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Dinosaur size

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Scale diagram comparing a human and the largest-known dinosaurs of five major clades
An adult male bee hummingbird, the smallest known and the smallest living dinosaur

Size is an important aspect of dinosaur paleontology, of interest to both the general public and professional scientists. Dinosaurs show some of the most extreme variations in size of any land animal group, ranging from tiny hummingbirds, which can weigh as little as two grams, to the extinct titanosaurs, which could weigh as much as 50–100 t (55–110 short tons).

The latest evidence suggests that dinosaurs' average size varied through the Triassic, early Jurassic, late Jurassic and Cretaceous periods, and dinosaurs probably only became widespread during the early or mid Jurassic.[1] Predatory theropod dinosaurs, which occupied most terrestrial carnivore niches during the Mesozoic, most often fall into the 100–1,000 kg (220–2,200 lb) category when sorted by estimated weight into categories based on order of magnitude, whereas recent predatory carnivoran mammals peak in the range of 10–100 kg (22–220 lb).[2] The mode of Mesozoic dinosaur body masses is between one and ten metric tonnes.[3] This contrasts sharply with the size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kg (4.4 to 11.0 lb).[4]

Size estimation

Scientists will probably never be certain of the largest and smallest dinosaurs. This is because only a small fraction of animals ever fossilize, and most of these remain buried in the earth and will either never be uncovered, or will be unintentionally destroyed as a result of human activity. Of the specimens that are recovered, few are even relatively complete skeletons, and impressions of skin and other soft tissues are rarely discovered. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar, better-known species is an inexact art (though governed by some established allometric trends), and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork, and never perfect.[5] Mass estimates for dinosaurs are much more variable than length estimates, because estimating length for extinct animals is much more easily done from a skeleton than estimating mass, since muscle volume makes a much smaller difference. Estimating mass is most easily done with the laser scan skeleton technique that puts a "virtual" skin over it, but even this is only an estimate.[6]

Sauropodomorphs

size comparison of selected giant sauropod dinosaurs

Sauropodomorph size is difficult to estimate given their usually fragmentary state of preservation. Sauropods are often preserved without their tails, so the margin of error in overall length estimates is high. Mass is calculated using the cube of the length, so for species in which the length is particularly uncertain, the weight is even more so. Estimates that are particularly uncertain (due to very fragmentary or lost material) are preceded by a question mark. Each number represents the highest estimate of a given research paper. One large sauropod, Maraapunisaurus fragillimus, was based on particularly scant remains that have been lost since their description by paleontologists in 1878. Analysis of the illustrations included in the original report suggested that M. fragillimus may have been the largest land animal of all time, possibly weighing 100–150 t (110–170 short tons) and measuring between 40–60 m (130–200 ft) long.[7][8] One later analysis of the surviving evidence, and the biological plausibility of such a large land animal, suggested that the enormous size of this animal was an over-estimate due partly to typographical errors in the original report.[9] This would later be challenged by a different study, which argued Cope's measurements were genuine and there's no basis for assuming typographical errors. The study, however, also reclassified the species and correspondingly gave a much lower length estimate of 30.3 metres (99 ft) and a mass of 78.5 t (86.5 short tons).[10] This in itself would later be disputed as being too small for an animal of such size, with some believing it to be even larger at around 35–40 metres (115–131 ft) and weighing around 80–120 t (88–132 short tons).[11]

Generally, the giant sauropods can be divided into two categories: the shorter but stockier and more massive forms (mainly titanosaurs and some brachiosaurids), and the longer but slenderer and more light-weight forms (mainly diplodocids).

Because different methods of estimation sometimes give conflicting results, mass estimates for sauropods can vary widely causing disagreement among scientists over the accurate number. For example, the titanosaur Dreadnoughtus was originally estimated to weigh 59.3 tonnes by the allometric scaling of limb-bone proportions, whereas more recent estimates, based on three-dimensional reconstructions, yield a much smaller figure of 22.1–38.2 tonnes.[12]

Reconstructed skeleton of the titanosaur Argentinosaurus huinculensis, often considered the largest-known dinosaur

