Fossils of mollusks would be found in lower strata than that of arthropods
Explanation:
Fossils are found in different layers of sedimentary rocks. The fossils of organisms that evolved earlier are found in the lower strata while those evolved later are preserved as fossils in the upper strata. If mollusks evolved before arthropods, fossils of arthropods would be present in upper layers while those of mollusks would be found in deeper layers.
Mollusk fossils will be below arthropod fossils because the law of superposition states that sedimentary rock is formed in layers upward, so basically older is lower than newer
