Fossils do not represent the end of life? Uncovering the mystery of the magical "boneless fossils"

In natural science museums, we can see biological fossils from different geological historical periods. Most of these fossils are fossils of biological remains. They are formed by the parts left after the death of animals and plants, usually the harder parts, such as dinosaur bones, trilobite armor, nautilus shells, etc. However, in some cases, the formation of fossils is not always accompanied by the death of organisms.

Trilobite fossils

Nautilus fossil

When organisms are alive, their activities can affect the surrounding environment, even if it is just an accidental behavior. As we are all familiar with the saying "an accidental planting of willows can lead to a forest of willows", if organisms continue to move in a fixed environment for a long time, it will cause greater changes or damage. For example, benthic organisms feed, move, and excrete in a sedimentary environment, which stirs, mixes, and destroys the surrounding sedimentary particles. Over time, these behaviors even form forms or structures that are clearly different from the original sedimentary environment. This is the biological disturbance effect, and those forms or structures may form fossils over a long period of geological history, called trace fossils.

Grinding Stone

Unlike body fossils, trace fossils can be produced by any organism, regardless of whether it has hard parts or not. Moreover, different organisms with similar body shapes and behavior patterns can form the same trace fossils, while organisms of the same species will form different trace fossils due to differences in individual body shapes and behavior patterns. Even the same individual organism can form different trace fossils in different sedimentary environments (such as sands with different degrees of softness).

Two-leaf stone

Therefore, if body fossils preserve the appearance and physiological structure of organisms, then trace fossils preserve the behavior and habits of organisms. According to habits, trace fossils can be classified into traces of living, crawling, resting, foraging, eating, and escape, etc. They are manifested in geological structures as various burrows, boreholes, and biological erosion structures. They are not only evidence of the existence of ancient organisms in certain special sedimentary environments, but more importantly, they can allow us to obtain some information that cannot be seen from body fossils. For example, a footprint fossil can provide us with a lot of information such as what kind of organism the owner of the footprint was, in what direction it moved, whether it walked or ran, whether it went voluntarily or was forced to go, etc. At the same time, it can also provide environmental information about the rock strata where they were found, such as salinity, sedimentation conditions, oxygen content, etc.

Dinosaur footprint fossil

The preservation of trace fossils in rock formations also plays a very important role in revealing the reasons, time, and location of trace fossil formation. Trace fossils preserved on the surface of rock formations are called upper reliefs, those preserved inside are called full reliefs, and those preserved on the bottom are called lower reliefs. Although it is difficult to identify and classify the organisms that produce trace fossils, it can provide important information for research on the sedimentary environment and the interspecific relationships between organisms. The above is the content shared in this issue. See you next time if you are interested.

Some pictures are from the Internet