linguistic:translation
Growth

A 1999 microscopic study of Apatosaurus and Brontosaurus bones concluded the animals grew rapidly when young and reached near-adult sizes in about 10 years. In 2008, a study on the growth rates of sauropods was published by Thomas Lehman and Holly Woodward. They said that by using growth lines and length-to-mass ratios, Apatosaurus would have grown to 25 t (25 long tons; 28 short tons) in 15 years, with growth peaking at 5,000 kg (11,000 lb) in a single year. An alternative method, using limb length and body mass, found Apatosaurus grew 520 kg (1,150 lb) per year, and reached its full mass before it was about 70 years old. These estimates have been called unreliable because the calculation methods are not sound; old growth lines would have been obliterated by bone remodeling. One of the first identified growth factors of Apatosaurus was the number of sacral vertebrae, which increased to five by the time of the creature's maturity. This was first noted in 1903 and again in 1936.

Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Eva Griebeler et al. (2013) examined long-bone histological data and concluded the Apatosaurus sp. SMA 0014 weighed 20,206 kg (22.3 short tons), reached sexual maturity at 21 years, and died aged 28. The same growth model indicated Apatosaurus sp. BYU 601–17328 weighed 18,178 kg (20.0 short tons), reached sexual maturity at 19 years, and died aged 31.