This type of trilobite is an index fossil that lived about 440 million years ago. Fossils of the trilobite and the brittle star were found in the same rock layer. What can you infer about these two organisms?

Question

Group of answer choices

They are likely closely related.

They likely lived in different habitats.

They are likely younger than the rock layer.

They likely lived at the same time.

Answer 1

Based on the information provided, the best inference is:

They likely lived at the same time.

Since both the trilobite (which is an index fossil that existed around 440 million years ago) and the brittle star were found in the same rock layer, it suggests that they inhabited that region during the same geological period. Index fossils are used to date the strata they are found in and indicate that the organisms lived during a specific time frame.