[Campbell Biology P.530] According to the text and Figure 22.19, which specific fossil disco... | Practice Question

According to the text and Figure 22.19, which specific fossil discovery provides strong support for the hypothesis that cetaceans whales, dolphins, and porpoises are closely related to even-toed ungulates hippopotamuses, pigs, deer, and cows ?

  • A: The astragalus (ankle bone) of early cetaceans like *Pakicetus*, which had a double hump on both ends, similar to pigs and deer.
  • B: Fossils indicating that early cetaceans lost their hind limbs and developed flippers.
  • C: The discovery of cetacean fossils in North America, Pakistan, and Egypt.
  • D: The finding that the earliest cetaceans were aquatic mammals.

Explanation

Figure 22.19 and its accompanying text specifically highlight that the astragalus of early cetaceans like Pakicetus shares a unique double-humped shape with that of pigs, deer, and other even-toed ungulates. This distinct anatomical similarity is presented as strong fossil evidence for their close evolutionary relationship.