Nope, if you want to know how dolphins evolved, I would suggest doing your own homework, but since I need to hold your hand and teach you stuff, well here it goes:
The
order Cetacea /sɨˈteɪʃ(i)ə/ includes the
marine mammals commonly known as
whales,
dolphins, and
porpoises.
Cetus is
Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from
Ancient Greek κῆτος (
kētos), meaning "whale" or "any huge
fish or
sea monster". In
Greek mythology, the monster
Perseus defeated was called
Ceto, which is depicted by the
constellation of
Cetus.
Cetology is the branch of marine science associated with the study of cetaceans.
Fossil evidence suggests that cetaceans share a common ancestor with land-dwelling mammals that began living in marine environments around 50 million years ago. Today, they are the
mammals best
adapted to aquatic life. The body of a cetacean is fusiform (spindle-shaped). The forelimbs are modified into flippers. The tiny hindlimbs are
vestigial; they do not attach to the backbone and are hidden within the body. The tail has horizontal
flukes. Cetaceans are nearly hairless, and are insulated from the cooler water they inhabit by a thick layer of
blubber.
Some species are noted for
their high intelligence. At the 2012 meeting in Vancouver, Canada, the
American Association for the Advancement of Science (the world's largest science conference), support was reiterated for a cetacean bill of rights, listing cetaceans as
non-human persons.
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