Sharks are among the most awe-inspiring fishes in the world, and they have an ancient pedigree extending more than 400 million years, but we know surprisingly little about their origins and subsequent evolution. Dr. Maisey studies extremely rare shark fossils, including some of the earliest shark-like fishes, in order to discover answers to these mysteries. An important aspect of his work involves the use of high-resolution CT-scanning of fossils, to reveal the internal structure of the braincase in both extinct and modern sharks. Although sharks are commonly considered "primitive" or "unevolved," their anatomy is really quite specialized. In particular, their brains and sensory organs have many features not found in other vertebrates. He discovered that the ability of sharks and rays to detect low frequency sound appeared comparatively late in their evolution, but was already well developed in sharks by about 150 million years ago. Dr. Maisey has also discovered that the braincases of some 400-million-year old sharks and bony fishes closely resemble each other, strengthening the view that these groups evolved from a common vertebrate ancestor with jaws. He is now collaborating with colleagues in France, Canada and Australia on the earliest shark fossils, from the Devonian of Bolivia, South Africa, Canada and Western Australia.