It was once thought cetaceans had evolved from an extinct group of mammals called the mesonychids.If,in the future,it is determined that some organisms currently classified as cetaceans did actually evolve from mesonychids,whereas other cetaceans evolved from artiodactyl stock,then what will be true of the order Cetacea?
A)It will be paraphyletic.
B)It will be polyphyletic.
C)It will need to be modified if classification is to reflect evolutionary history.
D)It will be paraphyletic,and it will need to be modified if classification is to reflect evolutionary history.
E)It will be polyphyletic,and it will need to be modified if classification is to reflect evolutionary history.

Question

Quizplus · Accepted Answer

If it is determined that cetaceans evolved from both mesonychids and artiodactyls, then the order Cetacea would be paraphyletic because it would not include all of the descendants of a common ancestor. However, the classification could be modified to reflect the actual evolutionary history by splitting the order into two or more separate orders. Therefore, the best choice is D, as it includes both aspects of the likely scenario.

It Was Once Thought Cetaceans Had Evolved from an Extinct