Scaly "strange tree"

Strange fossils

In 1991, an Australian museum received a strange fossil specimen. It came from a quarry, and its surface had diamond-shaped marks similar to reptile scales. Museum staff were puzzled about its origin, but they eventually ruled out the possibility that the diamond-shaped marks were marks of modern excavation tools, and agreed that the specimen was a true biological impression fossil. However, no one could tell exactly which creature left these strange marks. Thus, the specimen became a mysterious fossil in the museum.

In 2010, with the help of paleontologist Gram, the fossil was finally identified. It turned out to be a fossil impression of the outer skin of an ancient plant called Lepidocarpus. Lepidocarpus has a fish-scale-like outer skin, a thick and straight trunk, a trunk diameter of up to 2 meters at the bottom, a plant height of up to 50 meters, and needle-like leaves.

Lepidoptera existed in the Carboniferous period between 359 million and 299 million years ago, which was the heyday of early land plants on Earth. The name of the Carboniferous period comes from the fact that geologists found a large amount of fossil fuels, coal, formed by the accumulation of lepidoptera, ferns and other early plant remains in the ancient strata of this period. Lepidoptera grows very fast, growing to nearly 50 meters in height in just 15 years, and dies collectively shortly after spores are produced. At that time, lepidoptera covered most of the temperate swamps and forests in Asia, Europe and North America.

It's a fern, not a tree.

Based on a large number of fossil samples, scientists not only have a good understanding of the structure of the lepidopsis, but also feel that these ancient plants are different. Like ferns, the lepidopsis reproduces through spores rather than seeds. The lepidopsis will produce sporangia like corn at the end of the branches. The spores in the sacs fall into the water below the lepidopsis, and are then brought to other lands and begin to germinate.

Lepidoptera is a species of lycophyte. They are not trees, but a general term for a variety of tall ferns, a very primitive type of vascular plant. The emergence of blood vessels gives plants two major advantages: first, vascular tissue is like a pipe for plants to absorb water, making it easier for plants to transport water in their bodies; second, with the support of the hard lignin that makes up the vascular tissue, plants can grow very tall and no longer need to grow close to the ground like non-vascular plants such as mosses.

However, the main tissue supporting the lepidopsis is not the vascular tissue (xylem), but the periderm of the lepidopsis. The periderm of the lepidopsis is particularly thick. The periderm thickness of modern trees is usually only a few millimeters, and the vast majority of the cross-section of the lepidopsis is the periderm, with the xylem accounting for only a small part. It can be seen that the lepidopsis relies on its "skin" to stand firm.

Dense diamond-shaped indentations are found all over the trunk and branches of the fossilized lepidolite, and these indentations are arranged in a spiral pattern. The diamond-shaped indentations on the lepidolite bark are not scales, but scars left by leaves. The lepidolite grows like a bottle brush in its seedling stage, and as it continues to grow, the lower needles fall off, leaving behind unique diamond-shaped scars.

To send off oneself

The roots of lepidodendrons were not as deep as those of today's trees, and a violent storm could blow down entire tracts of them. Lepidodendrons grew quickly and had a short lifespan, so they were very effective carbon fixers, converting atmospheric carbon dioxide into large amounts of organic matter such as cellulose, hemicellulose, and lignin. At the height of their prosperity, nearly half of today's biomass in Europe and North America came from lepidodendrons, which provided shelter and food for giant insects and early reptiles in the Carboniferous period.

However, the super carbon fixation ability of the lepidodendron eventually led to their demise. In the Carboniferous period when the lepidodendron lived, microorganisms were unable to decompose lignin, which means that microorganisms could not decompose the remains of dead lepidodendrons, and could not return the carbon dioxide fixed by the lepidodendrons to the atmosphere. At the same time, too little carbon dioxide in the atmosphere triggered an "inverse greenhouse effect", and the average annual surface temperature dropped year by year. In addition, the eruption products produced by volcanic eruptions rose to the stratosphere, blocking the sunlight that should have shone on the ground for a long time. Various factors caused the earth to enter a very cold ice age, and a large number of plants died during this period. This mass extinction event is called the "Carboniferous Rainforest Collapse Event." The giant dragonfly with a wingspan of 70 cm and the arthropod centipede with a body length of 2.4 meters disappeared in this extinction event.

However, the lepidolite left behind a valuable legacy. The remains of lepidolite and other plants continued to accumulate on the surface and were gradually buried by sediments. Over a long period of time, these early plant remains buried underground gradually dehydrated under high temperature and pressure, forming thick peat layers, which then gradually turned into lignite, bituminous coal, and finally anthracite. Some of this anthracite was used as fuel in thermal power plants to generate electricity, lighting up thousands of homes.