Cetacea

The order Cetacea are marine mammals that live in oceans, seas and even a few rivers around the world. Whales, dolphins and porpoises are part of this group. These common names refer to size: whales are the largest, porpoises the smallest. How and what they eat is a better guide to their relationships. The study of cetaceans is called cetology.

Cetacea
Temporal range: Early Eocene – Present
Humpback stellwagen edit.jpg
Humpback whale breaching
Scientific classification
Kingdom:
Phylum:
Class:
Infraclass:
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Cetacea
Suborders

Mysticeti
Odontoceti
Archaeoceti

Some Cetacea: 1- Bowhead whale; 2- Orca; 3- Right whale; 4- Sperm whale; 5- Narwhal; 6- Blue whale; 7- Rorqual; 8- Beluga

Cetaceans are ocean creatures without toes, but are classified in the related order Cetartiodactyla because their ancestors were even toed ungulates.

Taxonomy

Wikibooks Dichotomous Key has more about this subject: