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Next, the researchers went back to look at old foram fossils, using their lithium isotopes to look back in time and calculate past ocean acidity.

With luck, in their case, there will be no problem, for the ratio in foram shells reflects that of the oxygen atoms in the water of the ocean at the time those shells were formed.

While Nummulites are sadly now extinct, there are still plenty of massive foram genera left to admire.

That description applies to far more than one foram… The new squatter has a stark difference from Hospitella – its test is agglutinated, or composed of small particles stuck together.

Because different species with different shell shapes evolved at different times, foram fossils have been widely used to date rocks.