sciencehabit (1205606) writes "A 520-million-year-old shrimp-like creature known as Fuxianhuia protensa has the oldest known cardiovascular system, researchers report. It was both modern and unsophisticated. A simple, tubelike heart was buried in the creature's belly — or thorax — and shot single blood vessels into the 20 or so segments of its primitive body. In contrast, x-ray scans of the specimen revealed profoundly intricate channels in the head and neck. The brain was well supplied with looping blood vessels, which extended branches into the arthropod's alienlike eyestalks and antennae and rivaled the complexity of today's crustaceans. From this Gordian architecture, the researchers can now speculate about the critter's lifestyle. Its brain required abundant oxygen, so it presumably did a fair amount of thinking."