Porpoises

Porpoises () are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulate

Phocoena is a genus of porpoises with four extant species. {| class="wikitable" |- ! Image !! Scientific name !! Common name !! Distribution |- | 120px|| Phocoena dioptrica || Spectacled porpoise ||circumpolar in cool sub-Antarctic and low Antarctic waters |- | 120px|| Phocoena phocoena || Harbour porpoise ||cooler coastal waters of the North Atlantic, North Pacific and the Black Sea |- |120px || Phocoena sinus || Vaquita ||northern area of the Gulf of California, or Sea of Cortez |- | 120px|| Phocoena spinipinnis || Burmeister's porpoise ||coast of South America |- |}

species of mammal

genus of porpoises

Semirostrum ceruttii is an extinct porpoise that lived between 5 and 1.5 million years ago (Ma), during the Pliocene epoch. The species is highly distinctive due to the extremely long symphysis on the lower jaw, reaching lengths of , while that of a modern porpoise is long. The main hypothesis regarding its use is that it probed along the sediment in the murky estuaries and shores of what is now California in search of food, which would easily be scooped up the symphysis and into the jaws. It is the only known species in the genus Semirostrum. The etymology of the name means "half beak",

Archaeophocaena teshioensis is a species of extinct porpoise from the Late Miocene Koetoi Formation of Japan living around 6.4–5.5 million years ago (mya). The holotype specimen comprises a partial skull. The animal, along with Miophocaena and Pterophocaena, seem to represent an intermediary phase between porpoises and dolphins. The genus name derives from Ancient Greek archaeo, "ancient," and Latin phocaena, "porpoise"; the species name honors the Teshio District where the holotype was discovered.