumida.com/BIOL622/Ricqles1974.pdf |archive-date=2021-04-17 |url-status=live}}</ref><ref name="dericqles1980">{{cite book |last1=De Ricqlès |first1=A. |year=1980 |chapter=Tissue structures of dinosaur bone, functional significance and possible relation to dinosaur physiology |editor-last1=Thomas |editor-first1=R.D.K. |editor-last2=Olson |editor-first2=E.C. |title=A Cold Look at the Warm-Blooded Dinosaurs |location=New York |publisher=American Association for the Advancement of Science |pages=103–139}}</ref> though not universally present.<ref name="padian2004">{{cite journal |last1=Padian |first1=K. |last2=Horner |first2=J.R. |last3=de Ricqlès |first3=A. |year=2004 |title=Growth in small dinosaurs and pterosaurs: the evolution of archosaurian growth strategies |journal=Journal of Vertebrate Paleontology |volume=24 |issue=3 |pages=555–571 |doi=10.1671/0272-4634(2004)024[0555:GISDAP]2.0.CO;2 |s2cid=86019906 |url=http://doc.rero.ch/record/15191/files/PAL_E2467.pdf |archive-date=February 4, 2023 |access-date=January 3, 2023 |archive-url=https://web.archive.org/web/20230204094637/https://doc.rero.ch/record/15191/files/PAL_E2467.pdf |url-status=live }}</ref><ref name="desouza2020">{{cite journal |last1=de Souza |first1=G.A. |last2=Bento Soares |first2=M. |last3=Souza Brum |first3=A. |last4=Zucolotto |first4=M. |last5=Sayão |first5=J.M. |last6=Carlos Weinschütz |first6=L. |last7=Kellner |first7=A.W.A. |year=2020 |title=Osteohistology and growth dynamics of the Brazilian noasaurid ''Vespersaurus paranaensis'' Langer et al., 2019 (Theropoda: Abelisauroidea) |journal=PeerJ |volume=8 |pages=e9771 |doi=10.7717/peerj.9771 |pmid=32983636 |pmc=7500327 |s2cid=221906765 |doi-access=free }}</ref> This has led to a significant body of work in reconstructing [[growth curve (biology)|growth curves]] and modeling the evolution of growth rates across various dinosaur lineages,<ref name="physiologyrefs">For examples of this work conducted on different dinosaur lineages, see

* {{cite journal |last1=Erickson |first1=G.M. |last2=Tumanova |first2=T.A. |year=2000 |title=Growth curve of ''Psittacosaurus mongoliensis'' Osborn (Ceratopsia: Psittacosauridae) inferred from long bone histology |journal=Zoological Journal of the Linnean Society |volume=130 |issue=4 |pages=551–566 |doi=10.1111/j.1096-3642.2000.tb02201.x |s2cid=84241148}}
* {{cite journal |last1=Erickson |first1=G. |last2=Rogers |first2=K. |last3=Yerby |first3=S. |year=2001 |title=Dinosaurian growth patterns and rapid avian growth rates |journal=Nature |volume=412 |issue=429–433 |pages=429–433 |bibcode=2001Natur.412..429E |doi=10.1038/35086558 |pmid=11473315 |s2cid=4319534}}{{Erratum|doi=10.1038/nature16488|pmid=26675731|http://retractionwatch.com/2016/03/01/high-profile-critic-slams-nature-letters-about-dinosaur-growth-following-corrections/ ''Retraction Watch''|checked=yes}}
* {{cite journal |last1=Erickson |first1=G. |last2=Makovicky |first2=P. |last3=Currie |first3=P. |last4=Norell |first4=M.A. |last5=Yerby |first5=S.A. |last6=Brochu |first6=C.A. |year=2004 |title=Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs |url=http://doc.rero.ch/record/15279/files/PAL_E2578.pdf |url-status=live |journal=Nature |volume=430 |issue=7001 |pages=772–775 |bibcode=2004Natur.430..772E |doi=10.1038/nature02699 |pmid=15306807 |s2cid=4404887 |archive-url=https://web.archive.org/web/20200714024211/http://doc.rero.ch/record/15279/files/PAL_E2578.pdf |archive-date=2020-07-14 }}{{Erratum|doi=10.1038/nature16487|pmid=26675726|http://retractionwatch.com/2016/03/01/high-profile-critic-slams-nature-letters-about-dinosaur-growth-following-corrections/ ''Retraction Watch''|checked=yes}}
