An elephant skull fossil, dating back to six million years, was discovered in Shuitangba in Zhaotong City in China. The recent discovery suggests the species originated somewhere in the Yunnan province or in nearby areas.

Prior to the skull discovery, the earliest known fossil of the mastodon species was found in Shanxi Province located in northwest China. According to vertebrate evolution expert Wang Shiqi from the Chinese Academy of Sciences, the recent discovery pushed back the species' history by one million years.

"The origin of the Old World brevirostrine gomphotheriid taxon sinomastodon has been debated intensively. The discovery of the oldest known sinomastodon cranium, reported herein, supports its endemic origin and contradicts the prevalent theory of its North America origin," wrote the researchers in the study published in the November edition of Journal of Mammalian Evolution.

The newly discovered fossil was named Sinomastodon praeintermedius, which showed diverse features from other Sinomastodon species. Researchers found that the fossil of the elephant skull was tough enough to survive possible head-to-head collisions. The back part of the skull was flat and had spread-out arches that protected the brain in all corners. The skull also bore air cavities which helped lower the overall weight.

The sinomastodon, also called "Chinese mastodont" is an extinct species of the gomphothere genus (Proboscidea order) who are the ancient relatives of modern-day elephants. The species can be traced back to the late Miocene to the early Pleistocene period in south-east Asia, primarily in Indonesia, Japan and China. The species is commonly mistaken for another extinct mammal species, the Mammut which belongs to a different family in the Proboscidea order.

The discovery was carried out by collaborating archaeologists from the Chinese Academy of Sciences (CAS) and Pennsylvania State University.