New Mexico Museum of Natural History and Science

Today, some lungfish burrow into lake or river bottom mud to wait out dry spells (estivate). Some Triassic lungfish did the same, and casts of their burrows are found as fossils. Notice the slightly helical shape of this fossil burrow and the expanded, bulb-like ending. These are characteristic features of the estivation burrows of living and extinct lungfishes. This creature persisted through Triassic.

See a recreation of a Triassic Lungfish in its burrow here.