"Mummy" plant? Let's see the 15 million-year-old Chinese jujube!

Author: Liu Yun, Wang Zixi, Tan Chao, Wang Guanqun, Pan Haochen (Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences)

The article comes from the Science Academy official account (ID: kexuedayuan)

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The famous "mummy" is a way for ancient people to preserve corpses, and "dehydration" is a key step in the production process.

(Photo source: veer photo gallery)

The ancient Egyptians used mummification to preserve many human and animal bodies. Recently, scientists discovered 15 million-year-old South Jujube fossils in Fujian. The formation process of these South Jujube fossils is like a "mummy" made by nature...

First of all, what is southern jujube?

When it comes to jujube, everyone is familiar with it. In autumn and winter, small round jujubes hang on the branches. If you hit them with a pole, the small jujubes will fall like hail.

There are differences between the jujubes in the south and north. The southern sour jujube (also known as the five-eyed fruit) is a unique jujube in the south. Strictly speaking, it is not the fruit of the jujube tree, but the fruit of a lacquer tree, which is a distant relative of the mango. It is mainly distributed in Zhejiang, Fujian, Hubei, Hunan, Guangdong, Guangxi, Yunnan, Guizhou and other places in my country.

Choerospondias australis (Source: Sohu)

The fruit of the Chinese jujube is composed of a thin pericarp, a woody endocarp, an edible mesocarp and a pulp. In addition to being eaten, there is another interesting thing about the Chinese jujube. It is not easy to see the complete fruit, but if you eat the pulp completely, you can find that there are often five neatly arranged small holes on the top of its core, so it is also called the "five-eyed fruit", which means "five blessings come to the door". The magical thing is that each small hole can grow a bud, and a seed in the core can grow into five seedlings, so the Chinese jujube also has the Zen meaning of "one flower blooms five leaves".

Living South Ziziphus spinulosa kernel (Image source: Baidu Gallery)

Jujube axillaris fossils: a “mummy”-like preservation method

When did the Chinese wolfberry appear?

According to archaeological evidence, ancient people began eating Chinese jujube more than 8,000 years ago and liked to store its fruits in large quantities.

Recently, researchers from the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, and their counterparts from the Chicago Botanic Garden in the United States discovered 15 million-year-old Chinese jujube fossils in the Miocene Fotan flora in Zhangpu, Fujian. Unlike traditional preservation methods, these Chinese jujube fossils are like "mummies", preserving the ancient Chinese jujube's morphological structure in a three-dimensional manner through drying and dehydration. There are 7 Chinese jujube fruit fossils collected this time, and through the "mummy"-style preservation, not only their appearance is preserved intact, but also the seeds inside these fruits are well preserved.

Existing southern jujube (Source: Sohu-Photography Travel Notes)

Macroscopic morphology (1-3) and microstructural characteristics (4-6) of the fruit fossil of Choerospondias australis (Source: Nanjing Institute of Paleontology)

Researchers found that this batch of Choerospondias fruit fossils were very peculiar, and conducted a systematic study using experimental methods such as micro-computed tomography (Micro-CT) scanning and embedded sections. Later, the international paleobotany professional journal "Review of Palaeobotany and Palynology" reported a research result. The study found that the morphological characteristics of these 15 million-year-old Choerospondias were more diverse than those of modern ones, and they actually had seven small holes. This is also the world's first Choerospondias fruit fossil with seven germination holes, and it was named Choerospondias fujianensis sp. nov.

Micro-CT scanning of the macroscopic morphology (1-3) and internal structural characteristics (4-9) of the fruit fossil of Choerospondias australis (Source: Nanjing Institute of Paleontology)

Choerospondias australis

There is only one species of the genus Axillaris, which is endemic to East Asia. About 20 million years ago, the genus Axillaris was widely distributed in Eurasia. 15 million years ago, due to a sudden climate change, the genus disappeared in Europe and America, and only one species of Axillaris remains in East Asia. According to paleobotany and environmental archaeology data, the genus Axillaris has almost preserved continuous records in East Asia since the Oligocene. Paleoecological analysis shows that the ecological adaptation range of the genus Axillaris is relatively wide, and this feature is likely to be an important reason why the genus has continued to exist in East Asia to this day.

The research on the fossils of the southern jujube in Fujian shows that the southern jujube disappeared in Europe a long time ago, but in southern my country, they are likely to have survived from ancient times to the present day. Therefore, the environment has an important impact on the morphology of species, and species will also change some of their attributes to adapt to the environment. This is not natural selection, nor is it the survival of the fittest, but it may be born in response to the situation and change in time.

References:

[1] Zixi Wang, Fabiany Herrera, Junwu Shu, Suxin Yin, Gongle Shi*, 2020. A new Choerospondias (Anacardiaceae) endocarp from the middle Miocene of Southeast China and its paleoecological implications. Rewiew of Palaeobotany and Palynology, 283: 1–10. https://doi.org/10.1016/j.revpalbo.2020.104312.