Scallops lived before the dinosaurs.
Step-by-step explanation:
In this image of rock layers and fossil records, we can see fossils of two different organisms, one being a dinosaur (predatory by the looks of it) and the other being of scallops. The scallops are found only in one rock layer, and the same is the case with the dinosaur fossil.
This suggests that both the scallops and the dinosaurs lived only during those periods, not before them and not after them. Since the scallops are found at the bottom rock layer, and the dinosaurs in the rock layer above them, with both rock layers being undisturbed, it means that the scallops lived before the dinosaurs. It also means that the scallops didn't existed alongside the dinosaurs, but instead the dinosaurs occurred when the scallops were already extinct.