Dìzhìxuéjiā yòng yǒukǒngchóng huàshí lái tuīduàn dìcéng de niándài.
Geologists use foraminifera fossils to date rock layers.
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Named for the tiny holes, 孔, in its shell, through which it reaches out thread-like feet. The shells pile up on the sea floor and over time help build limestone and chalk.
