Stable isotopes suggest earliest tetrapods were euryhaline creatures
A team of researchers from several institutions in France and China has found evidence that some of the earliest creatures to walk on land likely emerged from estuaries or deltas. In their paper published in the journal Nature, the group describes studying certain stable isotopes in fossil specimens to determine the salinity in which they lived.
Back in 1929, a team of researchers discovered the fossilized remains of Ichthyostega, a tetrapod that was believed to be among the first creatures to walk on land. Since that time, similar types of remains have been found in places like Greenland and China. Study has shown the creatures were able to live both on land and in water—they had four legs, tails for swimming and gills. But until now, scientists reported difficulty in figuring out if the water they came from was fresh or salty (suggesting an ocean existence). In this new effort, the researchers tested 51 ancient fossilized tetrapod bones as a new way to find the answer to this question. Read more.