Rhizodonts (Order Rhizodontida) are an extinct group of sarcopterygian ('lobe-finned') fishes. They are known from many areas of the world from the Upper Devonian through to the Upper Carboniferous - the earliest known species is about 377 million years old ('Ma'), the latest around 310 Ma.

Rhizodonts lived in tropical rivers and freshwater lakes and were the dominant predators of their age. They reached huge sizes - the largest known species, Rhizodus hibberti from Europe and North America, was an estimated 7 metres in length, making it the largest freshwater fish known. The background image and buttons are a reconstruction of the skull of Screbinodus ornatus (2 metres long) from the UK.

I researched the anatomy and phylogeny of the rhizodonts for my Ph.D. at the University of Cambridge Museum of Zoology (1994-1998), supervised by Dr Jenny Clack.