Tag: Richard Dearden

Richard is a PhD student at Imperial College London, supervised by Martin Brazeau. He is studying the evolutionary assembly of the jawed-vertebrate body plan, specifically using the fossil record to understand the early evolution of chondrichthyans, the cartilaginous fishes. In particular he is working on the acanthodian fishes, an enigmatic group of Palaeozoic fishes with cartilaginous skeletons, shark-like scales and fin spines. This group sits at a crucial position in jawed-vertebrate phylogeny and has great potential for providing information on early jawed vertebrate evolution, a potential belied only by the fact that their anatomy seems uniquely well designed to produce rubbish fossils.

Contact Details:

Richard Dearden, Department of Life Sciences, Imperial College London, Silwood Park, Buckhurst Road, Ascot, SL5 7PY, UK.

Fossil focus: Acanthodians

Fossil Focus
by Richard Dearden*1 Introduction: The acanthodians are a mysterious extinct group of fishes, which lived in the waters of the Palaeozoic era (541 million to 252 million years ago). They are characterized by a superficially shark-like coating of tiny scales, and spines in front of their fins (Fig. 1). The acanthodians’ heyday was during the Devonian period, about 419 million to 359 million years ago, but their fossil record stretches back to the Silurian period (around 440 million years ago). One specialized filter-feeding group, the Acanthodiformes, persisted until the end of the Permian period (about 252 million years ago), disappearing in the end-Permian mass extinction. Acanthodian fossils were first described by the eminent Swiss palaeontologist Louis Agassiz during the nineteenth c