The large-scale international research points to a variety of species that survived the huge extinction event that occurred about 250 million years ago (long before the age of the dinosaurs) and wiped out over 80% of the animals on Earth
Prof. Omri Bronstein, Tel Aviv University Photo: Tom Schlesinger 
Prof. Omri Bronstein, Tel Aviv University dives in the waters of the Gulf of Eilat. Photo by Tom Schlesinger 
Echinometra sp. 
Diadema_Eilat. Photography: Omri Bronstein 
Diadema savignyi – Zanzibar. Photography: Omri Bronstein 
Asthenosoma marisrubri – Eilat. Photography: Omri Bronstein
In a large-scale international study, with the participation of marine biologist Dr. Omri Bronstein from Tel Aviv University, the researchers applied new approaches to dating the evolutionary development of skin strands - bottom-dwelling marine animals, including sea urchins, starfish, sea cucumbers, and more. The researchers combined phylogenetic analysis of the complete genome of 54 different species - of which 18 genomes have never been mapped, and dating Paleontological using fossils of sea urchins, collected from all over the world. To the surprise of the researchers, the findings revealed that many species appeared on the earth about 300 million years ago, a long time (about 50 million years) before the accepted date in science.
These findings led to the conclusion that more species than estimated survived the huge extinction event that wiped out over 80% of the species on Earth 250 million years ago. The researchers: "Beyond the obvious scientific interest, we believe that an in-depth understanding of the species that survived previous extinction events may help us deal with the current extinction event, which has been going on for decades, and was largely caused by humans."
Dr. Omri Bronstein from the School of Zoology and the Steinhardt Museum of Nature at Tel Aviv University participated in the extensive research. Researchers from a variety of research institutions in the USA, England, Chile and Austria also participated. The article was published in the journal eLife.
Dr. Bronstein: "Our research focuses on a system of marine animals known as skin strands ('Kvech' from the tongue for thorn, since most of them bear spines), which includes, among other things, sea urchins, starfish, sea cucumbers, and more. These are bottom-dwelling marine invertebrates, which are of great importance in the study of evolution: in the evolutionary tree, they are found at the junction where the vertebrates diverge from the invertebrates (including the skin fibers).
The strands of skin are a relic of the time when the vertebrates diverged from the invertebrates
The leather spines are also of great importance in the ecological aspect: they are a major player in the marine environment, at any depth and in any area on the planet, and their disappearance from a certain area entails radical changes. (A familiar example: in the 80s of the last century, the population of sea urchins in the Caribbean Sea collapsed due to a disease. As a result, the algae that served as food for the sea urchins proliferated greatly, and the uncontrolled growth of the algae led to the death of the coral reefs. And here: the population of leatherbacks in the Bay of Eilat decreased significantly In recent decades, when on the other hand certain species of sea urchins from the Red Sea (Eilat) arrived and established In thousands of them to the shores of the Mediterranean Sea - two phenomena that arouse fear of disturbing the ecological balance of our shores."
In addition to Dr. Bronstein's words, leather cords are of great economic importance, and some of them are considered a prestigious delicacy in an international market that generates about a billion dollars a year. These are just some of the reasons for the extensive interest and practice in leather cords throughout history, up to the present day."
The current study is the most comprehensive ever conducted on the evolutionary history of skin strands in general and sea urchins in particular. The researchers combined the genetic findings with fossil-based dating - with the aim of mapping the evolutionary history of the skin strands on the timeline as precisely as possible.
According to the researchers, the findings were very surprising as they indicate significant errors in the accepted dating of the split dates (the points of differentiation of species) in the evolutionary tree. In fact, the study revealed that many evolutionary events in the group's history occurred up to 50 million years earlier than previously thought.
Dr. Bronstein: "Our work shows that modern sea urchins began to differentiate into different species about 300 million years ago, and many of them survived the 'Permian-Triassic' extinction event that took place about 252 million years ago, which is the most extensive known on Earth to date . In this event, which probably occurred as a result of extreme climate changes following volcanic eruptions or a meteor impact, approximately 81% of all marine species and approximately 83% of all species that lived on Earth at that time were wiped out. This means that most of the species we know today arose after that dramatic extinction event. Our findings have great significance for the study of evolution in general, and not only for that of sea urchins. They testify that even when we have an abundance of fossils and extensive research on the group, as in the case of the sea urchins, the estimates can be wrong by tens of millions of years. This is another reminder that there is much more hidden than visible in the fascinating study of evolution."
Dr. Bronstein concludes: "Even these days we are in the midst of a widespread extinction event, only this time human activity is a major factor in it. An in-depth study of past extinction events, the reasons that led to their occurrence and the species that managed to survive them, may help us deal with the current extinction. Our research shows that we probably know less than we thought. In another chapter of the research, we propose a method that may reduce the errors in dating based on a combination of genetic and fossil analyses. For the sake of the future of the earth, and the future of the species living on it, including humans, it is important to continue to investigate in depth the history of the creatures found on it, or in one word - evolution."
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