The world's oldest heart has been found in a 380-million-year-old fossil.
The world's oldest heart has been found in a fish fossil
Experts from Curtin University in Australia discovered the heart in a "beautifully preserved" fossil of an ancient jawed fish. A separate fossilised stomach, intestine and liver were also identified - with the position of the organs similar to that of a modern shark.
The researchers hope that the discovery will shed further light on the evolution of the human body.
Professor Kate Trinajstic, who led the study, said: "Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a larger gap between jawless and jawed vertebrates.
"These fish literally have their hearts in their mouths and under their gills - just like sharks today."
The fossil was found in the Gogo Formation in Western Australia and the team were stunned to find that the organs were still intact.