Final answer:
The most recent common ancestor of the two closely related fossils that Dr. Bones found in layer C would likely be found in a stratum below layer C, due to the law of superposition which dictates that older layers are deeper in the stratigraphy.
Step-by-step explanation:
The concept described in the student's question concerns stratigraphy and the law of superposition, which are fundamental concepts in geology and paleontology. Dr. Bones, the fictional paleontologist in the scenario, discovered two fossils in a specific layer (layer C) of sedimentary strata. According to the law of superposition, the strata at the bottom are older than those above because newer layers form on top of the older ones. Therefore, if Dr. Bones's hypothesis is correct, and the two fossils are closely related, their most recent common ancestor would most likely be found in a stratum below layer C. This is because the common ancestor would have existed earlier than the two discovered fossils and thus would have been deposited in an older layer of sediment.
Paleontologists often use fossils for geologic dating and correlation. They can establish the relative ages of fossils by examining which layer of sediment they were found in. Occasionally, a mass extinction event can be identified in the fossil record by a sharp decrease in the variety and number of fossils in a particular layer. Biostratigraphic correlation may come into play when correlating different types of sedimentary rocks by identifying common fossil species within those layers.