Animal with first ever skeleton revealed by 500 million year old fossils

Scientists have been able to solve a long-standing puzzle in the evolution of life on earth by revealing the appearance of the first animals to make skeletons thanks to a surprisingly well-preserved collection of fossils dating back 500 million years that has been found in eastern Yunnan. Province, China.

sudden onset

In a geological flash, between 550 and 520 million years ago, during the Cambrian Explosion, the first animals to develop strong, hard skeletons appear in the fossil record. Many of these ancient fossils are just simple hollow tubes that range in length from several millimeters to a few centimeters.

Due to the lack of preservation of the soft parts necessary to distinguish them as belonging to the main groups of animals still alive today, it was almost impossible to determine what type of organisms made these skeletons.

Gangtoucunia Aspera

There are four specimens of Gangtoucunia aspera in the new 514-million-year-old fossil collection that still have their soft tissues, such as their intestines and mouthparts, intact. These prove that the mouth of this species was lined with a ring of smooth, unbranched tentacles 5 mm long. These were probably used to catch and sting prey, such as small arthropods.

Fossils also demonstrate that Gangtoucunia had a blind-ended intestine partitioned off by an internal cavity that ran the full length of the tube and was only open at one end.

These characteristics are present only in contemporary jellyfish, anemones and their close relatives, which are extremely rare soft-bodied organisms in the fossil record. Research demonstrates that these primitive creatures were among the first to develop the hard skeletons that make up the majority of the fossil record.

According to the researchers, with a strong tubular structure rooted in the underlying substrate, Gangtoucunia would have resembled polyps of modern scyphozoan jellyfish. The tentacle’s mouth would have extended past the tube but could have been retracted inside to escape predators.

The Gangtoucunia tube was made of calcium phosphate, a hard mineral that also makes up human teeth and bones, unlike the living polyps of jellyfish. It became less common for animals to use this material to build skeletons over time.

Key Piece of Problematic Fossils

Dr Luke Parry, the study‘s corresponding author from the University of Oxford’s Department of Earth Sciences, said these mysterious tubes are usually seen in groups of hundreds, but until recently there was no There was no way to classify them, so they were considered “problematic” fossils. These remarkable new specimens have helped firmly anchor a crucial piece of the evolutionary puzzle.

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Not a worm but a cnidarian

According to the University of Oxford, the new specimens unequivocally show that, contrary to what had previously been assumed for related fossils, Gangtoucunia was never related to annelid worms such as earthworms, polychaetes and their relatives. It is now evident that the annelids have segmented bodies with a transverse separation from the body, whereas Gangtoucunia had a smooth exterior and a longitudinally divided intestine.

The fossil was discovered in Kunming, in the eastern province of Yunnan, China, in the district of Gaoloufang. The fossil was discovered at a location in Kunming, located in eastern Yunnan province, China, in the village of Gaoloufang. Anaerobic or oxygen-poor conditions, like those in this area, limit the presence of bacteria that typically break down soft tissue in fossils.

Guangxu Zhang, a doctoral student who discovered and collected the specimens, was surprised and unsure of what they were when he first noticed the pink soft tissue at the top end of a Gangtoucunia tube.

He discovered three more specimens bearing soft tissue preservation the following month, which was extremely exciting and caused him to reconsider the affinities of Gangtoucunia. He realized that Gangtoucunia is a cnidarian when he noticed that its soft tissues, especially the tentacles, clearly show that it is not a priapulid-like worm as earlier studies had suggested. Instead, it looks more like coral.

primitive jellyfish

Although the fossil unequivocally demonstrates that Gangtoucunia was a prehistoric jellyfish, it is still possible that some early species of tubular fossils may have had very different appearances. The research team has previously discovered well-preserved tube fossils in Cambrian rocks in Yunnan province that could be classified as priapulids or marine worms, lobopods, which are paired-legged worms closely related to modern arthropods. , and annelids.

Xiaoya Ma, a co-corresponding author from Yunnan University and the University of Exeter, said the Cambrian appears to have seen an increase in the prevalence of tube-dwelling lifeforms, which may have been an adaptive response. to the increased predation pressure of the Early Cambrian. This study shows that excellent soft tissue preservation is essential for our understanding of these extinct animals, reports Phys Org.

The Proceedings of the Royal Society B published the article earlier this month.

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