For much of the time dinosaurs were lording over the land, sleek marine reptiles called ichthyosaurs were the masters of the sea. The dolphinlike predators had enormous eyes for hunting and grew as long as 20 meters. But paleontologists have long been baffled by their brain structure, because most fossil specimens have been squished flat by marine sediments. One rare exception—discovered in the 1800s in southern England’s Bristol Channel—is a spectacularly preserved, 180-million-year-old ichthyosaur named Hauffiopteryx. Now, using computerized tomography (CT) scanning, researchers have created a 3D digital reconstruction of Hauffiopteryx’s skull, making a “ghost image” of its brain known as a digital endocast (above). The team, which reported its findings online earlier this month in Palaeontology, found that the brain’s optic lobes were particularly large; so were the cerebellum, which controls motor functions, and the olfactory region, where odors are processed. Taken together, the team concludes these features show ichthyosaurs were highly mobile predators with a keen sense of sight and smell.