Younger Fossils Are Often Morphologically Different from Older Fossils in a Lineage

Multiple Choice

Younger fossils are often morphologically different from older fossils in a lineage. How do paleontologists think the morphological transition happened?

A) The younger fossils are a species that underwent anagenesis, gradually evolving a new morphology.
B) The younger fossils are a new species that branched off the older one, rapidly evolving a new morphology.
C) The younger fossils are likely a new species from a different lineage that migrated to the area.
D) a and b
E) none of the above