Chinese plant “Pompeii” surprises “left-handed”

Two years ago in November, Zhou Weiming and his collaborators brought back a collection of plant fossil specimens from the Uda coalfield in Inner Mongolia, where the minimum temperature was minus 20 degrees Celsius. Zhou Weiming, who works at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, did not realize that the specimen contained two palm-sized fossils, the oldest entangled plant fossilevered fossils ever found by humans, from 300 million years ago.

A entangled fossil specimen collected by Zhou Weiming from the Uda coalfield in Wuhai City, Inner Mongolia. Figure A is the first fossil, figure H is the second fossil. Photo: Current Biology

This means that since then, plant growth has had winding properties. What’s more, the ferns in the fossils are “left-handed” and grow in the left-handed direction.

Previously, researchers have found another 16 million-year-old plant fossil in the “Shanwang Plant Group” in Shandong, China, in which the plant is also a “left-handed”. The two are far from each other, helping researchers better understand the growth patterns of ancient plants.

More than 90% of the entangled plants that live on Earth now grow in a right spiral. Although the reason why ancient plant fossil specimens prefer left-handed is unknown, “we must point out”. After consulting a large number of literatures and studying the fossil specimens, Zhou Weiming and Chinese, Czech and American paleontologists published the results in Current Biology.

Plant edition of Pompeii ancient city in China

“Understanding the trees in ancient forests is important all over the world. “C. Kevin Boyce, one of Zhou’s partners, told The Chinese Journal of Science that the roots of plants that fell into the ground, piled up and formed the coal they see today after a series of biochemical and physical reactions.

If we can solve the mystery of ancient plant fossil sacs, it is like witnessing the transformation of the Bohai Mulberry Field. But where was the once Bohai Sea?

In 1999, Zhou Weiming’s mentor, Wang Jun, a researcher at the Nangu Institute of the Chinese Academy of Sciences, saw a fossil specimen of a plant brought back by his mentor, Wu Xiuyuan, from Uda, Inner Mongolia. Knowing that the specimen was extremely complete, Wang Jun was “delighted” and immediately left with his colleagues for Uda. Until 2003, Wang Jun continued to find new specimens of intact plant fossils in Uda, which were different from the previous “lying” form, many of which were in an upright state and very dense, with one every three to five meters.

With more and more fossil specimens found, and the presence of thick volcanic ash in the area, Wang Jun and others thought that these upright plants were likely to be buried instantly by volcanic ash as the ancient city of Pompeii. Wang Jun in an interview with the media recalled that in Uda, he and his colleagues have done more than 1100 square meters of investigation, and finally confirmed that in the northwest corner of Helan Mountain about 20 square kilometers of the area of a plant version of Pompeii ancient city.

The study was officially published in 2012 and published in the Proceedings of the National Academy of Sciences.

“The Uda coalfield represents a swamp forest that was submerged by volcanic ash, and the trees here lived about 300 million years ago, and some of them are unusual, they may be 40 meters high, and they grow in a way and form that is completely different from the trees we see today. Nature preserves everything in a little-known way. Boyce said.

Paint “Dragon” on the left? Winding direction subverts cognition

In the town of Pompeii, the uda plant, researchers found that many of the original plants were different from what people thought. For example, once in the Middle-aged development, now endangered suth iron plants, its reproductive organs are similar to today’s iron trees, but the leaves are not like the leaves of iron trees generally separate;

In Zhou Weiming et al.’s research, two entangled plant fossil specimens also upended the perception that plants with entanglement ability had appeared on Earth as early as 300 million years ago. The fossil’s ferns are about 1 mm in diameter, and there are “hands” on both sides that assist climbing. The researchers also observed that at least five of the real plants in the two fossil specimens were left-handed, and concluded that the entangled plant was fixed to the left-hand side.

Zhou Weiming told The Chinese Science Daily that plant climbing has a variety of strategies, of which winding climbing is one of the common patterns. “Most of the living plants are fixed right-handed, such as the spin flower plant pull edgy flowers. “There are also plants that can be both left and right, “more than how to make a head”, while very few of the present plants grow in a fixed left-handed mode.

In the existing study, there have been no reports of right-handed winding plant fossils, coupled with previous plant fossils found in the “Shanwang Plant Group”, the world’s only two cases of winding plant fossils are all left-handed winding.

However, “Why are the two cases of winding plant fossils in geological history left-handed?” For scientists who study plant “hands”, Zhou said, this is a question that cannot be answered for the time being, “and there may be deeper natural laws waiting to be discovered”.

Another subversive finding is that in the past it was thought that entangled plants lived on tall trees, but in the fossils they unearthed, ferns were entangled in another smaller plant, and the plant was climbing on hedgehogs and suction cups, somewhat similar to the current climbing tigerand and moon season. “This reveals the complexity of early forest ecosystems. Zhou Weiming said.

Coalfield Treasure Hunt

The process of collecting plant fossils is like a treasure hunt: first use excavators and other large machinery to clean up the rock layer above the fossil layer, 66 cm thick volcanic ash rock exposed to the surface, the researchers will give the sample 1 meter by 1 meter square, and then record each sample plant preservation and measure the size.

If it hadn’t been for Zhou Weiming’s “think more”, the specimens seen today may still lie with other fossils.

Back in Nanjing from the Uda coalfield, Zhou Weiming began to consult the literature. He found that previous studies had speculated on the practice of plant winding. Some researchers pointed out directly in the article, before the geological history of the exact entangled plant fossils only one case found in Shandong Zhongxin World “Shanwang plant group.”

Realizing the importance of the problem, Zhou Weiming found one of the two fossil specimens. Macro-photography with a digital camera, followed by a body microscope to observe the fossil’s locality – the details of subtle hooks, scales and burrs on plants – help to more accurately identify species.

In order to distinguish the categories of entangled plants and host plants, Zhou said, they had to cut the fossils into three parts to get the plant’s anatomy. “Based on the anatomical characteristics, we have to understand that the entangled plant is a real fern, and the host plant is a seed fern. “

“It’s hard for plant fossils to preserve the state they live in, it’s harder to preserve three-dimensional structures, and ‘Plant Pompeii’ is a treasure trove of researchers’ fossils, with the world’s only preservation conditions. Zhou Weiming said.

Related papers: https://doi.org/10.1016/j.cub.2019.10.005

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