* {{cite journal |last1=Lehman |first1=T.M. |last2=Woodward |first2=H.N. |year=2008 |title=Modeling growth rates for sauropod dinosaurs |url=http://doc.rero.ch/record/16723/files/PAL_E3766.pdf |journal=Paleobiology |volume=34 |issue=2 |pages=264–281 |doi=10.1666/0094-8373(2008)034[0264:MGRFSD]2.0.CO;2 |s2cid=84163725 |archive-date=February 4, 2023 |access-date=January 3, 2023 |archive-url=https://web.archive.org/web/20230204092325/https://doc.rero.ch/record/16723/files/PAL_E3766.pdf |url-status=live }}
* {{cite journal |last1=Horner |first1=J.R. |last2=de Ricqles |first2=A. |last3=Padian |first3=K. |last4=Scheetz |first4=R.D. |year=2009 |title=Comparative long bone histology and growth of the "hypsilophodontid" dinosaurs ''Orodromeus makelai'', ''Dryosaurus altus'', and ''Tenontosaurus tillettii'' (Ornithischia: Euornithopoda) |journal=Journal of Vertebrate Paleontology |volume=29 |issue=3 |pages=734–747 |bibcode=2009JVPal..29..734H |doi=10.1671/039.029.0312 |s2cid=86277619}}
* {{cite journal |last1=Woodward |first1=H. |last2=Freedman Fowler |first2=E. |last3=Farlow |first3=J. |last4=Horner |first4=J. |year=2015 |title=''Maiasaura'', a model organism for extinct vertebrate population biology: A large sample statistical assessment of growth dynamics and survivorship |journal=Paleobiology |volume=41 |issue=4 |pages=503–527 |bibcode=2015Pbio...41..503W |doi=10.1017/pab.2015.19 |s2cid=85902880}}</ref> which has suggested overall that dinosaurs grew faster than living reptiles.<ref name="bailleul2019"/> Other lines of evidence suggesting endothermy include the presence of feathers and other types of body coverings in many lineages (see {{section link||Feathers}}); more consistent ratios of the isotope [[oxygen-18]] in bony tissue compared to ectotherms, particularly as latitude and thus air temperature varied, which suggests stable internal temperatures<ref name="amiot2006">{{cite journal |last1=Amiot |first1=R. |last2=Lécuyer |first2=C. |last3=Buffetaut |first3=E. |last4=Escarguel |first4=G. |last5=Fluteau |first5=F. |last6=Martineau |first6=F. |year=2006 |title=Oxygen isotopes from biogenic apatites suggest widespread endothermy in Cretaceous dinosaurs |journal=Earth and Planetary Science Letters |volume=246 |issue=1–2 |pages=41–54 |doi=10.1016/j.epsl.2006.04.018|bibcode=2006E&PSL.246...41A |url=http://doc.rero.ch/record/14262/files/PAL_E2159.pdf }}</ref><ref name="amiot2010">{{cite journal |last1=Amiot |first1=R. |last2=Wang |first2=X. |last3=Lécuyer |first3=C. |last4=Buffetaut |first4=E. |last5=Boudad |first5=L. |last6=Cavin |first6=L. |last7=Ding |first7=Z. |last8=Fluteau |first8=F. |last9=Kellner |first9=A.W.A. |last10=Tong |first10=H. |last11=Zhang |first11=F. |year=2010 |title=Oxygen and carbon isotope compositions of middle Cretaceous vertebrates from North Africa and Brazil: ecological and environmental significance |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=297 |issue=2 |pages=439–451 |doi=10.1016/j.palaeo.2010.08.027|bibcode=2010PPP...297..439A }}</ref> (although these ratios can be altered during fossilization<ref name="kolodny1996">{{cite journal |last1=Kolodny |first1=Y. |last2=Luz |first2=B. |last3=Sander |first3=M. |last4=Clemens |first4=W.A. |year=1996 |title=Dinosaur bones: fossils or pseudomorphs? The pitfalls of physiology reconstruction from apatitic fossils |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=126 |issue=1–2 |pages=161–171 |doi=10.1016/S0031-0182(96)00112-5 |bibcode=1996PPP...126..161K |url=http://doc.rero.ch/record/14443/files/PAL_E1627.pdf |archive-date=February 4, 2023 |access-date=January 3, 2023 |archive-url=https://web.archive.org/web/20230204094527/https://doc.rero.ch/record/14443/files/PAL_E1627.pdf |url-status=live }}</ref>); and the discovery of [[South Polar region of the Cretaceous#Dinosaurs|polar dinosaurs]], which lived in Australia, Antarctica, and Alaska when these places would have had cool, temperate climates.