Early Cretaceous Keteleerioxylon Wood in the Songliao Basin, Northeast China, and Its Geographic and Environmental Implications

SIMPLE SUMMARY: Keteleeria is a small group of Pinaceae, now only distributed in east and southeast Asia, but which was widely distributed in Asia, Europe, and North America in the northern hemisphere during the Late Mesozoic and Cenozoic periods. A new Keteleeria-like wood fossil, Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov., was described in the Early Cretaceous strata about 110 million years ago in Changchun, Jilin Province, Northeast China. The growth rings of wood contain rich palaeoecological and paleoclimatic information. Quantitative analysis of growth rings revealed that the new species is evergreen with leaf longevity of 1–3 years. The growth rings of Keteleerioxylon changchunense indicate that the climate seasonality was pronounced in the Songliao Basin during the Early Cretaceous period. By reviewing Keteleeria and closely related fossil taxa, we depict the probable migration route of Keteleeria. The oldest Keteleeria-like wood was found in the middle Jurassic period in Svalbard, Norway. They were distributed in both the middle and the high latitudes during the Late Jurassic–Cretaceous global warming time, while during the Paleogene and Neogene cooling times, the Keteleeria-like wood became scarce, especially in the Quaternary Glaciation, and until now, they were strictly restricted to the subtropical and tropical regions of east and southeast Asia. ABSTRACT: The extant Keteleeria is endemic to east and southeast Asia, while Keteleeria-like trees were widely distributed in the northern hemisphere in Earth’s history. In this paper, we reported a novel wood fossil of Keteleerioxylon changchunense Shi, Sun, Meng et Yu sp. nov., collected from the middle part of the Yingcheng Formation, Yingcheng Coal Mine, Changchun City, Jilin Province, northeast China. The quantitative growth-ring analyses of K. changchunense indicate that it was evergreen with a leaf longevity of 1–3 years, which is consistent with the foliar retention of extant Keteleeria. Its high ring-markedness index (RMI) indicates that the climate seasonality was pronounced during the Early Albian period in the Songliao Basin, northeast China. The fossil records of Keteleeria and closely related taxa indicate that this group might have originated from high latitudes in the northern hemisphere, then spread and migrated southward during the Late Jurassic and Cretaceous periods, gradually decreased in the Cenozoic period, and so far only survives in east and southeast Asia.