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SThe specialists discovered the oldest molecular sign of animal life, but it did not come from a pile of prehistoric bones. While the vast majority of ancient animals we know come from fossils left by the Cambrian explosion – the period when animal life quickly became diversified – new research shows that there were animals strange long before that, but they did not leave bones or pieces. As the authors of the new Nature Ecology & Evolution study show, the evidence that they left was chemical.
In the new article, an international team of scientists announced the discovery of a biomarker left by members of the kingdom of Animalia between 660 and 635 million years, making it the oldest evidence ever discovered. The biomarker, detected in ancient rocks and oils from Oman, Siberia and India, is a steroidal compound named 26-méthylstigmastane, which is known today only by a species of modern sponges called demosponges.
"This biomarker of steroids is the first evidence that demosponges, and thus multicellular animals, thrived in ancient seas 635 million years ago," said first author Alex Zumberge, Ph.D. on Monday. Zumberge is a PhD student in Earth Sciences at the University of California at Riverside.
Today it is Demospongia are the most diverse group of sponges on the planet. The 8,000 species of demosponges in the world are brightly colored invertebrates that reproduce both sexually and asexually. Sponges, like all animals, have some type of skeleton that gives shape to their bodies, but the skeleton of a sponge usually does not leave behind an identifiable fossil. That's why, looking for signs of life from an old sponge, Zumberge and his colleagues focused on finding distinct and stable biomarkers instead of fossils.
The former spectacular date of the steroid biomarker is important as it demonstrates that the animals lived at least 100 million years before the Cambrian explosion, which occurred There are 540 million years. For a long time, scientists have widely believed that all organisms that lived before the Cambrian explosion were mere single-celled creatures. It is becoming increasingly clear that there were animals floating in ancient seas before the Cambrian explosion – and that traces of some of the oldest animals may come from chemicals, not bone or preserved flesh. The oldest known animal fossil, a 558-million-year-old ribbed oval, was identified in September by fragments of organic matter left by its body.
These new discoveries strongly suggest that the demosponges floated in the marine environments of the Neoporterozoic and even existed as early as the cryogenic period, which stretched from 720 to 635 million years ago. These demosponges may have had no eyes or thorns, but they were animals that were adaptable enough for their offspring to flourish today.
Abstract: Sterane biomarkers conserved in ancient sedimentary rocks are promising for tracking the diversification and ecological expansion of eukaryotes. The first animal biomarkers proposed from Demosponges (Demospongiae) are recorded in a sequence of about 100 million years of Neoproterozoic-Cambrian marine sedimentary strata of the Huqf supergroup, southern basin of Oman. This steroid C30 biomarker, known informally as 24-isopropylcholestane (24-ipc), has the same carbon skeleton as the sterols present in some modern demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since sterols of the-ipc are found in trace amounts in some pelagophytic algae. Here we report a novel fossil sterane biomarker that co-appears with 24-ipc in a late Late Cambrian and Neoproterozoic sedimentary rocks, which has a rare hydrocarbon skeleton found in the taxa of demosponges. existing. This sterane is informally referred to as 26-methylstigmastane (26-month), reflecting very unusual methylation at the end of the steroid side chain. It is the first animal-specific steran marker detected in geological recordings that can be unequivocally linked to precursor sterols reported only from existing demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were predominant in some Late Neoproterozoic marine environments, at least until the cryogenic period.
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