The Onychodontiformes are a group of basal sarcopterygians. The group includes two Late Devonian genera: Onychodus and Strunius. Their position in the sarcopterygian evolutionary tree remains unresolved but they are evidently more primitive than the rhipidistians. Onychodus grew up to 2 m long and had large teeth so it was probably a predator while Strunius was only 10 cm long


The actinistians arose in the Middle Devonian and are represented by fossils up to the Late Cretaceous but they were thought to have died out then until the discovery of the modern coelacanth (Latimeria chalumnae). Some early actinistians lived in freshwater but most of them were marine. Osteopleurus from the Lower Jurassic of North America had a short body with large dorsal, anal and paired fins that were all lobed except the anterior dorsal fin. The tail was divided into three parts and the skull was short although the snout was longer than in the Osteolepiformes

The Lower Jurassic Osteopleurus (Permission provided by Mike Benton)

Fossil of Axelrodichthys - an early coelacanth (Permission provided by David Noakes)

Author: Snorri Sigurdsson (Email: ss4460@bristol.ac.uk)
Last updated: 14 November 2004
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