The Ultimate Dinosaur Encyclopedia

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Evolution of dinosaurs Dinosaur features [ change | change source ] Labeled diagram of a typical archosaur skull, the skull of Dromaeosaurus

Sereno PC (1999). "The evolution of dinosaurs". Science. 284 (5423): 2137–2147. doi: 10.1126/science.284.5423.2137. PMID 10381873. MacLeod, Norman; Rawson, Peter F.; Forey, Peter L.; etal. (1997). "The Cretaceous–Tertiary biotic transition". Journal of the Geological Society. London: Geological Society of London. 154 (2): 265–292. Bibcode: 1997JGSoc.154..265M. doi: 10.1144/gsjgs.154.2.0265. ISSN 0016-7649. S2CID 129654916.Comparisons between the 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 diurnal. [173] 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

The first dinosaur fossils were recognized in the early 19th century, with the name "dinosaur" (meaning "terrible lizard") being coined by Sir Richard Owen in 1842 to refer to these "great fossil lizards". [7] [8] [9] Since then, mounted fossil dinosaur skeletons have been major attractions at museums worldwide, and dinosaurs have become an enduring part of popular culture. The large sizes of some dinosaurs, as well as their seemingly monstrous and fantastic nature, have ensured their regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, and new discoveries are regularly covered by the media. Restoration of four macronarian sauropods: from left to right Camarasaurus, Brachiosaurus, Giraffatitan, and Euhelopus Nesbitt, Sterling J. 2011. The early evolution of Archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History. New York: American Museum of Natural History. 2011 (352): 1–292. doi:10.1206/352.1. hdl:2246/6112. ISSN 0003-0090. S2CID 83493714. Dinosaurs (including birds) are members of the natural group Reptilia. Their biology does not precisely correspond to the antiquated class Reptilia of Linnaean taxonomy, consisting of cold-blooded amniotes without fur or feathers. As Linnean taxonomy was formulated for modern animals prior to the study of evolution and paleontology, it fails to account for extinct animals with intermediate traits between traditional classes.Fourth trochanter (projection where the caudofemoralis muscle attaches on the inner rear shaft) on the femur (thigh bone) is a sharp flange Some other non-dinosaur reptiles are also archosaurs, including pterosaurs (the now-extinct flying reptiles) and modern crocodiles and their ancestors. The following is a simplified list of dinosaur groups based on their evolution. [8] Groups with a dagger (†) next to them don't have any living members. Owen, Richard (1842). "Report on British Fossil Reptiles. Part II". Report of the Eleventh Meeting of the British Association for the Advancement of Science; Held at Plymouth in July 1841. London: John Murray. pp. 60–204. ISBN 978-0-8201-1526-9. LCCN 99030427. OCLC 1015526268 . Retrieved October 13, 2019.

Alvarez, Walter (1997). T. rex and the Crater of Doom. Princeton, NJ: Princeton University Press. ISBN 978-0-691-01630-6. LCCN 96049208. OCLC 1007846558 . Retrieved November 4, 2019.

Scientists will probably never be certain of the 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 of the 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. [144] Comparative size of Argentinosaurus to the average human Heilmann, Gerhard (1926). The Origin of Birds. London; New York: H. F. & G. Witherby; D. Appleton & Company. LCCN 27001127. OCLC 606021642.