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Exceptionally well preserved 380,000,000 year old heart and other organs discovered

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  • Exceptionally well preserved 380,000,000 year old heart and other organs discovered

    Researchers have uncovered beautifully preserved fossilized hearts and other internal organs such as the liver, stomach and intestines, of ancient armored fish called arthrodires, an order in the placoderms (likely our earliest jawed ancestors), that inhabited a large, tropical shallow-sea reef during the Devonian period (about 380 mya) at a locale called the Gogo Formation in Western Australia's Kimberley region near the town of Fitzroy Crossing.

    Such soft tissue rarely fossilize like the hard bits (bones, shells, teeth...) and when they do, are almost always squished flat, unlike these new discoveries which are preserved in three dimensions. The fossils are approximately 250 million years older than any previously known fish heart.

    As study co-author, Per Ahlberg of the University of Uppsala's Department of Organismal Biology, Evolutionary Biology Center, and who posted here a couple of times before The CRASH, explains, "while fossils give us a reasonably complete picture of the evolution of the skeleton, the equally important soft organs usually don't fossilize at all, which means that we are left guessing about the details of their evolutionary transformation."

    These arthrodires had a S-shaped heart with two chambers, similar to that found in sharks, which was positioned at the front of the shoulder girdle, close to where the hearts of sharks and bony fish today.

    The fossils come from two previously known species, Compagopiscis croucheri and Incisoscutum ritchiei, with 3-D fossils of the latter having been recovered from the Gogo formation previously. Both fish were roughly 25cm (9.8") in length, with shark-like asymmetrical tail fins, and broad, blunt-nosed heads with jaws both bearing teeth and blade-like cutting edges.

    This discovery is shedding a lot of new light on the evolution of fish, and as the lead author, vertebrate paleontologist Kate Trinajstic, the John Curtin Distinguished Professor from Curtin's School of Molecular and Life Sciences and the Western Australian Museum, notes, into the evolution of our own bodies as well.

    "The site is without a doubt one of the world's most important fossil sites for understanding the early evolution of backboned animals, including the origins of the human body plan," Dr. Trinajstic explained, pointing out that these fossils "offers a unique window into how the head and neck region began to change to accommodate jaws, which was a critical stage in the evolution of our own bodies."

    Trinajstic added that, "Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a larger leap between jawless and jawed vertebrates. These fish literally have their hearts in their mouths and under their gills -- just like sharks today."

    The liver they found was large and allowed the arthrodires to remain buoyant, like what is found in sharks found today, and helps to reveal how placoderms had evolved away from the organ arrangement of jawless fish. For instance, in lampreys, the liver is squashed against the heart and envelops it from behind, while in these arthrodires there is a heart-liver separation like what we see in modern jawed vertebrates.

    Again, according to Trinajstic, "The liver was large and enabled the fish to remain buoyant, just like sharks today. Some of today’s bony fish such as lungfish and bichirs have lungs that evolved from swim bladders but it was significant that we found no evidence of lungs in any of the extinct armored fishes we examined, which suggests that they evolved independently in the bony fishes at a later date."


    Source: Heart of our evolution discovered: 380-million-year-old heart


    Researchers have discovered a 380-million-year-old heart -- the oldest ever found -- alongside a separate fossilised stomach, intestine and liver in an ancient jawed fish, shedding new light on the evolution of our own bodies.

    The new research, published today in Science, found that the position of the organs in the body of arthrodires -- an extinct class of armoured fishes that flourished through the Devonian period from 419.2 million years ago to 358.9 million years ago -- is similar to modern shark anatomy, offering vital new evolutionary clues.

    Lead researcher John Curtin Distinguished Professor Kate Trinajstic, from Curtin's School of Molecular and Life Sciences and the Western Australian Museum, said the discovery was remarkable given that soft tissues of ancient species were rarely preserved and it was even rarer to find 3D preservation.

    "As a palaeontologist who has studied fossils for more than 20 years, I was truly amazed to find a 3D and beautifully preserved heart in a 380-million-year-old ancestor," Professor Trinajstic said.

    "Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a larger leap between jawless and jawed vertebrates. These fish literally have their hearts in their mouths and under their gills -- just like sharks today."

    This research presents -- for the first time -- the 3D model of a complex s-shaped heart in an arthrodire that is made up of two chambers with the smaller chamber sitting on top.

