The mascot of the 2023 Spring Festival Gala of the China Central Radio and Television Station, the image of Rabbit Yuanyuan with fluffy and plush shape, lively and healing attitude, and large, layered eyes, is taken from the fossil Mimotona wana (about 60-62 million years old) found by scientists from the Institute of Vertebrate and Paleoanthropology of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Vertebrate Paleontology) in the southern part of Tianzhushan UNESCO Global Geopark. The fossil Mimotona wana is an ancestral species of Lagomorpha and suggests an important clue to a classic scientific question in the study of Lagomorpha over the past 300 years.

I. The characteristics of rabbits

Whenever we see rabbits, they always look busy and they are constantly chewing their food all the time. This is because a rabbit's incisors grow constantly. If they cannot grind their teeth sufficiently, the incisors will grow outwards rapidly and the overgrown incisors will prevent the rabbit's lips from closing and prevent them from eating properly, which can lead to death in serious cases. For rabbits, they are grinding their teeth with their lives. And for scientists, the pair of incisors is also quite important, a feature that distinguishes rabbits from other mammals. However, among mammals with large incisors that grow throughout their lives, apart from rabbits there are also rats, so rabbits and rats have always been thought to be closely related.

As early as 1735, the biologist Linnaeus, the founder of modern taxonomy, included rabbits and rats together as rodents. It was not until 200 years later that scientists began to point out the differences in the morphology of the incisors of rabbits and rats, and that the Lagomorpha had a pair of small incisors hidden near the large incisors in the upper jaw, which were clearly more complex than those of rodents. Not only that, more and more scholars searched for more differences between the two, turning to the suggestion that rabbits and rats are not related to each other. This debate, which lasted nearly 100 years, led to one of the classic scientific questions in the history of rabbit studies: where in the evolutionary history of life does the rabbit fit into the great mammalian tree? The only way to find out how the rabbit originated and whether it is related to rodents is to look for clues in fossils.

II. The origin of rabbits

In order to solve this centuries-old puzzle, paleontological predecessors have visited many fossil strata around the world. Since the 1960s, the Chinese Academy of Sciences (CAS) have organized a large-scale expedition to the "Red Formation" in southern China and discovered a mammalian fauna unique to Asia in the Paleocene strata, which provided an opportunity to explore the origins of rodents and rabbits. In the 1970s, a field team from the Institute of Vertebrate Paleontology discovered two important fossil skulls with large incisors (Early Paleocene, about 60-62 million years ago) in Qianshan, Anhui Province (the site of Tianzhushan UGGp). After research by Mr. Li Chuankui, a paleomammalogist and researcher of the Institute of Vertebrate Paleontology in China, the fossils were named Mimotona wana and Heomys orientalis, which are respectively the ancestral species of Lagomorpha and the ancestral species of rodents, and they are proven to be of the same origin.

The mascot Rabbit Yuanyuan not only embodies the meaning and beauty of the traditional Chinese zodiac sign of the rabbit, but also shines a light on the outstanding scientific achievements and the tenacity of Chinese scientists.