Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi Zhi Men Wai DaJie, Beijing 100044, China.
Proc Natl Acad Sci U S A. 2011 Mar 29;108(13):5179-83. doi: 10.1073/pnas.1011369108. Epub 2011 Mar 10.
Early Cretaceous vertebrate assemblages from East Asia and particularly the Jehol Biota of northeastern China flourished during a period of highly debated climatic history. While the unique characters of these continental faunas have been the subject of various speculations about their biogeographic history, little attention has been paid to their possible climatic causes. Here we address this question using the oxygen isotope composition of apatite phosphate (δ ) from various reptile remains recovered from China, Thailand, and Japan. δ values indicate that cold terrestrial climates prevailed at least in this part of Asia during the Barremian-early Albian interval. Estimated mean air temperatures of about 10 ± 4 °C at midlatitudes (∼ 42 °N) correspond to present day cool temperate climatic conditions. Such low temperatures are in agreement with previous reports of cold marine temperatures during this part of the Early Cretaceous, as well as with the widespread occurrence of the temperate fossil wood genus Xenoxylon and the absence of thermophilic reptiles such as crocodilians in northeastern China. The unique character of the Jehol Biota is thus not only the result of its evolutionary and biogeographical history but is also due to rather cold local climatic conditions linked to the paleolatitudinal position of northeastern China and global icehouse climates that prevailed during this part of the Early Cretaceous.
早白垩世东亚的脊椎动物组合，特别是中国东北地区的热河生物群，在一段极具争议的气候历史时期中繁盛。尽管这些大陆动物群的独特特征一直是关于其生物地理历史的各种推测的主题，但很少有人关注它们可能的气候原因。在这里，我们使用从中国、泰国和日本采集的各种爬行动物遗骸中的磷灰石磷酸盐的氧同位素组成来解决这个问题（δ）。δ 值表明，在巴雷姆期到早阿尔比期之间，至少在亚洲的这一地区，寒冷的陆地气候盛行。中纬度（约 42°N）地区约 10 ± 4°C 的估计平均气温与当今凉爽的温带气候条件相对应。如此低的温度与之前报道的该早白垩世时期海洋温度较低的情况一致，也与温带化石木属 Xenoxylon 的广泛存在以及中国东北地区缺乏喜热爬行动物（如鳄鱼）的情况一致。因此，热河生物群的独特性不仅是其进化和生物地理历史的结果，还与中国东北地区的古纬度位置以及早白垩世时期盛行的全球冰室气候相关的当地较冷气候条件有关。
