Scientific Classification

Order - Cetacea

Cetacea is a scientific order of large aquatic mammals that have forelimbs modified into flippers, a horizontally flattened tail, one or two nostrils at the top of the head for breathing, and no hind limbs. Cetaceans include all whales, dolphins, and porpoises.

The word "cetacean" is derived from the Greek word for whale, kētos.

Living cetaceans are further divided into two suborders: the Odontoceti (toothed whales) and the Mysticeti (baleen whales).

Suborder - Odontoceti

Odontoceti is a scientific suborder of whales characterized by having teeth and a single blowhole. The word "Odontoceti" comes from the Greek word for tooth, odontos.

Odontoceti are characterized by having teeth.

Family - Delphinidae

Scientists group most dolphins in the scientific family Delphinidae, part of the suborder Odontoceti. Delphinids (at least 36 species of ocean dolphins) include such well known dolphins as bottlenose dolphins and common dolphins, as well as pilot whales and killer whales.

bottlenose dolphin, Tursiops truncatus

short-finned pilot whales, Globicephala macrorhynchus

killer whale, Orcinus orca

Genus - Tursiops

Tursiops, which translates as "dolphin-like," is derived from the Latin word Tursio for "dolphin" and the Greek suffix –ops for "appearance".

Most scientists currently recognize two species of bottlenose dolphin — the common bottlenose dolphin, Tursiops truncatus, and the Indo-Pacific bottlenose dolphin, Tursiops aduncus.

Fossil Record

Scientists believe that early whales arose 50 million years ago from (now extinct) primitive mammals that ventured back into the sea. Two small rod-shaped pelvic bones, buried deep in the body muscle of toothed whales, may be remnants of the hind limbs of these primitive mammals.

Modern forms of both odontocetes and mysticetes appear in the fossil record five to seven million years ago.

The genus Tursiops first appears in the fossil record about five million years ago.

Biochemical and genetic studies suggest that even-toed ungulates, especially hippopotamuses (Family Hippopotamidae), are cetaceans' closest living terrestrial relatives.

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