Balea: Diferenzas entre revisións

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Unha '''balea''' é un diverso grupo distributed and diverse group of fully aquatic [[placental mammal|placental]] [[marine mammal]]s. They are an informal grouping within the infraorder [[Cetacea]], usually excluding [[dolphin]]s and [[porpoise]]s. Whales, dolphins and porpoises belong to the order [[Cetartiodactyla]] with [[even-toed ungulate]]s and their closest living relatives are the [[Hippopotamidae|hippopotamuses]], having diverged about 40 million years ago. The two parvorders of whales, [[baleen whale]]s (Mysticeti) and [[toothed whale]]s (Odontoceti), are thought to have split apart around 34 million years ago. The whales comprise eight [[Neontology|extant]] [[Family (biology)|families]]: [[Balaenopteridae]] (the rorquals), [[Balaenidae]] (right whales), [[Cetotheriidae]] (the pygmy right whale), [[Eschrichtiidae]] (the gray whale), [[Monodontidae]] (belugas and narwhals), [[Physeteridae]] (the sperm whale), [[Kogiidae]] (the dwarf and pygmy sperm whale), and [[Ziphiidae]] (the beaked whales).