The sauropods were the longest and heaviest dinosaurs. For much of the dinosaur era, the smallest sauropods were larger than almost anything else in their habitat, and the largest were an order of magnitude more massive than anything else known to have walked the Earth since. Giant prehistoric mammals such as Paraceratherium and Palaeoloxodon (the largest land mammals ever discovered[13]) were dwarfed by the giant sauropods, and only modern whales approach or surpass them in weight, though they live in the oceans.[14] 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.[15]

One of the tallest and heaviest dinosaurs known from good skeletons is 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 Museum für Naturkunde Berlin;[16] this mount is 12–13.27 metres (39.4–43.5 ft) tall and 21.8–22.5 metres (72–74 ft) long,[17][18][19] and would have belonged to an animal that weighed between 30,000 to 60,000 kilograms (66,000 to 132,000 lb). One of the longest complete dinosaurs is the 27-metre-long (89 ft) Diplodocus, which was discovered in Wyoming in the United States and displayed in Pittsburgh's Carnegie Natural History Museum in 1907.[20]

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 titanosaur Argentinosaurus huinculensis, which is the largest dinosaur known from uncontroversial and relatively substantial evidence, estimated to have been 70–80 t (77–88 short tons) and 36 m (118 ft) long.[21][7] Some of the longest sauropods were those with exceptionally long, whip-like tails, such as the 29–30 m (95–98 ft) Diplodocus hallorum[7][21] (formerly Seismosaurus) and the 45 m (148 ft) Barosaurus.[21]

In 2014, the fossilized remains of a previously unknown species of sauropod were discovered in Argentina.[22] The titanosaur, named Patagotitan mayorum, was estimated to have been around 40 m (130 ft) long weighing around 77 t (85 short tons), larger than any other previously found sauropod. The specimens found were remarkably complete, significantly more so than previous titanosaurs. It since been suggested that Patagotitan was not necessarily larger than Argentinosaurus and Puertasaurus.[23] In 2019, Patagotitan was estimated to have been 31 metres (102 ft) long and 50–77 tonnes (110,000–170,000 lb) massive.[24]

The largest of non-sauropod sauropodomorphs was Euskelosaurus. It reached 12.2 m (40 ft) in length and 2 t (2.2 short tons) in weight.[25] Another large sauropodomorph Yunnanosaurus youngi reached 13 m (43 ft) long.[26]

Theropods

Size comparison of selected giant theropod dinosaurs

Tyrannosaurus was for many decades the largest and best-known theropod to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus, Carcharodontosaurus, and Giganotosaurus.[27] These large theropod dinosaurs are estimated to rival or even exceeded Tyrannosaurus rex in size, though more recent studies and reconstructions show that Tyrannosaurus, although shorter, was the bulkier animal overall. Specimens such as Sue and Scotty are both estimated to be the most massive theropods known to science. There is still no clear explanation for exactly why these animals grew so bulky and heavy compared to the land predators that came before and after them.

Skeleton of Giganotosaurus, one of the largest theropods known.

The largest extant theropod is the common ostrich, up to 2.74 metres (9 ft 0 in) tall and weighs between 63.5 and 145.15 kilograms (140.0 and 320.0 lb).[28]

The smallest non-avialan theropod known from adult specimens may be Anchiornis huxleyi, at 110 grams (3.9 ounces) in weight and 34 centimetres (13 in) in length.[29] However, some studies suggest that Anchiornis was actually an avialan.[30] The smallest dinosaur known from adult specimens which is definitely not an avialan is Parvicursor remotus, at 162 grams (5.7 oz) and measuring 39 centimetres (15 in) long.[31] However, in 2022 its holotype was recognized as a juvenile individual.[32] Among living dinosaurs, the bee hummingbird (Mellisuga helenae) is smallest at 1.9 g (0.067 oz) and 5.5 cm (2.2 in) long.[33]

Recent theories propose that theropod body size shrank continuously over the past 50 million years, from an average of 163 kilograms (359 lb) down to 0.8 kg (1.8 lb), as they eventually evolved into modern birds. This is based on evidence that theropods were the only dinosaurs to get continuously smaller, and that their skeletons changed four times faster than those of most other dinosaur species.[34][35]

