Ancient Whale Upper Jaw and Skull (IMAGE)
Caption
This image shows the upper jaw and skull of Maiabalaena nesbittae. Whales were the first mammals to evolve baleen, and no other mammal uses any anatomical structure even remotely similar to it to consume its prey. But frustratingly, baleen, whose chemical composition is more like that of hair or fingernails than bone, does not preserve well. It is rarely found in the fossil record, leaving paleontologists without direct evidence of its past or origins. Instead, scientists have had to rely on inferences from fossils and studies of fetal-whale development in the womb to piece together clues about how baleen evolved. "When we talk about whale evolution, textbooks tend to focus on the early stages, when whales went from land to sea," said Nicholas Pyenson, the National Museum of Natural History's curator of marine mammals. "Maiabalaena shows that the second phase of whale evolution is just as important for evolution over big scales. For the first time, we can now pin down the origin of filter-feeding, which is one of the major innovations in whale history."
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Smithsonian
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