Through the efforts of a Swedish paleontologist over many decades, Eusthenopteron from the Gaspé is now the best known fossil fish anywhere. Its interior skeleton clearly anticipates that of a terrestrial tetrapod, but in scale, fin and tail, it is undeniably a fish 

Le Prince de Miguasha - a 30 cm long specimen of Eusthenopteron from the Upper Devonian cliffs at Miguasha. Miguasha Museum Collections. This specimen is also featured on a Canada Post stamp. (Photo by BDEC (c).)

In 1925 Joseph Landry, a farmer at Miguasha, Gaspé Peninsula, shipped a large crate to the Swedish Museum of Natural History. Packed inside was a superb half-metre long specimen of Eusthenopteron -- virtually complete and preserved in three-dimensions -- a fish that died 380 million years ago, but in appearance not much different from one lying on a fishmonger's slab. Landry, who collected fish fossils for the museum on commission, was paid $50 for this specimen.

At the museum in Stockholm, the paleoichthyologist Erik Jarvik began a detailed analysis of this specimen of Eusthenopteron. First he serial sectioned the head; that is, grinding it down a fraction of a millimetre at a time, and mapping the detailed distribution of bone and matrix. Thus, he was able to determine the conduit of nerves and blood vessels and the position and shape of glands, organs, and the braincase. Later, he prepared through the scales to expose the vertebral column and the bones supporting the fins. This meticulous work, which was accomplished over decades, was justified by the position this lobe-finned fish occupies in the evolution of land-dwelling tetrapods.

The lobe-finned fishes comprise three groups -- lungfishes, coelacanths and rhipidistians. All of these groups began in the Devonian. The lungfishes are represented today by three genera, the coelacanths by a single genus. The rhipidistians, which includes Eusthenopteron, did not survive the Paleozoic, but this group includes the ancestors of all tetrapods.

Jarvik's work on Landry's specimen of Eusthenopteron was communicated in a remarkable series of papers published from the 1940s through to the '90s. He showed that the skull matches closely those of early amphibians and that the teeth are characterized by complex infolding of the dentine called labyrinthodont, also present in primitive tetrapods. His preparation of the paired belly fins showed that the front fin was supported by bones identifiable as a humerus, ulna and radius, and the rear fins by a femur, fibula and tibia. Clearly, the fins of Eusthenopteron contained the bones of the paired limbs of all tetrapods, although bones distal to a wrist or ankle are not present.

More than 2000 specimens of Eusthenopteron have been collected from the Upper Devonian rocks exposed at the Miguasha cliffs. This striking fossil is the pride of Le Musée d'Histoire Naturelle de Miguasha and has been dubbed, le Prince de Miguasha.

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