Digestive system of humpback whales Digestive system of humpback whales The digestive system of humpback whales ("Megaptera novaeangliae") is adapted to digest tiny crustaceans such as krill, plankton, and small fish (including herring and mackerel) which the whale filters from the ocean using its baleen, a sieve-like structure in the upper jaw. Humpback whales belong to the parvorder baleen whales, which are carnivorous, seasonal feeders. The baleen, a sieve-like structure in the upper jaw made of keratin, is used to filter plankton, among other food sources, from the water. Ventral grooves are expandable concave furrows that line a whale's throat and have the peculiarity of
Baleen whale toothed cetaceans (Archaeoceti) remained unknown until the extinct "Janjucetus hunderi" was discovered in the early 1990s in Victoria, Australia. Like a modern baleen whale, "Janjucetus" had baleen in its jaw and had very little biosonar capabilities. However, its jaw also contained teeth, with incisors and canines built for stabbing and molars and premolars built for tearing. These early mysticetes were exceedingly small compared to modern baleen whales, with species like "Mammalodon" measuring no greater than . It is thought that their size increased with their dependence on baleen. However, the discovery of a skull of the toothed "Llanocetus", the second-oldest