Mysticeten

Mysticeti is the infraorder designation for the baleen whales, one of the two principal suborders of the cetaceans, the other being Odontoceti, the toothed whales. Members of Mysticeti are distinguished by having baleen plates instead of teeth, which they use to filter small prey from seawater. They are found in oceans worldwide and include some of the largest animals on Earth.

Feeding and anatomy in mysticetes rely on baleen, keratinous plates that hang from the upper jaw. Their mouths often feature expandable throat pleats that allow the expansion of the mouth when feeding. Most species feed by taking in large gulps of water and prey and then pushing water out through the baleen while the prey is trapped. Diets typically consist of krill, copepods, and small schooling fish; some species also feed on plankton in bloom conditions.

Major groups within Mysticeti include several families such as Balaenidae (right whales), Balaenopteridae (rorquals, including blue, fin, humpback, sei, and minke whales), Eschrichtiidae (gray whale), and Neobalaenidae (pygmy right whale). Taxonomic arrangements have evolved with molecular evidence, and classification can vary as new data refine relationships among lineages.

Evolution and biology: Mysticeti evolved from toothed ancestors during the late Eocene to early Miocene, developing baleen as a filter-feeding adaptation. They generally have symmetrical skulls and rely less on echolocation than odontocetes. Mysticetes are typically large, long-lived mammals with relatively slow reproductive rates, often giving birth to a single calf after long intervals.

Conservation and distribution: Mysticetes occur in nearly all ocean regions, with many species undertaking long migratory journeys. Historical hunting severely reduced several populations, and contemporary threats include entanglement in fishing gear, ship strikes, and climate-driven changes in prey availability. Some species are protected and recovering, while others remain at risk.