Question

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?
• They likely lived in different habitats.
• They likely lived at the same time.
• They are likely younger than the rock layer.
• They are likely closely related.

Answer 1

Based on the information provided, the inference that can be drawn is:

**They likely lived at the same time.**

Since both the trilobite (an index fossil that lived approximately 440 million years ago) and the brittle star were found in the same rock layer, it suggests that they coexisted during that period. The other options are not supported by the evidence presented.