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Lobe-Finned Fishes
Photo: A Lobe-Finned Fish, Eusthenopteron foordi.
A lobe-finned fish, Eusthenopteron foordi
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Where are they found? North America

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Fossils of an extraordinary fish were found in 1879 by geologists and palaeontologists from the Geological Survey of Canada. This very ancient, but highly advanced fish species possessed lungs as well as gills, and was able to use its fins as rudimentary feet.

These exciting fossils were found in the Gaspésie region of Quebec, in 375 million-year-old sedimentary rocks. The species was named Eusthenopteron foordi. The Canadian Museum of Nature has these fossils in its collection.

With their lungs and lobe-shaped fins, Eusthenopteron and its close relatives had evolved many of the biological pre-requisites for moving onto a new environment: land. Fishes like Eusthenopteron (the name means "robust fin" in Greek) are ancestors of amphibians and all other land animals. Although closer relatives have since been found, for many years this remarkable fish was thought to be the closest link to the first animals that routinely ventured onto land.

Eusthenopteron belongs to a group of fish called lobe-finned fishes, or sarcopterygians. They were able to move in very shallow water and perhaps onshore by using their muscular, paired fins as rudimentary feet. In fact, the sturdy, lobe-shaped fins of these fish had already evolved the same set of major arm and leg bones as land animals, which came much later. Not all lobe-finned fishes had lungs, but those that did could breathe air when their limb-like fins pushed their heads above the water. Fossils of Eusthenopteron are so well preserved, and have been so carefully studied, that the anatomy of this species is probably better known that that of any other extinct vertebrate.

Eusthenopteron lived in brackish water in a tropical environment, probably on the margins of an estuary. At the time—the Late Devonian geological period—the Gaspésie was about 10° to 15° south of the equator. The land immediately around the basin or estuary was probably low-lying, and the bottom of the basin muddy and silty most of the year.

However, seasonal rains swept mud and sand down into the estuary from streams, burying and preserving what have become the most diverse and well-preserved fish fossils known for the period. The deposits can be seen at the Musée d'histoire naturelle de Miguasha, Parc de Miguasha, Nouvelle, Quebec. Miguasha has been named a UNESCO World Heritage Site due to the importance of its fossils.


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To cite this page for personal use:
“Lobe-Finned Fishes”. [Online]. Natural History Notebooks. Canadian Museum of Nature.
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A coelacanth (Coelacanthus banffensis).
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