Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
Sci Adv. 2020 Feb 14;6(7):eaax9361. doi: 10.1126/sciadv.aax9361. eCollection 2020 Feb.
Studying the origin of avian thermoregulation is complicated by a lack of reliable methods for measuring body temperatures in extinct dinosaurs. Evidence from bone histology and stableisotopes often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δO) of body water. Clumped isotope (Δ) paleothermometry, based on binding of C to O, provides a more robust tool, but has yet to be applied across a broad phylogenetic range of dinosaurs while accounting for paleoenvironmental conditions. Applying this method to well-preserved fossil eggshells demonstrates that the three major clades of dinosaurs, Ornithischia, Sauropodomorpha, and Theropoda, were characterized by warm body temperatures. Dwarf titanosaurs may have exhibited similar body temperatures to larger sauropods, although this conclusion isprovisional, given current uncertainties in taxonomic assignment of dwarf titanosaur eggshell. Our results nevertheless reveal that metabolically controlled thermoregulation was the ancestral condition for Dinosauria.
研究鸟类体温调节的起源很复杂，因为缺乏可靠的方法来测量已灭绝恐龙的体温。骨组织学和稳定同位素的证据通常依赖于对生长速度与体温之间关系或体水同位素组成（δO）的不确定假设。基于 C 与 O 结合的聚类同位素（Δ）古体温计量法提供了一种更可靠的工具，但在考虑古环境条件的情况下，仍有待在恐龙的广泛系统发育范围内应用。将这种方法应用于保存完好的化石蛋壳表明，恐龙的三个主要分支，鸟臀目、蜥脚形亚目和兽脚亚目，其体温较高。矮泰坦巨龙的体温可能与较大的蜥脚类恐龙相似，尽管这一结论是暂定的，因为目前在矮泰坦巨龙蛋壳的分类学归属上存在不确定性。然而，我们的研究结果揭示了代谢控制的体温调节是恐龙的原始状态。
