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　　Scientists have discovered the world's earliestknown cardiovascular system - heart and bloodvessels - in the fossil of a shrimp-like creaturefrom more than 500 million years ago. The rarefind sheds new light on the evolutionarytimeline of life on Earth.

　　The Yunnan Province in southwestern China is known for rich fossil deposits, but researchershad not expected a fossil so exquisitely preserved as the specimen of the 520-million-year-oldshrimp-like species.

　　The entire cardiovascular system in the Fuxianhuia protensa fossil. (Credit: Xiaoya Ma)

　　Researcher Peiyun Cong with the Yunnan Laboratory for Paleobiology unearthed the fossil,University of Arizona neuroscientist and team member Nicholas Strausfeld said it gaveresearchers the first detailed image of the creature's circulatory system.

　　“The fossil is a beautiful carbon trace, it is bilaterally symmetrical. It shows the dorsal bloodvessel and the lateral vascular components, the arteries, the lateral arteries and then a very,very, beautiful, system of arteries over where the brain sits in the head.”

　　In earlier research with fossils of the same species, the scientists on this project had identifiedits brain, gut and nervous system.

　　Strausfeld says it is common to see fossils with imprints of teeth, shell and bone, but no softtissues because they decay first when a creature dies. He explains how the internal organsmay have fossilized.

　　“We assume that the specimens became entombed by a very sudden event - a sudden burial,maybe an underwater landslide, maybe something to do with a tsunami, who knows, maybe avery, very heavy dust fall out from a storm," he said. "And, then this chemical preservation ofthe internal tissue as it was squashed flat.”

　　This ancient marine species dates from the Cambrian period, a time in Earth’s history whenmajor animal groups began to appear with a huge variety of shapes and forms. Strausfeld saysthe organ systems detailed in this study are easily recognizable in today's crustaceans.

　　“It suggests that already 520 million years ago, the basic layout, what we call the groundpattern, of say a vascular system, had already evolved," he said. "And the ground patternpersists until this day in modified forms.”

　　If we see this ancient shrimp as modern, then, Strausfeld asks, who was the ancestor thatgave rise to its sophisticated and very elaborate set of organs?

　　“This is not going to be easy [to answer] because we do not really have access to any olderdeposits," Strausfeld said. "So what we hope to find in these Chengjiang deposits in China arefossils of organisms that clearly were already ancient by that time, and that might give us a leadinto how these more elaborate systems, these very recognizable elaborate systems, howthese systems maybe originated.”