An incredible discovery has finally revealed the first animals to grow a skeleton

Before life on Earth exploded in diversity about 540 million years ago, the first skeletons of primitive animals were already beginning to form.

Spongy-looking marine sponges from this time have been found in tubular thimble-like shapes, organized by hard, mineral filaments – specimens believed to be among the oldest groups of skeletal fossils.

However, there are few other early skeletons in the fossil record, many of which have long lost their soft parts. As a result, it is difficult to determine what the first skeletal creatures on Earth later looked like outside of the hollow tubes – and even harder to classify them.

Many chance fossils from China have defied the odds and are now offering archaeologists a real glimpse into early life forms that lived around 514 million years ago.

Fossils have preserved the soft tissues of four worm-like marine creatures belonging to the species Gangtokonya aspera.

At first, scientists believed that this extinct genus was a close relative of living annelids (like earthworms), which were horizontally segmented. However, these new results indicate Gangtokunya It is closely related to polypeptides, such as jellyfish, sea anemones, and corals.

The mouths of these tubular creatures are surrounded by retractable tentacles about 5 millimeters (0.2 in) long, which may have been used to capture prey. Meanwhile, their intestines take up most of the body and are divided into longitudinal cavities.

The actual form of these creatures is formed externally by a hard mineral known as calcium phosphate, which is also found in human bones.

“This is really a one-in-a-million find,” says the paleontologist. “These mysterious tubes are often found in groups of hundreds of individuals, but so far, they’ve been considered ‘problematic’ fossils because we had no way of classifying them,” says the paleontologist, Luke Barry of Oxford University.

“Thanks to these unusual new specimens, an essential piece of the evolutionary puzzle has been put into place.”

Technical reconstruction Rough G With an individual cut in the front to show off the soft interior. (Xiaodong Wang)

The researchers discovered all four fossils in China’s eastern Yunnan province, where a lack of oxygen allowed soft tissues to evade hungry bacteria.

The crown of tentacles seen on top of these primitive polyps is known to occur only between polyps, including jellyfish, before they develop the free-swimming stage.

As small polyps, jellyfish are shaped like vases, with one end attached to a surface and the other end open to the ocean world. The tentacles at the entrance help to snag prey and bring it into the mouth.

In light of these results, the researchers concluded that Rough G It is an ancient seabed tumor either within or near the cnidarian subclade known as medusozoa.

Most animals in this subclass, called true jellyfish (scyphozoans), eventually develop free-swimming abilities, but some, such as a few species of hydrozoa, remain polyps throughout their lives. Colonies of hydrozoa polyps can build skeletons similar to Rough G Fossils too.

The authors note, “It is interesting that we do not restore a close relationship between them Gangtokunya in a clade with other Medusozoans with exoskeletons of calcium phosphate, suggesting that tube-building materials could have had a complex early evolutionary history, possibly due to convergent losses and reductions of calcium phosphate in skeletons as it became less available during the Paleozoic.

In other words, exoskeletons may not have arisen only once, but likely evolved many times in several different lineages.

G. aspera fossil and graph
fossil Rough G and a simultaneous diagram showing the preserved soft tissue. (Luke Barry and Guangzhou Zhang)

The diversity of the animal’s skeleton may have been a big driver behind the Cambrian explosion itself. However, the sudden appearance of structural diversity in the fossil record may also speak to how difficult it is for delicate strands of vital minerals to stand the test of time.

Even from the little evidence scientists have found, it’s clear that the tube-shaped animals were emerging before the explosion of animal diversity that once took our lives by storm. What led to their expansion remains an open question, although predation is one possibility.

says paleontologist and study author Xiaoya Ma from Yunnan University in China and University of Exeter in the UK.

“This study demonstrates that exceptionally soft tissue preservation is critical for us to understand these ancient animals.”

The study was published in Proceedings of the Royal Society B Biological Sciences.

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