Ceratodus (lungfish) (seh-RAT-o-dus)

Painting of a lungfish. Its head is sticking out of the shallow water.

Click to zoom.

Lungfishes are freshwater fish with lungs that allow them to breathe air. This supplements the oxygen they get from the water, through their gills. Lungfish are part of an ancient fish lineage that is more closely related to humans and other land-living vertebrates than to most other types of fishes. We know they were abundant and widely distributed during the Cretaceous because because their fossils are common and have been found on all continents except Antarctica. Today, only a few species remain in Africa, South America, and northeastern Australia. The Early Cretaceous lungfish fossils from Maryland, along with similar examples from the western United States, represent some of the last lungfish species to have survived in North America. Scientists don't know yet why their range contracted so dramatically.

This fossil shows the distinctive pointed tooth ridge and rough-textured surface typical of a lungfish tooth plate.

Fragment of a lungfish tooth plate. The hard plates allow lungfish to crush hard foods such as snails. The tooth ridge the texture of the crushing surface are distinctive features of lungfish tooth plates. Click to zoom.

Living lungfish in a fish tank. They have long fins on either side, just behind the head.

These living lungfish were given the genus name Neoceratodus because of their similarity to the extinct lungfish, Ceratodus. Click to zoom.
Susan Middleton © California Academy of Sciences