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. For example, although the internal ears of sharks and rays have no ear bones like ours, they are specialized to detect very low frequency sounds, and can be used to home in on prey. Dr. Maisey has been able to investigate this feature's anatomical evolution in a series of fossils. 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. More ancient shark fossils did not possess the specializations required for detecting their prey using sound.

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 recently explored for ancient shark fossils in the Falkland Islands, and also intends to search in South Africa and Bolivia, in the hope of discovering what the earliest ancestral jawed vertebrates were like. Traditional wisdom divides the jawed vertebrates into two groups; the Osteichthyes ("bony fishes") and Chondrichthyes ("cartilaginous fishes"). But sharks and their relatives may actually have evolved from bony fishes, in which case the traditional dichotomy of jawed vertebrates is incorrect. This has important implications for how we view our own evolutionary history, for ultimately we too are descended from bony fishes.