Description

Reconstruction of Eusthenopteron based on specimen p-222. 60 cm long. Hyperrealistic finish.

Anatomically, Eusthenopteron shares many unique features with the earliest known tetrapods. For example, it has a similar pattern of bones that sit in the skull to the forms Ichthyostega and Acanthostega.

Eusthenopteron, like other tetrapodomorph fishes, had internal nostrils, a feature found only in terrestrial animals and sarcopterygians. It had labyrinthodont teeth, a common feature of all early tetrapods.

Like other basal sarcopterygians, the skull of Eusthenopteron was bipartite, hinged about halfway along the intracranial joint.

Eusthenopteron’s notoriety comes from the pattern of its fin endoskeleton, which bears a distinct humerus, ulna, and radius (in the front fin) and a distinct femur, tibia, and fibula (in the pelvic fin). This is the characteristic pattern of tetrapods. It is now known to be a general feature of the fins of all fossil sarcopterygians. These strong fins are thought to have helped Eusthenopteron to crawl during dry periods, in search of a new aquatic habitat.

Such movements out of water were also made possible by the possession of lungs as well as gills. Its dimensions were between 30 and 60 centimetres (12 to 24 in). Its tail was distinctive, as its profile was curved and ended in three points, like a trident. The hind fin must have provided the animal with the ability to make rapid thrusts, essential for both hunting and fleeing.

Bibliography: R. Cloutier (1996). “Taxonomic review of Eusthenopteron foordi.”, Devonian Fishes and Plants of Miguasha, Quebec, Canadá, 487–502, Dr. Friedrich Pfeil, München Daeschler, E.B., Subin, N.H., Jenkins, F.A. 2006. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440: 757-763. E. Jarvik (1980). Basic Structure and Evolution of Vertebrates. Academic Pess