Geology

The Last Habitat

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Science  14 Jun 2002:
Vol. 296, Issue 5575, pp. 1931
DOI: 10.1126/science.296.5575.1931d

Some of the first animals burrowed through marine sediments in search of food and shelter. These animals, though rarely preserved, left telltale tracks and stirred up finely laid sediments; however, colonization of sediments in freshwater rivers and lakes by burrowing animals proceeded much more slowly. Miller et al. surveyed 10,000 terrestrial sediment samples deposited from the Permian to the Jurassic and found scant evidence of burrowing animals. The few inferred to be present appeared to have moved parallel to the surface and thus did not disturb the bottoms of lakes and rivers or enhance the flux of minerals and organic matter between water and sediment. Today, burrowing fresh water animals are abundant; evidently, they arose and multiplied in the late Mesozoic (about 100 million years ago), long after other habitats (fresh water, land, and air) had been exploited. — BH

Geology30, 527 (2002).

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