    Professor Trinajstic said these features were advanced in such early vertebrates, offering a unique window into how the head and neck region began to change to accommodate jaws, a critical stage in the evolution of our own bodies.

    "For the first time, we can see all the organs together in a primitive jawed fish, and we were especially surprised to learn that they were not so different from us," Professor Trinajstic said.

    "However, there was one critical difference -- the liver was large and enabled the fish to remain buoyant, just like sharks today. Some of today's bony fish such as lungfish and birchers have lungs that evolved from swim bladders but it was significant that we found no evidence of lungs in any of the extinct armoured fishes we examined, which suggests that they evolved independently in the bony fishes at a later date."

    The Gogo Formation, in the Kimberley region of Western Australia where the fossils were collected, was originally a large reef.

    Enlisting the help of scientists at the Australian Nuclear Science and Technology Organisation in Sydney and the European Synchrotron Radiation Facility in France, researchers used neutron beams and synchrotron x-rays to scan the specimens, still embedded in the limestone concretions, and constructed three-dimensional images of the soft tissues inside them based on the different densities of minerals deposited by the bacteria and the surrounding rock matrix.

    This new discovery of mineralised organs, in addition to previous finds of muscles and embryos, makes the Gogo arthrodires the most fully understood of all jawed stem vertebrates and clarifies an evolutionary transition on the line to living jawed vertebrates, which includes the mammals and humans.

    Co-author Professor John Long, from Flinders University, said: "These new discoveries of soft organs in these ancient fishes are truly the stuff of palaeontologists' dreams, for without doubt these fossils are the best preserved in the world for this age. They show the value of the Gogo fossils for understanding the big steps in our distant evolution. Gogo has given us world firsts, from the origins of sex to the oldest vertebrate heart, and is now one of the most significant fossil sites in the world. It's time the site was seriously considered for world heritage status."

    Co-author Professor Per Ahlberg, from Uppsala University, said: "What's really exceptional about the Gogo fishes is that their soft tissues are preserved in three dimensions. Most cases of soft-tissue preservation are found in flattened fossils, where the soft anatomy is little more than a stain on the rock. We are also very fortunate in that modern scanning techniques allow us to study these fragile soft tissues without destroying them. A couple of decades ago, the project would have been impossible."

    The Curtin-led research was a collaboration with Flinders University, the Western Australian Museum, the European Synchrotron Radiation Facility in France, the Australian Nuclear Science and Technology Organisation's nuclear reactor, Uppsala University, Monash University's Australian Regenerative Medicine Institute and the South Australian Museum.



    Source

    © Copyright Original Source



    The abstract from the paper, Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte, along with a summary regarding the heart, can be read below

    A Devonian heart

    Placoderms were some of the earliest jawed vertebrates, and transformations to their morphology inform our understanding of the world of vertebrates that came after. Trinajstic et al. studied three-dimensionally preserved soft tissue organs from Devonian arthrodire placoderms showing changes in the shapes of the heart, liver, and intestines associated with the evolution of the jaws and neck. Additionally, the fossils show that the lungs are absent, refuting the hypothesis that lungs are ancestral in jawed vertebrates. —SNV

    Abstract

    The origin and early diversification of jawed vertebrates involved major changes to skeletal and soft anatomy. Skeletal transformations can be examined directly by studying fossil stem gnathostomes; however, preservation of soft anatomy is rare. We describe the only known example of a three-dimensionally mineralized heart, thick-walled stomach, and bilobed liver from arthrodire placoderms, stem gnathostomes from the Late Devonian Gogo Formation in Western Australia. The application of synchrotron and neutron microtomography to this material shows evidence of a flat S-shaped heart, which is well separated from the liver and other abdominal organs, and the absence of lungs. Arthrodires thus show the earliest phylogenetic evidence for repositioning of the gnathostome heart associated with the evolution of the complex neck region in jawed vertebrates.


    Finally, a video:



    Heart Position Animation


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    "You're by far the worst poster on TWeb" and "TWeb's biggest liar" --starlight (the guy who says Stalin was a right-winger)
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  • #2
    No good images of the fossils themselves so...

    I'm always still in trouble again

    "You're by far the worst poster on TWeb" and "TWeb's biggest liar" --starlight (the guy who says Stalin was a right-winger)
    "Overall I would rate the withdrawal from Afghanistan as by far the best thing Biden's done" --Starlight
    "Of course, human life begins at fertilization that’s not the argument." --Tassman

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