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Fossil holds new insights into how fish evolved onto land by Staff Writers Calgary, Canada (SPX) Jun 26, 2017
"It's like a snake on the outside, but a fish on the inside." The fossil of an early snake-like animal - called Lethiscus stocki - has kept its evolutionary secrets for the last 340-million years. Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones. Their findings have just been published in the prestigious international research journal Nature. "It forces a radical rethink of what evolution was capable of among the first tetrapods," said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM). Before this study, ancient tetrapods--the ancestors of humans and other modern-day vertebrates - were thought to have evolved very slowly from fish to animals with limbs. "We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like," he said. "But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It's like a snake on the outside but a fish on the inside."
Lethicus' secrets revealed with 3D medical imaging "The anatomy didn't fit with our expectations," explains Pardo. "Many body structures didn't make sense in the context of amphibian or reptile anatomy." But the anatomy did make sense when it was compared to early fish. "We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like," explains Pardo, outlining anatomy that's common in fish but unknown in tetrapods except in the very first. The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus' anatomy.
Changing position on the tetrapod 'family tree' The results match better with the sequence of evolution implied by the geologic record. "Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals," says Anderson. "They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses."
Oxford, UK (SPX) Jun 22, 2017 Huge pulses of volcanic activity are likely to have played a key role in triggering the end Triassic mass extinction, which set the scene for the rise and age of the dinosaurs, new Oxford University research has found. The Triassic extinction took place approximately 200 million years ago, and was proceeded by the dinosaur era. One of the largest mass extinctions of animal life on record, the ca ... read more Related Links University of Calgary Explore The Early Earth at TerraDaily.com
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