Baleen Baleen Baleen is a filter-feeder system inside the mouths of baleen whales. The baleen system works by a whale opening its mouth underwater and taking in water. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food source for the whale. Baleen is similar to bristles and consists of keratin, the same substance found in human fingernails and hair. Baleen is a skin derivative. Some whales, such as the bowhead whale, have longer baleen than others. Other whales, such as the gray whale, only use one side of their
Aetiocetus other edentulous, or toothless, mysticetes, the pattern of nutrient foramina is most similar to extant balaenopterids (blue whales and other rorquals) and fossil cetotheres. How did "Aetiocetus" feed, and what did it feed on? Its teeth are reminiscent of the bite-and-swallow strategy of archaeocetes and odontocetes, but they also possessed expanded palates. Modern mysticetes grow their baleen from this expanded palate and use the baleen to trap arthropods and fish in their mouths. This is known as bulk-feeding, in that the whale is not selecting individual prey items and does not use echolocation to find prey, as odontocetes do. Fossil