Based on the given information, we can deduce that jellyfish were in existence before trilobites and ammonites.
What is a rock layer?
A rock layer can be defined as a horizontal layer of material that typically makes up a rock and whose composition is most likely of the same constituent materials.
In Science, the top layer of a rock layers comprises constituent materials that are younger (newer) while the lowest layer reresent the oldest constituent material.
Read more on rock layers here: https://brainly.com/question/15619429
