Biology and Geology Departments, Macalester College, St. Paul, MN 55105, USA.
Department of Biology, University of Washington, Seattle, WA 98185-1800, USA.
Science. 2016 Apr 22;352(6284):450-3. doi: 10.1126/science.aaf1509. Epub 2016 Apr 21.
Sauropod dinosaurs exhibit the largest ontogenetic size range among terrestrial vertebrates, but a dearth of very young individuals has hindered understanding of the beginning of their growth trajectory. A new specimen of Rapetosaurus krausei sheds light on early life in the smallest stage of one of the largest dinosaurs. Bones record rapid growth rates and hatching lines, indicating that this individual weighed ~3.4 kilograms at hatching. Just several weeks later, when it likely succumbed to starvation in a drought-stressed ecosystem, it had reached a mass of ~40 kilograms and was ~35 centimeters tall at the hip. Unexpectedly, Rapetosaurus limb bones grew isometrically throughout their development. Cortical remodeling, limb isometry, and thin calcified hypertrophic metaphyseal cartilages indicate an active, precocial growth strategy.
蜥脚类恐龙在陆地脊椎动物中表现出最大的个体发育体型范围，但由于缺乏非常年幼的个体，因此人们对它们生长轨迹的起点了解甚少。雷托龙的一个新标本揭示了最大恐龙中最小阶段的早期生活。骨骼记录了快速的生长速度和孵化线，表明该个体在孵化时的体重约为 3.4 公斤。仅仅几周后，当它可能在一个干旱压力的生态系统中因饥饿而死亡时，它的体重已经达到了约 40 公斤，臀部高度约为 35 厘米。出乎意料的是，雷托龙的四肢骨骼在整个发育过程中都是等长生长的。皮质重塑、肢体等长和薄的钙化肥大骺软骨表明了一种活跃的、早熟的生长策略。
