It is a land giant, but it eats with its nose! The reason is a catalyst from millions of years ago!

Elephants are the largest terrestrial mammals, and their soft and flexible trunks are particularly eye-catching. Previous studies have shown that early elephants not only had long trunks, but also long jaws. However, the long jaws of elephants later unexpectedly shortened. What is the internal mechanism of this legendary evolutionary process? How do elephants with long trunks and long jaws eat? Paleontologists have not been able to give a reasonable explanation for these questions.

Source: Tuchong Creative

Researchers from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences and other institutions conducted an in-depth study of the jaws and trunks of early elephants, revealing the feeding methods of early elephants and the unique evolution of related organs. The relevant research results were published online in the international academic journal "eLife" on November 28.

Research shows that as early as the Middle Miocene climatic optimum period 17 to 15 million years ago, the star species among early elephants, the shovel-toothed elephant with a shovel-shaped jaw, had developed a way of eating by using its trunk to wrap around plants and its jaw to cut off the plants. This is the earliest evidence that the elephant trunk could achieve the wrapping function.

At the same time, the research team also conducted a comparative study on the functional morphology of three major types of long-jawed mastodons: shovel-toothed elephants, gomphotheres and hog-toothed elephants. The results showed that shovel-toothed elephants, gomphotheres and gomphotheres had different feeding methods and living environments.

The Shoveltooth lived in a relatively open environment, and its lower jaw was only suitable for cutting vertically growing plants. It used its flexible trunk to hold the plants and then used its lower jaw to cut horizontally. This way of feeding was very efficient; the Hogwarts lived in a relatively closed environment, and its lower jaw was suitable for cutting horizontally or inclined growing branches. It used its trunk to help press down the branches and then cooperated with its lower jaw to complete the feeding; the Gomphotherium's living environment was between the two or overlapped with both. Its feeding methods were diverse, and it had good adaptability in both woodlands and grasslands.

"We found that the elongated lower jaw and lower incisors were the main feeding organs of early elephants, while the trunk was only an auxiliary tool. Early elephants with different lower jaw morphologies had different ecological adaptabilities." Wang Shiqi, co-corresponding author of the paper and researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, said that as the ecological environment gradually became dry and cold, the shovel-toothed elephant was better able to adapt to the relatively open ecological environment. It fed on herbaceous plants, which ultimately promoted the development of the grasping function and flexibility of the trunk.

"The adaptability of feeding behavior in open environments is the catalyst for the evolution of the grasping function of the trunk. In an open ecological environment, the feeding function of elephants is completely transferred to the long trunk, which eventually leads to the shortening of the original feeding organs - the lower jaw and lower incisors." Wang Shiqi further explained.

The editor of eLife magazine gave a high evaluation of this achievement: "This study combines multiple cutting-edge methods and provides very convincing results in many aspects such as ecomorphology, behavioral ecology and co-evolutionary biology." The reviewers also highly praised this work: "This study has sufficient evidence, beautiful illustrations, sufficient and detailed supplementary file data, and detailed and easy-to-understand three-dimensional models and animated videos. This is of great significance for understanding the diversity of proboscideans and the co-evolution of feeding organs, and also provides a solid foundation for further exploration of life sciences and evolutionary biology."

Deng Tao, co-corresponding author of the paper and researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, said that this study provides important evidence for understanding the evolution and ecological background of the trunk and mandible of this important group of elephants, and provides new insights into how proboscideans adapt to the environment and how environmental changes shape the evolution of unique organs.