They were crushed. Without warning, 520 million years ago an ancient tsunami or storm trapped 50 shrimplike creatures under layer after layer of fine dirt particles and mud in the seabed that formerly covered much of southwest China. But rather than pulverize them, the powdery silt and Cambrian oceanic chemicals preserved the 6-centimeter-long animals, known as Fuxianhuia protensa, with impeccable statuesque detail (top panel). This underwater Pompeii initially revealed the ancestral brains of arthropods—such as spiders, scorpions, and crustaceans—and today, scientists report in Nature Communications the discovery of the oldest known cardiovascular system (lower panel). 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. The ancient arthropod could likely peer around its murky marine environment, taking cues from a relatively advanced visual and sensory system, the researchers say.