The Middle Miocene mammal fossils were first recorded in literature in 1966, and listed in the regional stratigraphic table of northwest China (Gansu) (1980). At that time, when the first regional geological survey team of Gansu Geological Bureau conducted a geological survey in Linxia Basin, a batch of fossils were found in the middle and upper member of Xianshuihe Formation in Yangdujia Village, Hezheng County, and were later identified as shovel-toothed elephants, Anqima, pointed-toothed pigs and so on by relevant personnel of vertebrate paleontology Institute of Paleoanthropology, Chinese Academy of Sciences. Since then, many materials have been discovered, which were collected from Guanghe, Zhenghe and Dongxiang. Especially since 1980s, many scientific research institutions and museums have come to work in Linxia Basin and collected a large number of fossil specimens, which shows that Linxia is one of the regions with the most Miocene fossils in China.
The list of fossils is as follows (only the genus or species are described): jumping rabbit, little jumping rabbit, beaver, Gobi dog, half bear, fake cat, tooth-embedded elephant, sawtooth elephant, concentric shovel elephant, Griya shovel elephant, Anqima, claw animal, chalk-toothed rhinoceros, Spanish rhinoceros, pointed-toothed pig, Mid-Autumn Festival tusk pig, Lantian Kuban pig, ancient deer and horn pig.
As can be seen from the mammal fossils listed above, due to the existence of typical stone horses, their age belongs to the middle Miocene. From the whole fossil list, it can be seen that elephants, rhinoceroses and pigs are the main species, especially shovel-toothed elephants, and occasionally incisors and sawtooth elephants. Linxia toothless pigs are more advanced than their counterparts in the prosperous times, such as skulls and teeth. Although there is a lot of information, it is not much different from other areas in China, such as Tongxin in Ningxia, Lantian in Shaanxi, Tongur in Inner Mongolia and Kyrgyzstan in the former Soviet Union. But the age can be determined, that is, it is equivalent to the Tongur period in the late Middle Miocene, and it should be divided into the Astala period compared with Europe. According to the study of Tongxin Miocene shovel in Ningxia by Ye Jie and Jia Hang in 1986, it is considered that there are six obvious differences between Tongxin shovel and Ge Shi shovel, and it is concluded that the characteristics of concentric species are primitive, and the former is lower than the latter.
These two kinds of shovel-tooth elephants have also been found in Linxia basin, but from the discovery strata, they are basically in the same horizon, with occasional differences, but they are not very big. The distance between the upper and lower parts is in the range of 1-2 meters, and we often regard them as the same horizon. Because fossil materials mostly come from deep holes dug by farmers, and there are many stratigraphic phase changes during this period, it is difficult to judge the subtle changes between strata, or it may be the relationship between the upper and lower layers, which needs to be confirmed later.
The shovel tooth elephant found in Linxia and other places is a specialized type of elephant. The lower incisors of the shovel-tooth elephant become short and wide, and are connected with the extremely long barrel-shaped mandible to form a shovel, hence the name shovel-tooth elephant. It relies on this huge bucket to dig plants in the swamp, without a big nose as flexible as modern people.
The discovery of a very rare shovel-tooth elephant brain fossil has attracted the attention of paleontologists in China. This brain fossil was found in the pelvis by technicians of Tianjin Natural Museum while repairing the shovel-tooth elephant fossils collected from Hezheng County, Gansu Province. After taking it out, it was found to be a complete elephant brain fossil. The initial stage of brainization may be that the remains of animals are carried and impacted by water, rolling down from the skull to the pelvis, where they are buried together.