Cnemial crest on the tibia (protruding part of the top surface of the shinbone) arcs anterolaterally (curves to the front and the outer side) New revelations were supported by an increase in dinosaur discoveries. Major new dinosaur discoveries have been made by paleontologists working in previously unexplored regions, including India, South America, Madagascar, Antarctica, and most significantly China. Across theropods, sauropodomorphs, and ornithischians, the number of named genera began to increase exponentially in the 1990s. [21] As of 2008, [update] over 30 new species of dinosaurs were named each year. [66] At least sauropodomorphs experienced a further increase in the number of named species in the 2010s, with an average of 9.3 new species having been named each year between 2009 and 2020. As a consequence, more sauropodomorphs were named between 1990 and 2020 than in all previous years combined. [67] These new localities also led to improvements in overall specimen quality, with new species being increasingly named not on scrappy fossils but on more complete skeletons, sometimes from multiple individuals. Better specimens also led to new species being invalidated less frequently. [66] Asian localities have produced the most complete theropod specimens, [68] while North American localities have produced the most complete sauropodomorph specimens. [67] Based on fossil evidence from dinosaurs such as Oryctodromeus, some ornithischian species seem to have led a partially fossorial (burrowing) lifestyle. [174] Many modern birds are arboreal (tree climbing), and this was also true of many Mesozoic birds, especially the enantiornithines. [175] While some early bird-like species may have already been arboreal as well (including dromaeosaurids) such as Microraptor [176]) 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, [136] whether diplodocids could create sonic booms via whip-like tail snapping, [177] and whether sauropods could float. [178] Communication Morell, V. (1993). "Dino DNA: the Hunt and the Hype". Science. 261 (5118): 160–162. Bibcode: 1993Sci...261..160M. doi: 10.1126/science.8327889. PMID 8327889. a b c Novas, F.E.; Agnolin, F.L.; Ezcurra, M.D.; Müller, R.T.; Martinelli, A.; Langer, M. (2021). "Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications". Journal of South American Earth Sciences. 110: 103341. Bibcode: 2021JSAES.11003341N. doi: 10.1016/j.jsames.2021.103341. ISSN 0895-9811.

Langer, Max C.; Ferigolo, Jorge (January 1, 2013). "The Late Triassic dinosauromorph Sacisaurus agudoensis (Caturrita Formation; Rio Grande do Sul, Brazil): anatomy and affinities". Geological Society, London, Special Publications. 379 (1): 353–392. Bibcode: 2013GSLSP.379..353L. doi: 10.1144/SP379.16. ISSN 0305-8719. S2CID 131414332. Ceratosauria (generally elaborately horned carnivores that existed from the Jurassic to Cretaceous periods, originally included Coelophysoidea) Paleontologist Phil Senter has suggested that since non-avian dinosaurs did not have a syrinx, and their next closest living relatives, crocodilians, use the larynx, they could not vocalize as the common ancestor would have been mute. He states that they mostly on visual displays and possibly non-vocal acoustic sounds like hissing, jaw grinding or clapping, splashing and wing beating (possible in winged maniraptoran dinosaurs). [179] 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 rather than there being a "silent period" in bird evolution. [183]

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Zhang, F.; Kearns, S.L.; Orr, P.J.; Benton, M.J.; Zhou, Z.; Johnson, D.; Xu, X.; Wang, X. (2010). "Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds" (PDF). Nature. 463 (7284): 1075–1078. Bibcode: 2010Natur.463.1075Z. doi: 10.1038/nature08740. PMID 20107440. S2CID 205219587. While recent discoveries have made it more difficult to present a universally agreed-upon list of their distinguishing features, nearly all dinosaurs discovered so far share certain modifications to the ancestral archosaurian skeleton, or are clearly descendants of older dinosaurs showing these modifications. Although some later groups of dinosaurs featured further modified versions of these traits, they are considered typical for Dinosauria; the earliest dinosaurs had them and passed them on to their descendants. Such modifications, originating in the most recent common ancestor of a certain taxonomic group, are called the synapomorphies of such a group. [30] Labeled diagram of a typical archosaur skull, the skull of Dromaeosaurus Weishampel, Dodson & Osmólska 2004, pp.672–684, chpt. 30: "Dinosaur Extinction" by J. David Archibald and David E. Fastovsky.

Schweitzer, M.H.; Zheng, W.; Cleland, T.P.; Bern, M. (2013). "Molecular analyses of dinosaur osteocytes support the presence of endogenous molecules". Bone. Amsterdam: Elsevier. 52 (1): 414–423. doi: 10.1016/j.bone.2012.10.010. ISSN 8756-3282. PMID 23085295. Hadrosauriformes (ancestrally had a thumb spike; large quadrupedal herbivores, with teeth merged into dental batteries) Marsicano, C.A.; Irmis, R.B.; Mancuso, A.C.; Mundil, R.; Chemale, F. (2015). "The precise temporal calibration of dinosaur origins". Proceedings of the National Academy of Sciences. 113 (3): 509–513. Bibcode: 2016PNAS..113..509M. doi: 10.1073/pnas.1512541112. ISSN 0027-8424. PMC 4725541. PMID 26644579. Dyke & Kaiser 2011, chpt. 14: "Bird Evolution Across the K–Pg Boundary and the Basal Neornithine Diversification" by Bent E. K. Lindow. doi: 10.1002/9781119990475.ch14

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Farlow, James O.; Brett-Surman, M.K., eds. (1997). The Complete Dinosaur. Bloomington, IN: Indiana University Press. ISBN 978-0-253-33349-0. LCCN 97-23698. OCLC 924985811 . Retrieved October 14, 2019. Matthew G. Baron; Megan E. Williams (2018). "A re-evaluation of the enigmatic dinosauriform Caseosaurus crosbyensis from the Late Triassic of Texas, USA and its implications for early dinosaur evolution". Acta Palaeontologica Polonica. 63. doi: 10.4202/app.00372.2017.