A 380-million-year-old fish heart found embedded in a piece of Australian sediment has scientists’ pulse racing. Not only is this organ in remarkable condition, but it could also provide clues to the evolution of jawed vertebrates, including you and me.
The heart belonged to an extinct class of jawed armored fish called arthrodires that thrived in the Devonian between 419.2 million and 358.9 million years ago – and that’s 250 million years older than the heart of jawed fish which currently holds the “oldest” title. But despite the fish’s archaism, the positioning of its two-chambered S-shaped ticker has led researchers to observe startling anatomical similarities between the ancient swimmer and modern sharks.
“Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a bigger jump between jawless and jawed vertebrates,” said Professor Kate Trinajstic, vertebrate paleontologist at the Australian University of Curtin and co-author of a new study. on the findings. “These fish literally have their hearts in their mouths and under their gills, just like sharks today,” Trinajstic said.
The study was published Wednesday in the journal Science.
Scientists had additional insight into the exact location of the organ as they were able to observe it in relation to the fish’s fossilized stomach, intestine and liver, a rare occurrence.
“I can’t tell you how truly amazed I was to find a beautifully preserved 3D heart and other organs in this ancient fossil,” Trinajstic said.
Paleontologists encountered the fossil during a 2008 expedition to the GoGo Formation in Western Australia, and it adds to a wealth of information gleaned from the site, including the origins of the teeth and information about the transition fin-limb. 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 relics of fabrics as delicate as nerves and embryos with umbilical cords.
“Most instances of soft tissue preservation are found in flattened fossils, where the soft anatomy is little more than a stain on rock,” said study co-author Professor Per Ahlberg from Uppsala University in Sweden. “We are also very fortunate in that modern scanning techniques allow us to study these fragile soft tissues without destroying them. A few decades ago the project would have been impossible.”
These techniques include neutron beams and X-ray microtomography, which create cross-sections of physical objects that can then be used to recreate virtual 3D models.
Recent discoveries of fish fossils have illuminatedand how much the prehistoric lizard fish .
And study co-author Ahlberg has a reminder for those who might not consider these findings important: that life is, at its most fundamental level, an evolving system.
“The fact that we and all other living organisms with whom we share the planet developed from common ancestry through a process of evolution is no accident,” Ahlberg said. “This is the deepest truth of our existence. We are all connected, in the most literal sense.”