The ventricles are adjacent chambers in the lower heart. In this case, the scientists said, they were separated by an iron-rich wall, which they said was another clue appearing to confirm this to be a heart. A single tubular structure resembling an aorta led from the left ventricle, they said. The two upper chambers, the atria, were not distinguishable, the scientists said, though they felt certain of their existence when the animal was alive.