Data from: Diets of giants: the nutritional value of sauropod diet during the Mesozoic

A major uncertainty in estimating energy budgets and population densities of extinct animals is the carrying capacity of their ecosystems, constrained by net primary productivity (NPP) and its digestible energy content. The hypothesis that increases in NPP due to elevated atmospheric CO2 contributed to the unparalleled size of the sauropods has recently been rejected, based on modern studies on herbivorous insects that imply a general, negative correlation of diet quality and increasing CO2. However, the nutritional value of plants grown under elevated CO2 levels might be very different for vertebrate megaherbivores than for insects. Here we show plant species‐specific responses in metabolizable energy and nitrogen content, equivalent to a two‐fold variation in daily food intake estimates for a typical sauropod, for dinosaur food plant analogues grown under CO2 concentrations spanning estimates for Mesozoic atmospheric concentrations. Our results potentially rebut the hypothesis that constraints on sauropod diet quality were driven by Mesozoic CO2 concentration.在估算已灭绝动物的能量收支与种群密度的过程中，一项核心不确定性在于其生态系统的环境容纳量（carrying capacity），而该容纳量受净初级生产力（net primary productivity, NPP）及其可消化能含量的约束。此前有假说提出，大气二氧化碳浓度升高所提升的净初级生产力，推动了蜥脚类恐龙演化出空前庞大的体型，但该假说近期已被驳斥，其依据是针对植食性昆虫的现代研究——这类研究表明食物质量与二氧化碳浓度升高普遍呈负相关关系。然而，对于脊椎动物巨型植食动物而言，高二氧化碳浓度环境下生长的植物，其营养价值可能与昆虫存在显著差异。本研究针对覆盖中生代大气二氧化碳浓度估算范围的梯度条件下种植的恐龙食性植物类似物展开分析，结果显示不同植物物种的代谢能与氮含量存在物种特异性响应，其差异幅度相当于典型蜥脚类恐龙每日摄食量估算值出现两倍级别的波动。本研究结果或可驳斥"中生代二氧化碳浓度驱动了蜥脚类恐龙食物质量限制"这一假说。