See also

References

  1. ^ Sereno PC (1999). "The evolution of dinosaurs". Science. 284 (5423): 2137–2147. doi:10.1126/science.284.5423.2137. PMID 10381873.
  2. ^ Farlow JA (1993). "On the rareness of big, fierce animals: speculations about the body sizes, population densities, and geographic ranges of predatory mammals and large, carnivorous dinosaurs". In Dodson, Peter; Gingerich, Philip (eds.). Functional Morphology and Evolution. American Journal of Science, Special Volume. Vol. 293-A. pp. 167–199.
  3. ^ Peczkis, J. (1994). "Implications of body-mass estimates for dinosaurs". Journal of Vertebrate Paleontology. 14 (4): 520–33. doi:10.1080/02724634.1995.10011575.
  4. ^ "Anatomy and evolution". National Museum of Natural History. Archived from the original on 2007-11-11. Retrieved 2007-11-21.
  5. ^ Paul, Gregory S. (2010). Princeton Field Guide to Dinosaurs. Princeton University Press. ISBN 978-0-691-13720-9.
  6. ^ Strauss, Bob."Why Were Dinosaurs So Big? The Facts and Theories Behind Dinosaur Gigantism". About EducationArchived 2014-10-06 at the Wayback Machine
  7. ^ a b c Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs: 2nd Edition. United States of America: Princeton University Press. ISBN 978-0-691-16766-4.
  8. ^ Paul, G.S. (1997). "Dinosaur models: the good, the bad, and using them to estimate the mass of dinosaurs" (PDF). In Wolberg, D.L.; Stump, E.; Rosenberg, G.D. (eds.). DinoFest International Proceedings. Dinofest International. The Academy of Natural Sciences. pp. 129–154. Archived (PDF) from the original on March 4, 2016.
  9. ^ Woodruff, C; Foster, JR (2015). "The fragile legacy of Amphicoelias fragillimus (Dinosauria: Sauropoda; Morrison Formation - Latest Jurassic)". PeerJ PrePrints. doi:10.7287/peerj.preprints.838v1.
  10. ^ Carpenter, Kenneth (2018-10-19). "Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado". Geology of the Intermountain West. 5: 227–244. doi:10.31711/giw.v5.pp227-244. ISSN 2380-7601.
  11. ^ Paul, Gregory S. (2019). "Determining the largest known land animal: A critical comparison of differing methods for restoring the volume and mass of extinct animals" (PDF). Annals of the Carnegie Museum. 85 (4): 335–358. doi:10.2992/007.085.0403. S2CID 210840060.
  12. ^ Bates, Karl T.; Falkingham, Peter L.; Macaulay, Sophie; Brassey, Charlotte; Maidment, Susannah C.R. (2015). "Downsizing a giant: re-evaluating Dreadnoughtus body mass". Biol Lett. 11 (6): 20150215. doi:10.1098/rsbl.2015.0215. PMC 4528471. PMID 26063751.
  13. ^ Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi:10.4202/app.00136.2014. S2CID 2092950. Archived (PDF) from the original on 2016-08-24.
  14. ^ Sander, P. Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T.; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jürgen; Mallison, Heinrich; et al. (2011). "Biology of the sauropod dinosaurs: the evolution of gigantism". Biological Reviews. 86 (1): 117–155. doi:10.1111/j.1469-185X.2010.00137.x. PMC 3045712. PMID 21251189.
  15. ^ Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus." In Foster, J.R. and Lucas, S.G., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 131–138.
  16. ^ Colbert, Edwin Harris (1971). Men and dinosaurs: the search in field and laboratory. Harmondsworth [Eng.]: Penguin. ISBN 978-0-14-021288-4.
  17. ^ Mazzetta, G.V.; et al. (2004). "Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs". Historical Biology. 16 (2–4): 1–13. CiteSeerX 10.1.1.694.1650. doi:10.1080/08912960410001715132. S2CID 56028251.
  18. ^ Janensch, W. (1950). "The Skeleton Reconstruction of Brachiosaurus brancai": 97–103. {{cite journal}}: Cite journal requires |journal= (help)
  19. ^ "The World of Dinosaurs". Museum für Naturkunde. Archived from the original on 2018-11-16. Retrieved 2018-11-16.
