The fossil record shows that some animals, such as the horseshoe crab, have existed unchanged for millions of years. other organisms, such as pigs, have undergone a well-documented sequences of changes. which type of organism would be most useful as an index fossil? explain your answer.

Answer;

Pigs would be more useful as an index fossil.

Explanation; An index fossil is an animal or plant that is preserved in rock record of the earth and has a characteristic of a certain period of geologic time or environment. A useful index fossil must be abundant, easily recognizable, and have a geographic distribution.Pigs would be a useful index fossil because the well-documented changes that occurred in the fossil record would help geologists determine the ages of rocks much more than the unchanging horseshoe crabs.