A 380-million-year-old fish heart fossil found buried in a pile of Australian sediment has created a stir among scientists. Because this organ is exceptionally preserved, it may provide clues about the evolution of jawed vertebrates, including ourselves.
The GoGo Formation, a sedimentary deposit in the Kimberley region of Western Australia, is known for its rich fossil record preserving reef life from the Devonian period of the Paleozoic era, including remnants of tissue as delicate as nerves and embryos with umbilical cords.
The heart belonged to an extinct class of armored, jawed fish called arthrodires that flourished during the Devonian period between 419.2 million and 358.9 million years ago, and is 250 million years older than the now-titled “oldest” jawed fish heart. But despite the fish’s very archaic nature, the location of its two-chambered S-shaped heart prompted the researchers to observe surprising anatomical similarities between ancient swimmers and modern sharks.
Kate Trinajstic, a vertebrate paleontologist at Curtin University in Australia and a co-author of the new study, said: “Evolution is often thought of as a series of small steps, but these ancient fossils show a larger leap between jawless and jawed vertebrates. “These fish have their hearts literally in their mouths and under their gills – just like sharks today.”
The study was published in the journal Science.
The scientists were able to study the exact location of the organ well, as they were able to see it in comparison to the rare fossilized stomach, intestine, and liver of the fish. “I can’t tell you how surprised I am to find a beautifully preserved 3-D heart and other organs in this ancient fossil,” says Trinajstic.
“Most cases of soft tissue preservation are found in flattened fossils, where the soft anatomy is little more than a speck in rock. We’re also very lucky that modern scanning techniques allow us to examine these delicate soft tissues without destroying them,” said co-author Professor Per Ahlberg of Uppsala University, Sweden. ten years ago, the project would have been impossible,” he says.
These techniques included neutron beams and X-ray microtomography, which creates cross-sections of physical objects that can then be used to reconstruct virtual 3D models.
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