What are the hard parts of life forms found in rocks called?

Which of the following structures of a fish is homologous with the lung of a frog?

Embryological support for evolution was proposed by

The occurrence of vestigial organs is not explained by:

Age of fossils in the past was generally determined by the radio-carbon method and other methods involving radioactive elements found in the rocks. More precise methods,which were used recently and led to the revision of the evolutionary periods for different groups of organisms,include:

Homologous organs are