Saber-toothed elephants are an extinct genus of the subfamily Saber-toothed elephants of the family Euphalidae proboscis, most prosperous in the Pliocene and Pleistocene continents of Asia. The earliest saber-toothed elephants appeared in the Late Miocene and could survive until the Late Pleistocene at the latest. There are currently two views on the origin of the saber-toothed elephant: the conventional view is that the saber-toothed elephant originated in Asia, while the other view is that it originated in Africa. At present, there are two sites in Gansu Lanzhou Basin and Shanxi Yushe Basin produced late Miocene saber-tooth elephant fossils, of which the Yushe Basin saber-tooth elephant fossils are determined to be about 6 million years old through magnetic stratigraphy, while the saber-toothed elephant fossil age in Lanzhou Basin is currently only constrained by the biological stratigraphy of the associated mammal group, that is, it is only known that it is located in the Late Miocene, and it lacks more accurate dating. On the other hand, the oldest saber-toothed elephant fossil found in Kenya, Africa, is about 7 million years old, about 1 million years earlier than the saber-toothed elephant fossil in China's Yushe Basin, which provides evidence for the origin of saber-toothed elephants in Africa. Therefore, the exact dating of the saber-tooth elephant fossils in the Lanzhou Basin is crucial to revealing the origin of the saber-toothed elephant.
Ao Hong, a researcher at the Institute of Earth Environment of the Chinese Academy of Sciences, and his colleagues inside and outside the United Nations, with the joint support of the National Key Basic Research and Development Program ("973") project and the National Natural Science Foundation of China, carried out a detailed magnetic stratigraphic study of the Xingjiawan section containing saber-toothed elephant fossils in the Lanzhou Basin. The results show that there are two comparison schemes between the established xingjiawan profile magnetic stratigraphic sequence and the standard polarity chronology of the Late Miocene (Figure 1). A comparative scheme showed that the Xingjiawan profile recorded the polarity band from C5r.2n to C4n.1n, and the profile age was about 11.6–7.6 Ma. The Xingjiawan fauna is located near the boundary of the C5r.1r and C5n.2n polar bands and is about 11 Ma in age. Another contrast scheme showed that the Xingjiawan profile recorded polarity bands from C4An.2n to C3n.2n, with a profile age of about 8.9–4.8 Ma. The Xingjiawan fauna is located near the boundary of the C4r.1r and C4n.2n polar bands, and its age is about 8 Ma.
This study shows that the fossil saber-toothed elephant contained in the Xingjiawan fauna is at least 8 million years old, and may reach 11 million years, both of which are earlier than the era of African saber-toothed elephants, and are currently the earliest saber-toothed elephant fossils in the world. Therefore, this provides new chronological evidence for the traditional view of the origin of the saber-toothed elephant in Asia, and the saber-toothed elephant should have come out of the Lanzhou Basin of China and gradually migrated to Africa (Figure 2). In addition, there are both forest-type and grassland-type species among the mammals of the Xingjiawan Fauna, which indicates that the Lanzhou Basin has a mix of forest and grassland vegetation types in the Late Miocene, which is significantly different from the current arid-semi-arid grassland vegetation types.
The findings were published in the international geological journal Earth and Planetary Science Letters. New magnetochronology of Late Miocene mammal fauna, NE Tibetan Plateau, China: mammal migration and paleoenvironments. Earth and Planetary Science Letters, 2016, 434, 220–230)。