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What are the current and up-to-date estimates of the size of the big sauropod dinosaur Apatosaurus (the biggest species of it) in terms of mass range (weight) and total length? I prefer the answer in metric units.

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From the wikipedia page on Apatosaurus:

Most size estimates are based on specimen CM 3018, the type specimen of A. louisae. In 1936 this was measured to be 21.8 m (72 ft), by measuring the vertebral column.[5]

Current estimates are similar, finding that the individual was 21–22.8 m (69–75 ft) long and had a mass of 16.4–22.4 t (16.1–22.0 long tons; 18.1–24.7 short tons).[6][7][8]

A 2015 study that estimated the mass of volumetric models of Dreadnoughtus, Apatosaurus, and Giraffatitan estimates CM 3018 at 21.8–38.2 t (21.5–37.6 long tons; 24.0–42.1 short tons), similar in mass to Dreadnoughtus.[9]

Past estimates have put the creature's mass as high as 35.0 t (34.4 long tons; 38.6 short tons).[6]

Some specimens of A. ajax (such as OMNH 1670) represent individuals 11–30% longer, suggesting masses twice that of CM 3018 or 32.7–72.6 t (32.2–71.5 long tons; 36.0–80.0 short tons), potentially rivalling the largest titanosaurs.[10]


  1. "Osteology of Apatosaurus, with special references to specimens in the Carnegie Museum". Memoirs of the Carnegie Museum. 11 (4): 1–136, Gilmore, C.W. (1936).
  2. "A new method to calculate allometric length-mass relationships of dinosaurs". Journal of Vertebrate Paleontology. 21 (1): 51–52, Seebacher, F. (2001).
  3. "Giants and bizarres: body size of some southern South American Cretaceous dinosaurs" Historical Biology. 16 (2–4): 71–83, Mazzetta, G.V.; Christiansen, P.; Farina, R.A. (2004).
  4. "Burly Gaits: Centers of mass, stability, and the trackways of sauropod dinosaurs". Journal of Vertebrate Paleontology. 26 (4): 907–921, Henderson, D.M. (2006).
  5. "Downsizing a giant: re-evaluating Dreadnoughtus body mass". Biology Letters. 11 (6), Bates, K.T.; Falkingham, P.L.; Macaulay, S.; Brassey, C.; Maidment, S.C.R. (2015).
  6. "A giant, skeletally immature individual of Apatosaurus from the Morrison Formation of Oklahoma" 61st Symposium on Vertebrate Palaeontology and Comparative Anatomy - Programme and Abstracts: 40–45, Wedel, M. (2013).

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  • $\begingroup$ So if I understand correctly, the largest Apatosaurus was about 26-27 meters long and may have weighed 50+ metric tons. $\endgroup$ – Dr. Evenor Jul 1 '18 at 7:04

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