Abstract 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 CO 2 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 CO 2. However, the nutritional value of plants grown under elevated CO 2 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 CO 2 concentrations spanning estimates for Mesozoic atmospheric concentrations. Our results potentially rebut the hypothesis that constraints on sauropod diet quality were driven by Mesozoic CO 2 concentration.

中文翻译：

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巨人的饮食：中生代蜥脚类动物饮食的营养价值

摘要 估计已灭绝动物的能量预算和种群密度的一个主要不确定性是其生态系统的承载能力，受到净初级生产力（NPP）及其可消化能量含量的限制。基于对草食性昆虫的现代研究，由于大气中 CO 2 升高导致 NPP 增加导致蜥脚类动物无与伦比的体型，这一假设最近已被驳回，该研究表明饮食质量与 CO 2 增加之间存在普遍的负相关关系。在高 CO 2 水平下生长的植物的营养价值对于脊椎动物大型食草动物来说可能与昆虫有很大不同。在这里，我们展示了植物物种在可代谢能量和氮含量方面的特定反应，相当于典型蜥脚类恐龙每日食物摄入量估计值的两倍变化，对于在 CO 2 浓度范围内生长的恐龙食用植物类似物来说，其浓度跨越了中生代大气浓度的估计值。我们的结果可能反驳这样的假设：蜥脚类动物饮食质量的限制是由中生代CO 2 浓度驱动的。