Data from: δ18O-derived incubation temperatures of oviraptorosaur eggs

In order to determine the incubation temperature of eggs laid by non-avian dinosaurs, we analysed the oxygen isotope compositions of both eggshell carbonate (δ18Oc) and embryo bone phosphate (δ18Op) from seven oviraptorosaur eggs with preserved in ovo embryo bones. These eggs come from the Upper Cretaceous Nanxiong Formation of Jiangxi Province, China. Oviraptorosaur theropods were selected because of their known brooding behaviour as evidenced by preserved adult specimens fossilized in brooding posture on their clutch. Incubation temperature of these embryos was estimated based on the following considerations: eggshell δ18Oc value reflects the oxygen isotope composition of egg water fluid; embryo bones precipitate from the same egg fluid; and oxygen isotope fractionation between phosphate and water is controlled by the egg temperature. A time-dependent model predicting the δ18Op evolution of the embryo skeleton during incubation as a function of egg temperature was built, and measured δ18Oc and δ18Op values used as boundary conditions. According to the model outputs, oviraptorosaurs incubated their eggs within a 35–40°C range, similar to extant birds and compatible with the known active brooding behaviour of these theropod dinosaurs. Provided that both eggshell and embryo bones preserved their original oxygen isotope compositions, this method could be extended to investigate some reproductive traits of other extinct groups of oviparous amniotes.

为测定非鸟类恐龙所产恐龙蛋的孵化温度，我们针对7枚保存有卵内胚胎骨骼的窃蛋龙类（oviraptorosaur）恐龙蛋，开展了蛋壳碳酸盐（δ¹⁸O_c）与胚胎骨磷酸盐（δ¹⁸O_p）的氧同位素组成分析。这些蛋产自中国江西省上白垩统南雄组。选择窃蛋龙类兽脚类恐龙作为研究对象，是因为其孵卵行为已有确凿证据：成年个体以孵卵姿态伏于其窝卵之上的化石标本被发现。本次研究基于以下思路估算胚胎的孵化温度：蛋壳的δ¹⁸O_c值反映了蛋内流体的氧同位素组成；胚胎骨骼沉淀自相同的蛋内流体；而磷酸盐与水之间的氧同位素分馏受孵化温度调控。我们构建了一个时间依赖模型，该模型可基于孵化温度预测孵化过程中胚胎骨骼的δ¹⁸O_p演化规律，并将实测得到的δ¹⁸O_c与δ¹⁸O_p值作为边界条件代入模型。模型结果显示，窃蛋龙类的孵化温度处于35~40℃区间，与现生鸟类的孵化温度相近，也与这类兽脚类恐龙已知的主动孵卵行为相符。若蛋壳与胚胎骨骼均保留了原始的氧同位素组成，该方法可推广应用于探究其他已灭绝卵生羊膜类类群的部分繁殖性状。