500-million-year-old fossils remedy the age-old puzzle of the evolution of life on Earth

Scientists have lastly solved the age-old puzzle of the evolution of life on Earth by revealing what the primary animals to develop skeletons appeared like. This discovery was made attainable by an exceptionally well-preserved assortment of fossils present in China’s jap Yunnan province. The outcomes of the analysis have been revealed on November 2 in a scientific journal Proceedings of the Royal Society B.

Round 550-520 million years in the past, in an occasion known as the Cambrian Explosion, the primary animals to construct arduous and sturdy skeletons immediately appeared within the fossil file within the blink of a geologic eye. Many of those early fossils are easy hole tubes ranging in size from just a few millimeters to many centimeters. Nevertheless, what sort of animal made up these skeletons was virtually fully unknown as a result of they didn’t protect the mushy elements wanted to determine them as belonging to the primary teams of animals which might be nonetheless alive.

4 samples Gangtoucunia aspera mushy tissues nonetheless intact, together with intestines and mouthparts, are included within the new assortment of 514-million-year-old fossils. These point out that this species had a mouth rimmed with a hoop of clean, unbranched tentacles about 5 mm (0.2 in) lengthy. It’s probably that they have been used to chunk and catch prey, similar to small arthropods. Fossils additionally present this Gangtukuni had a blind-ended intestine (opening at just one finish), divided into inner cavities that stuffed the size of the tube.

These are options discovered in the present day solely in trendy jellyfish, anemones and their shut family (generally known as cnidarians), organisms whose mushy elements are extraordinarily uncommon within the fossil file. The research reveals that these easy animals have been among the many first to develop the arduous skeletons that make up a lot of the identified fossil file.

In accordance with the researchers. Gangtukuni would have resembled the fashionable scyphozoan polyps of the medusa, with a inflexible tubular construction anchored to an underlying matrix. The mouth of the tentacle might lengthen exterior the tube, however might retract contained in the tube to keep away from predators. Not like residing jellyfish polyps, nevertheless, the tube Gangtukuni was manufactured from calcium phosphate, the arduous mineral that makes up our personal enamel and bones. The usage of this materials to construct skeletons has turn out to be much less frequent in animals over time.

Corresponding writer 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.

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