<ref name="paul1988">{{cite journal |last1=Paul |first1=G.S. |year=1988 |title=Physiological, migratorial, climatological, geophysical, survival, and evolutionary implications of Cretaceous polar dinosaurs |journal=Journal of Paleontology |volume=62 |issue=4 |pages=640–652 |jstor=1305468|ref=none}}</ref><ref name="clemens1993">{{cite journal |last1=Clemens |first1=W.A. |last2=Nelms |first2=L.G. |year=1993 |title=Paleoecological implications of Alaskan terrestrial vertebrate fauna in latest Cretaceous time at high paleolatitudes |journal=Geology |volume=21 |issue=6 |pages=503–506 |doi=10.1130/0091-7613(1993)021<0503:PIOATV>2.3.CO;2|bibcode=1993Geo....21..503C }}</ref><ref name="rich2002">{{cite journal |last1=Rich |first1=T.H. |last2=Vickers-Rich |first2=P. |last3=Gangloff |first3=R.A. |year=2002 |title=Polar dinosaurs |journal=Science |volume=295 |issue=5557 |pages=979–980 |doi=10.1126/science.1068920|pmid=11834803 |s2cid=28065814 }}</ref><ref name="buffetaut2004">{{cite journal |last1=Buffetaut |first1=E. |year=2004 |title=Polar dinosaurs and the question of dinosaur extinction: a brief review |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=214 |issue=3 |pages=225–231 |doi=10.1016/j.palaeo.2004.02.050|url=http://doc.rero.ch/record/15383/files/PAL_E2734.pdf |archive-url=https://web.archive.org/web/20200608120307/http://doc.rero.ch/record/15383/files/PAL_E2734.pdf |archive-date=2020-06-08 |url-status=live }}</ref>

[[File:Dino bird h.jpg|thumb|Comparison between the [[air sac]]s of an [[abelisaur]] and a bird]]
In saurischian dinosaurs, higher metabolisms were supported by the evolution of the avian respiratory system, characterized by an extensive system of [[air sac]]s that extended the lungs and invaded many of the bones in the skeleton, making them hollow.<ref name=Sereno2008/> Such respiratory systems, which may have appeared in the earliest saurischians,<ref name="oconnor2009">{{cite journal |last1=O'Connor |first1=P.M. |year=2009 |title=Evolution of archosaurian body plans: skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs |journal=Journal of Experimental Zoology Part A: Ecological Genetics and Physiology |volume=311 |issue=8 |pages=629–646 |doi=10.1002/jez.548|pmid=19492308 |bibcode=2009JEZA..311..629O }}</ref> would have provided them with more oxygen compared to a mammal of similar size, while also having a larger resting [[tidal volume]] and requiring a lower breathing frequency, which would have allowed them to sustain higher activity levels.<ref name="sander2011"/> The rapid airflow would also have been an effective cooling mechanism, which in conjunction with a lower metabolic rate<ref name="eagle2011">{{cite journal |last1=Eagle |first1=R.A. |last2=Tütken |first2=T. |last3=Martin |first3=T.S. |last4=Tripati |first4=A.K. |last5=Fricke |first5=H.C. |last6=Connely |first6=M. |last7=Cifelli |first7=R.L. |last8=Eiler |first8=J.M. |year=2011 |title=Dinosaur body temperatures determined from isotopic (<sup>13</sup>C-<sup>18</sup>O) ordering in fossil biominerals |journal=Science |volume=333 |issue=6041 |pages=443–445 |pmid=21700837 |doi=10.1126/science.1206196 |bibcode=2011Sci...333..443E |s2cid=206534244}}</ref> would have prevented large sauropods from overheating. These traits may have enabled sauropods to grow quickly to gigantic sizes.