500-million-year-old fossils resolve age-old thriller of evolution of life on Earth

500-million-year-old fossils resolve age-old thriller of evolution of life on Earth

Artist's reconstruction of Gangtoucunia Aspera

An artist’s reconstruction of Gangtoucunia aspera because it may need appeared in life on the Cambrian seafloor, about 514 million years in the past. The person within the foreground has a part of his skeleton eliminated to disclose a mushy polyp contained in the skeleton. Creator: Reconstruction by Xiaodong Wang

Scientists have lastly solved a centuries-old thriller of the evolution of life on earth, discovering what the primary animals that made skeletons seemed like. This discovery was made potential by an exceptionally well-preserved assortment of fossils found within the japanese province of Yunnan, China. The outcomes of the research have been revealed on November 2 in a scientific journal Proceedings of the Royal Society B.

Throughout an occasion known as the Cambrian Explosion round 550-520 million years in the past, the primary animals to construct laborious and sturdy skeletons instantly appeared within the fossil report within the blink of a watch in geologic time. Many of those early fossils are easy hole tubes starting from a number of millimeters to many centimeters in size. Nevertheless, it was nearly completely unknown what animals these skeletons have been manufactured from as a result of they lacked the mushy components essential to establish them as belonging to the principle teams of animals nonetheless alive at present.

Diagram of Gangtoucunia aspera

Fossil specimen (left) and diagram (proper) of Gangtoucunia aspera with preserved mushy tissues together with intestine and tentacles. Written by Luc Parry and Guangxu Zhang

4 copies Gangtoucunia aspera with intact mushy tissues, together with intestines and mouthparts, are included in a brand new assortment of 514-million-year-old fossils. They present that the species had a mouth rimmed with a hoop of clean, unbranched tentacles about 5 mm (0.2 in) lengthy. It’s possible that they have been used to sting and seize prey akin to small arthropods. Fossils additionally present this Gangtukuni had a caecum (open at one finish solely) divided into inner cavities that stuffed the size of the tube.

These options are discovered at present solely in fashionable jellyfish, anemones and their shut kinfolk (referred to as cnidarians), organisms whose mushy components are extraordinarily uncommon within the fossil report. The research reveals that these easy animals have been among the many first to construct the laborious skeletons that make up many of the identified fossils.

In keeping with researchers, Gangtukuni would have seemed much like fashionable scyphozoan jellyfish polyps with a inflexible tubular construction connected to the underlying substrate. The mouth of the tentacle would lengthen outdoors the tube, however may very well be retracted into the tube to keep away from predators. Nevertheless, not like the polyps of residing jellyfish, the tube with Gangtukuni was constituted of calcium phosphate, the laborious mineral that makes up our personal enamel and bones. Using this materials to construct skeletons has grow to be more and more uncommon amongst animals.

Gangtoucunia aspera Mouth region

An in depth-up picture of the mouth space of ​​Gangtoucunia aspera exhibiting the tentacles used to seize prey. Written by Luc Parry and Guangxu Zhang

Corresponding creator Dr Luke Parry, Division of Earth Sciences,[{” attribute=””>University of Oxford, said: “This really is a one-in-million discovery. These mysterious tubes are often found in groups of hundreds of individuals, but until now they have been regarded as ‘problematic’ fossils, because we had no way of classifying them. Thanks to these extraordinary new specimens, a key piece of the evolutionary puzzle has been put firmly in place.”

The new specimens clearly demonstrate that Gangtoucunia was not related to annelid worms (earthworms, polychaetes and their relatives) as had been previously suggested for similar fossils. It is now clear that Gangtoucunia’s body had a smooth exterior and a gut partitioned longitudinally, whereas annelids have segmented bodies with transverse partitioning of the body.

The fossil was found at a site in the Gaoloufang section in Kunming, eastern Yunnan Province, China. Here, anaerobic (oxygen-poor) conditions limit the presence of bacteria that normally degrade soft tissues in fossils.

Gangtoucunia aspera Fossils

Fossil specimen of Gangtoucunia aspera preserving soft tissues, including the gut and tentacles (left and middle). The drawing at the right illustrates the visible anatomical features in the fossil specimens. Credit: Luke Parry and Guangxu Zhang

PhD student Guangxu Zhang, who collected and discovered the specimens, said: “The first time I discovered the pink soft tissue on top of a Gangtoucunia tube, I was surprised and confused about what they were. In the following month, I found three more specimens with soft tissue preservation, which was very exciting and made me rethink the affinity of Gangtoucunia. The soft tissue of Gangtoucunia, particularly the tentacles, reveals that it is certainly not a priapulid-like worm as previous studies suggested, but more like a coral, and then I realised that it is a cnidarian.”

Although the fossil clearly shows that Gangtoucunia was a primitive jellyfish, this doesn’t rule out the possibility that other early tube-fossil species looked very different. From Cambrian rocks in Yunnan province, the research team has previously found well-preserved tube fossils that could be identified as priapulids (marine worms), lobopodians (worms with paired legs, closely related to arthropods today), and annelids.

Co-corresponding author Xiaoya Ma (Yunnan University and University of Exeter) said: “A tubicolous mode of life seems to have become increasingly common in the Cambrian, which might be an adaptive response to increasing predation pressure in the early Cambrian. This study demonstrates that exceptional soft-tissue preservation is crucial for us to understand these ancient animals.”

Reference: “Exceptional soft tissue preservation reveals a cnidarian affinity for a Cambrian phosphatic tubicolous enigma” by Guangxu Zhang, Luke A. Parry, Jakob Vinther and Xiaoya Ma, 2 November 2022, Proceedings of the Royal Society B Biological Sciences.
DOI: 10.1098/rspb.2022.1623

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