Toothed whale Toothed whale The toothed whales (systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of toothed whales (also called odontocetes) are described. They are one of two living groups of cetaceans, the other being the baleen whales (Mysticeti), which have baleen instead of teeth. The two groups are thought to have diverged around 34 million years ago (mya). Toothed whales range in size from the and vaquita to the and sperm whale. Several species of odontocetes exhibit sexual dimorphism, in that
Channel types Channel types A wide variety of river and stream channel types exist in limnology, the study of inland waters. All these can be divided into two groups by using the water-flow gradient as either "low gradient channels" for streams or rivers with less than two percent (2%) flow gradient, or "high gradient channels" for those with greater than a 2% gradient. Low gradient channels of rivers and streams can be divided into braided rivers, wandering rivers, single thread sinuous rivers (meandering), and anastomosing rivers. The channel type developed depends on stream gradient, riparian vegetation and sediment supply. Braided rivers tend