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

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

Throughout an occasion referred to as the Cambrian Explosion round 550-520 million years in the past, the primary animals to construct arduous and sturdy skeletons abruptly appeared within the fossil file within the blink of a watch in geologic time. Many of those early fossils are easy hole tubes starting from just a few millimeters to many centimeters in size. Nonetheless, it was virtually solely unknown what animals these skeletons had been manufactured from as a result of they lacked the smooth components essential to determine them as belonging to the principle teams of animals nonetheless alive as we speak.

4 copies Gangtoucunia aspera with intact smooth 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 easy, unbranched tentacles about 5 mm (0.2 in) lengthy. It’s doubtless that they had been used to sting and seize prey equivalent to small arthropods. Fossils additionally present this Gangtukuni had a caecum (open at one finish solely) divided into inner cavities that crammed the size of the tube.

These options are discovered as we speak solely in trendy jellyfish, anemones and their shut family members (generally known as cnidarians), organisms whose smooth components are extraordinarily uncommon within the fossil file. The research reveals that these easy animals had been among the many first to construct the arduous skeletons that make up many of the recognized fossils.

Based on researchers, Gangtukuni would have regarded much like trendy scyphozoan jellyfish polyps with a inflexible tubular construction connected to the underlying substrate. The mouth of the tentacle would prolong outdoors the tube, however may very well be retracted into the tube to keep away from predators. Nonetheless, in contrast to the polyps of residing jellyfish, the tube with Gangtukuni was produced from calcium phosphate, the arduous mineral that makes up our personal tooth and bones. The usage of this materials to construct skeletons has develop into more and more uncommon amongst animals.

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.

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