Modeling growth rates for sauropod dinosaurs
Modeling growth rates for sauropod dinosaurs
复制标题
蜥脚类恐龙的生长速度建模
作者：
T. Lehman;H. Woodward
蜥脚类恐龙是最大的陆生动物，它们的生长速度一直是争论的主题。通过计算组织学切片上的生长线，并将骨长与体重联系起来，估计龙在短短15年的时间里达到了大约25,000公斤的成年体重，最大增长率超过5000公斤/年。这一速度超过了预估体重相当的早熟鸟类或真兽哺乳动物的速度。另一种方法是估计每条生长线的肢体长度和体重，并将所得的年龄/质量数据拟合到von Bertalanffy生长方程，得出一个修正的生长曲线，表明不解龙的成年体重是在70岁时达到的，最大增长率为520公斤/年。这种生长速度测定的替代方法也可以应用于其他蜥脚类动物的组织学研究。Janenschia的体重只有迷惑龙的一半，它花了20到30年的时间才达到成年时的体型（超过14000公斤）。这一结果得到了独立证据的支持。尽管成年后的体重比迷惑龙还大，但泰坦龙阿拉莫龙在45年内的体重达到了32000公斤，最大增长率为每年1000公斤。泰坦龙可能是所有蜥脚类动物中生长最快的。即便如此，用von Bertalanffy方程估算出的蜥脚类动物的生长速度，在估算体重相同的情况下，仍落在爬行动物和早熟鸟类之间。这些结果与小型恐龙的结果相当，表明尽管蜥脚类恐龙体型巨大，但它们的生长速度与其他恐龙相似。
Abstract Sauropod dinosaurs were the largest terrestrial animals and their growth rates remain a subject of debate. By counting growth lines in histologic sections and relating bone length to body mass, it has been estimated that Apatosaurus attained its adult body mass of about 25,000 kg in as little as 15 years, with a maximum growth rate over 5000 kg/yr. This rate exceeds that projected for a precocial bird or eutherian mammal of comparable estimated body mass. An alternative method of estimating limb length and body mass for each growth line, and fitting the resulting age/ mass data to the von Bertalanffy growth equation, yields a revised growth curve suggesting that Apatosaurus adult mass was reached by 70 years with a maximum growth rate of 520 kg/yr. This alternative method for growth rate determination can also be applied to histological studies of other sauropods. At only about half the mass of Apatosaurus, Janenschia took between 20 and 30 years to attain its adult size (over 14,000 kg). This result is supported by independent evidence of estimated bone apposition rates. Despite having an adult body mass greater than Apatosaurus, the titanosaurid Alamosaurus attained a mass over 32,000 kg within 45 years and a maximum growth rate of 1000 kg/yr. Titanosaurids may have been the fastest growing of all sauropods. Even so, sauropod growth rate estimates produced using the von Bertalanffy equation fall between those projected for reptiles and those for precocial birds of equivalent projected body mass. These results are comparable to those found for smaller dinosaurs, and suggest that sauropods grew at rates similar to other dinosaurs in spite of their great size.