Author: Carolyn Gramling / Source: Science News
Earth’s earliest land-walking vertebrates didn’t paddle about in freshwater lakes or rivers.
Instead, these four-footed creatures, which appeared about 375 million years ago, lived in the brackish waters of an estuary or delta, researchers report online May 30 in Nature.Early tetrapods, such as Ichthyostega and Acanthostega, lived an amphibious existence between land and sea: They had feet, but also gills and tails made for swimming. A new study by paleontologist Jean Goedert of Université Lyon in France and colleagues suggests that the animals also could have tolerated rapid changes in salinity, such as is found in an estuary.
The researchers analyzed sulfur and oxygen isotopes — forms…
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