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    Fossils Show Giant Predatory Sea Scorpions Were Distance Swimmers

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    Specimens of what appear to be the largest eurypterid species found in Australia could shed light on the sudden extinction of the massive arthropods.Most modern scorpions would fit in the palm of your hand. But in the oceans of the Paleozoic era more than 400 million years ago, animals known popularly as sea scorpions were apex predators that could grow larger than people in size.“They were effectively functioning as sharks,” said Russell Bicknell, a paleobiologist at the American Museum of Natural History.New research by Dr. Bicknell and colleagues, published Saturday in the journal Gondwana Research and relying on Australian fossils, reveals that the biggest sea scorpions were capable of crossing oceans, a finding that is “absolutely pushing the limits of what we know arthropods could do,” he said.What are commonly known as sea scorpions were a diverse group of arthropods called eurypterids. They came in many shapes and sizes but are perhaps best known for their largest representatives, which could grow to more than nine feet long. With huge claws, a beefy exoskeleton and a strong set of legs for swimming, the larger sea scorpions most likely ruled the seas.However fearsome these arthropods must have been to Paleozoic prey, they went extinct without much of a bang. The fossil record of eurypterids peaked in the Silurian period, which started about 444 million years ago, and they then abruptly died out after the early Devonian period ended about 393 million years ago.That sudden turn of fate has left scientists bewildered.“They appear, they start doing really well, they get very big, and then they go extinct,” said James Lamsdell, a paleobiologist at West Virginia University who was not involved in the study. “For a while they were so dominant, and then they just burned out.”We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      A Mammoth DNA Discovery Helps Map an Ancient Genome in 3-D

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      In 2018 an international team of scientists — from labs in Houston, Copenhagen, Barcelona and beyond — got their hands on a remarkable biological specimen: a skin sample from a 52,000-year-old woolly mammoth that had been recovered from the permafrost in Siberia. They probed the sample with an innovative experimental technique that revealed the three-dimensional architecture of the mammoth’s genome. The resulting paper was published on Thursday in the journal Cell.Hendrik Poinar, an evolutionary geneticist at McMaster University in Canada, was “floored” — the technique had successfully captured the original geometry of long stretches of DNA, a feat never before accomplished with an ancient DNA sample. “It’s absolutely beautiful,” said Dr. Poinar, who reviewed the paper for the journal.The typical method for extracting ancient DNA from fossils, Dr. Poinar said, is still “kind of cave man.” It produces short fragments of code composed of a four-letter molecular alphabet: A (adenine), G (guanine), C (cytosine), T (thymine). An organism’s full genome resides in cell nuclei, in long, unfragmented DNA strands called chromosomes. And, vitally, the genome is three-dimensional; as it dynamically folds with fractal complexity, its looping points of contact help dictate gene activity.“To have the actual architectural structure of the genome, which suggests gene expression patterns, that’s a whole other level,” Dr. Poinar said.“It’s a new kind of fossil, a fossil chromosome,” said Erez Lieberman Aiden, a team member who is an applied mathematician, a biophysicist and a geneticist and directs the Center for Genome Architecture at Baylor College of Medicine in Houston. Technically, he noted, it is a non-mineralized fossil, or subfossil, since it has not turned to stone.Erez Lieberman Aiden, director of the Center for Genome Architecture at Baylor College of Medicine in Houston.Brandon Thibodeaux for The New York TimesThe trunk of a 39,000-year-old woolly mammoth nicknamed Yuka that also yielded fossil chromosomes in the study.Love Dalén/Stockholm UniversityWe are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      ‘Dune’-like Sandworm Existed Millions of Years Longer Than Thought

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      Researchers examined fossils of the predatory worm and found a new species that persisted for 25 million years after it was believed to have become extinct.With a head covered in rows of curved spines, ancient Selkirkia worms could easily be confused with the razor-toothed sandworms that inhabit the deserts of Arrakis in “Dune: Part Two.”During the Cambrian Explosion more than 500 million years ago, these weird worms — which lived inside long, cone-shaped tubes — were some of the most common predators on the seafloor.“If you were a small invertebrate coming across them, it would have been your worst nightmare,” said Karma Nanglu, a paleontologist at Harvard. “It’s like being engulfed by a conveyor belt of fangs and teeth.”Thankfully for would-be spice harvesters, these ravenous worms disappeared hundreds of million years ago. But a trove of recently analyzed fossils from Morocco reveals that these formidable predators measuring only an inch or two in length, persisted much longer than previously thought.In a paper published today in the journal Biology Letters, Dr. Nanglu’s team described a new species of Selkirkia worm that lived 25 million years after this group of tube-dwellers was thought to have gone extinct.The newly described tubular worms were discovered when Dr. Nanglu and his colleagues sifted through fossils stored in the collection of Harvard’s Museum of Comparative Zoology. The fossils hail from Morocco’s Fezouata Formation, a deposit dating back to the Early Ordovician period, which began around 488 million years ago and spanned nearly 45 million years. This was a dynamic era when holdovers from the Cambrian rubbed shoulders with evolutionary newcomers like sea scorpions and horseshoe crabs.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More