Before the fossil was found, the plant had been "drifting" for a hundred years

Source: Science and Technology Daily

About 300 million years ago, a volcanic eruption occurred in a tropical rainforest area near the equator, and the ash sealed all the plants. Today, the mainland has drifted to Wuhai City, Inner Mongolia.

Recently, an international team led by Wang Jun, a researcher at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, found a large number of well-preserved fossils of ladybugs in the "Plant Pompeii" in Wuda District, Wuhai City, Inner Mongolia, and confirmed that they are members of the sister taxa of seed plants , former gymnosperms. The research results were published in the Proceedings of the National Academy of Sciences on March 9.

The mystery of life has lasted for a hundred years

Ladybirds are a class of plants that lived 350 million to 250 million years ago, including more than 50 species in more than 20 genera, commonly found in coal formations. It is found in China, Europe and North America. It was once thought to be a euthanthenomorph, wedge leaf, presophobes, or a separate taxon.

"Fossil specimens of such archaic plants were first discovered in the Czech Republic in 1822, and the order Ladybird was established in 1931." Wang Jun said.

Finding a corresponding position in the classification system for the various plants that have been discovered and that have existed on the earth is the most basic disciplinary goal of paleobotanists. But the origins of the ladybirds have always been a mystery.

Study collaborator Dr Jason Hilton from the University of Birmingham in the United Kingdom said that when it was first established, the order Ladybird was considered a unique plant population. Scientists play them around the pitch as a "taxonomic soccer ball," but none of them accomplish the goal of "sorting shots."

Previously, the fossil specimens of The order Ladybuds were relatively small and lacked overall anatomy, so they could not be taxonomically classified. At the same time, the morphology of the order Ladybird varies greatly from place to place.

"For a long time, the reason why the order of the ladybirds was unable to 'recognize the ancestors and return to the ancestors' was the lack of overall morphology and internal anatomical information of the plant." Wang Jun said that the breakthrough of these key features depends on the discovery of fossil specimens with well-preserved appearance morphology and internal anatomical structure.

In 2012, Wang Jun's team discovered a well-preserved "Plant Pompeii" in Wuhai, Inner Mongolia, which contained a large number of complete and exquisite specimens, laying the foundation for exploring the kinship of such plants and their important life evolution significance.

Discover new species of the Ladybird family

Wang Jun believes that it is the volcanic eruption mentioned above that has created excellent burial conditions.

Through the photos taken by Wang Jun at the scene, it can be seen that the plants in the general fossils are lying down, but the fossils of Wuda are standing. The spacing of the fossils is very dense, with an upright plant trunk every three or five meters.

In the restoration map, the tallest tree in the forest is more than 30 meters high, and the smallest is less than the ankle of a person. In the first row of the restoration map, you can see the palm-like ladybirds, which are five or six meters high and upright.

Wang Jun's team discovered a new species of the Ladyleaf family from the "Plant Pompeii" of the Wuhai pseudo-toothed leaf.

In the herbarium of the Nanjing Institute of Geology and Paleontology, this 2.5-ton fossil specimen of the order Ladyleafe completely preserves the appearance of the tree before it was buried in volcanic ash.

At the top of the trunk of the Oohai toothed leaf is a cob-like ear of fruit, which appears to be radially symmetrical, with leaves growing above and below the panicle.

Wang Jun believes that the study unveils the "plant Pompeii", which is a huge treasure trove of fossils and contains many secrets of the ancient plant world. At present, the overall reconstruction of the Wuhai quasi-toothed leaf is only one of them, and the overall reconstruction of a number of new plant species will be announced in the future.

The new species belonged to the former gymnosperms

Researchers used the most advanced experimental instruments in China to anatomical observation of the Wuhai toothed leaf and found that it has the spore propagation mode of ferns and the wood structure of seed plants. Based on these characteristics, it can be confirmed that it is a member of the sister taxon of seed plants, the former gymnosperms.

"Dissecting the leaves, we found symmetrical vascular bundles on either side of the leaf axis. What is even more surprising is that its fruit spikes are also symmetrical vascular bundles on both sides. This is direct evidence that the panicle evolved from the leaf. Dissecting the trunk of the tree, we found that it had a secondary xylem, which was the biggest breakthrough that allowed us to determine the taxonomic characteristics of the tree. Wang Jun explained that these characteristics add up to a typical pre-gymnosperm.

"This type of plant was first seen in the Devonian Period, and from this it evolved seed plants." Wang Jun said that the latifolithtopic age is from the Early Carboniferous to the end of the Permian, a discovery that extends the geological time range of presophytes by about 60 million years.

Presomens represent a group of spore plants that transitioned from spore plants to seed plants during the evolutionary process of the plant kingdom. Previously thought, the pre-gymnosperms were 390 million years from the Middle Devonian to the 310 million years of the Late Carboniferous. The study believes that its existence time should be the middle Devonian-Carboniferous-late Permian.

The study shows that for about 110 million years after seed plants differentiated (360 million years of late Devons), presophthalms, represented by the order Bulbophyllaceae, continued to diversify until the end of the Permian. And independently developed a cones-like reproductive organ, and did not become extinct as rapidly as previously thought.

Despite their reproductive prowess, they were also victims of environmental and climate change during the mass extinction at the end of the Permian. This mass extinction destroyed the world's swamp ecosystems, and with the disappearance of the environment on which the order lived, the order also became extinct.

The determination of the taxonomic location of the order Ladybird also represents a major contribution of Chinese scholars to paleontological taxonomy. Prior to this, more than 40 plant groups of orders were established in the Late Paleozoic Era, except for the order Ladybird and the order Lycoptera, which were completed by foreign researchers.

(Source: Science and Technology Daily; reporter Zhang Ye)