Discovered oldest crawls?

The 550-million-year-old find already documents the existence of mobile animals in the Ediacarium

Researchers have discovered a 550-million-year-old prehistoric creature along with its creep - a special find. © Virginia Tech College of Science
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Primeval Traces of Motion: Researchers in China have discovered the 550-million-year-old fossil of a primitive animal - along with its creeping traces. Both the anatomy of the being and the imprints left by it suggest that it was an articulated animal with the ability to move in a straight line. So it could be a very early representative of the so-called Bilateria - that large group of animals, to which man belongs.

In the Ediacarium era 630 to 540 million years ago bizarre creatures romped around our planet. Some of these beings resembled semi-inflated air mattresses, other fractal ferns or elliptical bubbles. For a long time was therefore controversial, whether it was even about animals.

In the meantime, however, it is becoming apparent that the fauna of the Ediacarium was in part surprisingly progressive. Scientists even suspect that the bilateria originated during this phase. Typical of this large group of the animal kingdom is a bilateral symmetry, a clear front and rear end and the ability to move directionally. To her belong all higher animals besides sponges, cnidarians and ctenophores - also the human being.

Fossil body of Yilingia spiciformis (left), its trace (right) and a reconstruction of its appearance (center). © NIGPAS

A primal animal with its traces

Clear fossil evidence that the roots of the "two-sided" date back so far, however, was missing so far. Now, however, a research team led by Zhe Chen of the Chinese Academy of Sciences has found convincing evidence: in the 550-million-year-old sedimentary layers of the so-called Dengying Formation in southern China, they discovered the fossil of a long, narrow creature - along with its fossilized crawl tracks.

The Yilingia spiciformis baptized creature, from which still further representatives in the formation are received, resembles the scientists according to a thousandfiger. It has clearly delineated body segments, is bilaterally symmetrical and has a head and a tail. These traits already suggest that the creature may be an early form of bilateria. display

Indication for mobility

But the most important indication is provided by the traces of his locomotion. Yilingia spiciformis did not move passively during her lifetime. Instead, it must have dragged its body deliberately over the bottom of the ancient sea and have intermittently inserted breaks in between. It left behind several traces that have been preserved to this day. One of them is directly related to the fossil body of the prehistoric so it is clear that Yilingia spiciformis really tested these impressions in the soil.

According to the researchers, the crawl tracks are among the first known traces of movement of an animal on earth. "This discovery shows that articulated and ready-to-move animals developed 550 million years ago, " notes co-author Shuhai Xiao of Virginia Tech in Blacksburg. "It was this form of mobility that enabled animals to leave an impres- sive footprint on the earth - literally as well as metaphorically speaking."

"Highly Significant Fossils"

It remains unclear at which position of the pedigree the cause of the tracks is to be classified exactly. Chen's team, however, suspects a relationship with arthropods or annelids. However, regardless of the relationship question, it is clear: "This is a remarkable find of highly significant fossils, " emphasizes Rachel Wood of the University of Edinburgh, who was not involved in the study.

"We now have proof that articulated animals moved across the seabed before the Cambrian, and we can connect the trail-bearer directly to the tracks themselves. This is unusual and provides new insights into an important step in animal evolution, "concludes the researcher. (Nature, 2019; doi: 10.1038 / s41586-019-1522-7)

Source: Nature Press / Virginia Tech / Chinese Academy of Sciences

- Daniel Albat