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The heart was found together with distinct fossilised stomach, intestine, and liver, providing new insight into the development of our own bodies.

The heart was found together with distinct fossilised stomach, intestine, and liver, providing new insight into the development of our own bodies.

The location of the organs in the bodies of the ancient arthrodires, a class of armoured fish that thrived during the Devonian period between 419.2 and 358.9 million years ago, is comparable to that of present sharks, providing crucial new evolutionary clues.

On this, experts said that the prehistoric fossils indicate there may have been a greater evolutionary jump between jawed and jawless vertebrates than is typically believed to have occurred.

Experts reacted to the discovery by saying that these fish essentially have their hearts in their mouths and under their gills, exactly like sharks do today.

These traits, according to experts, were developed in such primitive vertebrates, providing a rare glimpse into how the head and neck region started to adapt to accommodate jaws, a crucial stage in the evolution of our own bodies.

There was one important distinction, though: the fish had a huge liver that allowed it to stay buoyant, just like modern sharks do.

As per the scientists, some of today's bony fish like lungfish and birchers have lungs that evolved from swim bladders but the absence of lungs in any of the extinct armoured fishes examined, suggested 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, and was originally a large reef.