  20. ^ Lucas, H.; Hecket, H. (2004). "Reappraisal of Seismosaurus, a Late Jurassic Sauropod". Proceeding, Annual Meeting of the Society of Paleontology. 36 (5): 422.
  21. ^ a b c Molina-Pérez, Rubén; Larramendi, Asier (2020). Dinosaur Facts and Figures The Sauropods and Other Sauropodomorphs. Translated by Donaghey, Joan. Illustrated by Andrey Atuchin and Sante Mazzei. Princeton: Princeton University Press. ISBN 978-0-691-20297-6. OCLC 1157079384.
  22. ^ Morgan, James (2014-05-17). "'Biggest dinosaur ever' discovered". BBC News. Archived from the original on 2017-02-18. Retrieved 2017-03-21.
  23. ^ "Don't believe the hype: Patagotitan was not bigger than Argentinosaurus". Sauropod Vertebra Picture of the Week. 2017-08-09. Archived from the original on 2019-04-14. Retrieved 2019-02-19.
  24. ^ Paul, Gregory (December 2019). "Determining the Largest Known Land Animal: A Critical Comparison of Differing Methods for Restoring the Volume and Mass of Extinct Animals" (PDF). Annals of Carnegie Museum. 85 (4): 335–358. doi:10.2992/007.085.0403. ISSN 0097-4463. S2CID 210840060.
  25. ^ Patricia Vickers Rich, Thomas Hewitt Rich, Mildred Adams Fenton, Carroll Lane (January 15, 2020). The Fossil Book: A Record of Prehistoric Life. Dover Publications. p. 444. Retrieved 2022-08-25.{{cite book}}: CS1 maint: multiple names: authors list (link)
  26. ^ Lu, J., Li, T., Zhong, S., Azuma, Y., Fujita, M., Dong, Z., and Ji, Q. (2007). "New yunnanosaurid dinosaur (Dinosauria, Prosauropoda) from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan Province of China". Memoir of the Fukui Prefectural Dinosaur Museum, 6: 1-15.
  27. ^ Therrien, F.; Henderson, D. M. (2007). "My theropod is bigger than yours...or not: estimating body size from skull length in theropods". Journal of Vertebrate Paleontology. 27 (1): 108–115. doi:10.1671/0272-4634(2007)27[108:MTIBTY]2.0.CO;2. S2CID 86025320.
  28. ^ "See what African Wildlife Foundation is doing to protect these iconic flightless birds". 2013-02-25. Archived from the original on 2015-04-29. Retrieved 2015-04-18.
  29. ^ Xu, X., Zhao, Q., Norell, M., Sullivan, C., Hone, D., Erickson, G., Wang, X., Han, F. and Guo, Y. (2009). "A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin." Chinese Science Bulletin, 6 pages, accepted November 15, 2008.
  30. ^ Pascal Godefroit; Andrea Cau; Hu Dong-Yu; François Escuillié; Wu Wenhao; Gareth Dyke (2013). "A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds". Nature. 498 (7454): 359–62. Bibcode:2013Natur.498..359G. doi:10.1038/nature12168. PMID 23719374. S2CID 4364892.
  31. ^ Which was the smallest dinosaur? Archived 2011-07-06 at the Wayback Machine Royal Tyrrell Museum. Last accessed 22 September 2022.
  32. ^ Averianov AO, Lopatin AV (2022). "A re-appraisal of Parvicursor remotus from the Late Cretaceous of Mongolia: implications for the phylogeny and taxonomy of alvarezsaurid theropod dinosaurs". Journal of Systematic Palaeontology. 19 (16): 1097–1128. doi:10.1080/14772019.2021.2013965. S2CID 247222017.
  33. ^ Conservation International (Content Partner); Mark McGinley (Topic Editor). 2008. "Biological diversity in the Caribbean Islands." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth May 3, 2007; Last revised August 22, 2008; Retrieved November 9, 2009]. Archived 2013-05-23 at the Wayback Machine>
  34. ^ Borenstein, Seth (July 31, 2014). "Study traces dinosaur evolution into early birds". AP News. Archived from the original on August 8, 2014. Retrieved August 3, 2014.
  35. ^ Zoe Gough (31 July 2014). "Dinosaurs 'shrank' regularly to become birds". BBC. Archived from the original on 20 February 2015. Retrieved 20 April 2015.

External links