Paleontologists from China, the United States and United Kingdom have discovered a 3-inch-long fossil of a prehistoric shrimp-like animal with the earliest known cardiovascular system.

The fossil belongs to Fuxianhuia protensa, an extinct arthropod that lived in what is today Yunnan province in China during the Cambrian period, about 520 million years ago.

“This is the first preserved vascular system that we know of,” said Prof Nicholas Strausfeld from the University of Arizona, who is the senior author of a paper published in the journal Nature Communications. Earlier, Prof Strausfeld helped identify the oldest known fossilized brain in a different specimen of Fuxianhuia protensa.

In fact, the vascular system of Fuxianhuia protensa is more complex than what is found in many modern crustaceans.

“Fuxianhuia protensa is relatively abundant, but only extremely few specimens provide evidence of even a small part of an organ system, not even to speak of an entire organ system. The animal looks simple, but its internal organization is quite elaborate. For example, the brain received many arteries, a pattern that appears very much like a modern crustacean,” Prof Strausfeld said.

“Different groups of crustaceans have vascular systems that have evolved into a variety of arrangements but they all refer back to what we see in Fuxianhuia protensa.”

Prof Strausfeld added: “over the course of evolution, certain segments of the animals’ body became specialized for certain things, while others became less important and, correspondingly, certain parts of the vascular system became less elaborate.”

In addition to the exquisitely preserved heart and blood vessels, the Fuxianhuia protensa fossil also features the eyes, antennae and external morphology of the animal.

Using an innovative imaging technique, the paleontologists were able to identify the heart, which extended along the main part of the body, and its many lateral arteries corresponding to each segment.

Its arteries were composed of carbon-rich deposits and gave rise to long channels, which presumably took blood to limbs and other organs.

“With that, we can now start speculating about behavior. Because of well-supplied blood vessels to its brain, we can assume this was a very active animal capable of making many different behavioral choices,” Prof Strausfeld concluded.

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Xiaoya Ma et al. An exceptionally preserved arthropod cardiovascular system from the early Cambrian. Nature Communications 5, article number: 3560; doi: 10.1038/ncomms4560