Mammals are characterized by the following features:
1. Mammals breathe air with lungs.
2. Mammals maintain a constant high body temperature independent of their surroundings.
3. Mammals have a four-chambered heart.
4. As a rule, mammals bear live young. (Two primative mammals are exceptions to this rule: the duckbilled platypus and the spiny anteater both lay eggs.)
5. Mammals nurse their young with milk.
6. Mammals have hair, at least at some stage in their development.
The scientific order Cetacea includes all whales. This large order is further divided
into three suborders: the toothed whales or Odontoceti (killer whales, dolphins,
porpoises, beluga whales, and sperm whales), the baleen whales or Mysticeti (blue whales,
humpback whales, gray whales and right whales), and the Archaeoceti (which are all now
extinct). The word "cetacean" is derived from the Greek word cetus, which
The term "baleen whale" is another name for the scientific suborder
Mysticeti. The word Mysticeti is derived from the Greek word for moustache, mystax.
It may refer to the hairy appearance of the baleen plates, which baleen whales have
instead of teeth. Baleen whales have two external blowholes and are larger in size than
most toothed whales. Baleen whales are sometimes refered to as the "great
1. Most scientists recognize three families of baleen whales:
a. Family Balaenidae (the right whales). Right whales have no dorsal fin, no throat
grooves, and extremely long baleen plates contained in a hugely arched jaw.
b. Family Balaenopteridae (the rorqual whales). Rorqual (from the Norwegian word for
these whales) whales have long streamlined bodies, many throat grooves, a small dorsal
fin, and shorter baleen plates.
c. Family Eschrichtiidae (the gray whale). This family has one
living member, the gray whale. The gray
whale has a few throat grooves, short baleen plates, and a small dorsal hump followed by a
series of bumps.
2. Some scientists recognize a fourth family, Neobalaenidae, which contains the pygmy
right whale. Unlike other members of the right whale family, the pygmy right whale has a
For a list of genera, species, and subspecies, see the Appendix.
1. Modern forms of both odontocetes and mysticetes appear in the fossil record five to seven million years ago. Scientists believe that early whales arose 55 to 65 million years ago from (now extinct) ancient land mammals that ventured back into the sea. These ancestors of present-day whales had teeth and some adaptations for an aquatic life. The relationship between early whales and modern whales is unclear due to a poor fossil record. Scientists agree that ancestors of baleen whales probably had teeth.
2. Early baleen whales appeared around 30 million years ago.
3. By 25 million years ago, early members of the right whale family appeared. The modern genus Balaena appeared about 5 million years ago.
4. Members of the rorqual family appeared about 15 million years ago, including the modern genus Megaptera. The modern genus Balaenoptera appeared about 5 to 10 million years ago.
5. The modern gray whale family, Eschrichtiidae, appeared two million years ago.
Habitat and Distribution
SeaWorld/Busch Gardens Animal Information Database
www.seaworld.org / www.buschgardens.org
©2002 Busch Entertainment Corporation.
All Rights Reserved.