<ref name="wedel2003">{{cite journal |last1=Wedel |first1=M.J. |year=2003 |title=Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs |journal=Paleobiology |volume=29 |issue=2 |pages=243–255 |doi=10.1017/S0094837300018091 |bibcode=2003Pbio...29..243W |url=http://doc.rero.ch/record/14872/files/PAL_E2010.pdf |archive-date=May 18, 2023 |access-date=January 3, 2024 |archive-url=https://web.archive.org/web/20230518003816/https://doc.rero.ch/record/14872/files/PAL_E2010.pdf |url-status=live }}</ref><ref name="perry2009">{{cite journal |last1=Perry |first1=S.F. |last2=Christian |first2=A. |last3=Breuer |first3=T. |last4=Pajor |first4=N. |last5=Codd |first5=J.R. |year=2009 |title=Implications of an avian-style respiratory system for gigantism in sauropod dinosaurs |journal=Journal of Experimental Zoology Part A: Ecological Genetics and Physiology |volume=311 |issue=8 |pages=600–610 |doi=10.1002/jez.517 |pmid=19189317|bibcode=2009JEZA..311..600P }}</ref> Sauropods may also have benefitted from their size—their small surface area to volume ratio meant that they would have been able to thermoregulate more easily, a phenomenon termed [[gigantothermy]].<ref name="sander2011"/><ref name="alexander1998">{{cite journal |last1=Alexander |first1=R.M. |year=1998 |title=All-time giants: the largest animals and their problems |journal=Palaeontology |volume=41 |pages=1231–1245 |url=https://www.palass.org/publications/palaeontology-journal/archive/41/6/article_pp1231-1245 |archive-date=September 27, 2016 |access-date=January 2, 2021 |archive-url=https://web.archive.org/web/20160927060250/https://www.palass.org/publications/palaeontology-journal/archive/41/6/article_pp1231-1245 |url-status=live }}</ref>

Like other reptiles, dinosaurs are primarily [[uricotelic]], that is, their [[kidney]]s extract nitrogenous wastes from their bloodstream and excrete it as [[uric acid]] instead of [[urea]] or [[ammonia]] via the ureters into the intestine. This would have helped them to conserve water.<ref name="benson2018"/> In most living species, uric acid is excreted along with feces as a semisolid waste.<ref name="tsahar2005">{{cite journal |last1=Tsahar |first1=E. |last2=Martínez del Rio |first2=C. |last3=Izhaki |first3=I. |last4=Arad |first4=Z. |year=2005 |title=Can birds be ammonotelic? Nitrogen balance and excretion in two frugivores |journal=[[The Journal of Experimental Biology]] |volume=208 |issue=6 |pages=1025–1034 |url= https://jeb.biologists.org/content/jexbio/208/6/1025.full.pdf |url-status=live |doi=10.1242/jeb.01495 |issn=0022-0949 |pmid=15767304 |bibcode=2005JExpB.208.1025T |s2cid=18540594 |archive-url=https://web.archive.org/web/20191017110333/https://jeb.biologists.org/content/jexbio/208/6/1025.full.pdf |archive-date=October 17, 2019 |access-date=October 31, 2019}}</ref><ref name="skadhauge2003">{{cite journal |last1=Skadhauge |first1=E. |last2=Erlwanger |first2=K.H. |last3=Ruziwa |first3=S.D. |last4=Dantzer |first4=V. |last5=Elbrønd |first5=V.S. |last6=Chamunorwa |first6=J.P. |year=2003 |title=Does the ostrich (''Struthio camelus'') coprodeum have the electrophysiological properties and microstructure of other birds? |journal=[[Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology]] |volume=134 |issue=4 |pages=749–755 |doi=10.1016/S1095-6433(03)00006-0 |issn=1095-6433 |pmid=12814783}}</ref> However, at least some modern birds (such as [[hummingbird]]s) can be facultatively [[ammonotelic]], excreting most of the nitrogenous wastes as ammonia.<ref name="preest1997">{{cite journal |last1=Preest |first1=M.R. |last2=Beuchat |first2=C.A. |year=1997 |title=Ammonia excretion by hummingbirds |journal=Nature |volume=386 |issue=6625 |pages=561–562 |bibcode=1997Natur.386..561P |doi=10.1038/386561a0 |s2cid=4372695 |issn=0028-0836}}</ref> This material, as well as the output of the intestines, emerges from the [[cloaca]].<ref name="mora1965">{{cite journal |last1=Mora |first1=J. |last2=Martuscelli |first2=J. |last3=Ortiz Pineda |first3=J. |last4=Soberon |first4=G. |year=1965 |title=The Regulation of Urea-Biosynthesis Enzymes in Vertebrates |journal=[[Biochemical Journal]] |volume=96 |issue=1 |pages=28–35 |issn=0264-6021 |doi=10.1042/bj0960028 |pmc=1206904 |pmid=14343146}}</ref><ref name="packard1966">{{cite journal |last=Packard |first=G.C. |year=1966 |title=The Influence of Ambient Temperature and Aridity on Modes of Reproduction and Excretion of Amniote Vertebrates |journal=The American Naturalist |volume=100 |issue=916 |pages=667–682 |doi=10.1086/282459 |issn=0003-0147 |jstor=2459303 |bibcode=1966ANat..100..667P |s2cid=85424175}}</ref> In addition, many species regurgitate [[Pellet (ornithology)|pellets]],<ref name="balgooyen1971">{{cite journal |last=Balgooyen |first=T.G. |year=1971 |title=Pellet Regurgitation by Captive Sparrow Hawks (''Falco sparverius'') |journal=[[The Condor (journal)|Condor]] |volume=73 |issue=3 |pages=382–385 |jstor=1365774 |url=https://sora.unm.edu/sites/default/files/journals/condor/v073n03/p0382-p0385.pdf |doi=10.2307/1365774 |archive-url=https://web.archive.org/web/20190404001957/https://sora.unm.edu/sites/default/files/journals/condor/v073n03/p0382-p0385.pdf |archive-date=April 4, 2019 |access-date=October 30, 2019}}</ref> and fossil pellets are known as early as the Jurassic from ''[[Anchiornis]]''.<ref name="xu2018">{{cite journal |last1=Xu |first1=X. |last2=Li |first2=F. |last3=Wang |first3=Y. |last4=Sullivan |first4=C. |last5=Zhang |first5=F. |last6=Zhang |first6=X. |last7=Sullivan |first7=C. |last8=Wang |first8=X. |last9=Zheng |first9=X. |year=2018 |title=Exceptional dinosaur fossils reveal early origin of avian-style digestion |journal=Scientific Reports |volume=8 |issue=1 |page=14217 |doi=10.1038/s41598-018-32202-x |pmid=30242170 |issn=2045-2322 |pmc=6155034 |bibcode=2018NatSR...814217Z}}</ref>

{{anchor|intelligence}}The size and shape of the brain can be partly reconstructed based on the surrounding bones. In 1896, Marsh calculated ratios between brain weight and body weight of seven species of dinosaurs, showing that the brain of dinosaurs was proportionally smaller than in today's crocodiles, and that the brain of ''Stegosaurus'' was smaller than in any living land vertebrate. This contributed to the widespread public notion of dinosaurs as being sluggish and extraordinarily stupid. Harry Jerison, in 1973, showed that proportionally smaller brains are expected at larger body sizes, and that brain size in dinosaurs was not smaller than expected when compared to living reptiles.<ref name="russell1997"/> Later research showed that relative brain size progressively increased during the evolution of theropods, with the highest intelligence – comparable to that of modern birds – calculated for the troodontid ''Troodon''.<ref name="brusatte2012"/>