Commonly called as blue whale because body is blue above and yellow below.
Above whale has massive size measuring 35 meters in length and 1.5 lac kg in weight.
Balaenoptera is longest whale and largest mammal flourishing very well.
Body is divisible into small head, large trunk and tail.
Body contains paddle.like forelimbs, dorsal fin and tail flukes.
Whale contains fringed baleen consisting of two rows of transverse plates of keratin for filtering planktones.
Tail flukes are like two forked lobe of tail fin of fish. They provide strong propulsive thrust allowing upward movement of flukes which cause farward movement of whale.
Tail flukes are operated by strong muscles inserted into hind most vertebrae of tail fluke.
Stability and balance is provided by the paddle like forelimbs acting as hydroplanes.
Tail flukes and dorsal fins are neomorphus i.e., they are only folds of skin without any skeletal support but guided by strong muscles.
Paddle-like forelimbs are adapted for swimming.

Special features

Also called sulfur-bottom whale, the most massive animal ever to have lived, a species of baleen whale that weighs approximately 150 tons and may attain a length of more than 30 metres (98 feet). The largest accurately measured blue whale was a 29.5-metre female that weighed 180 metric tons (nearly 200 short [U.S.] tons), but there are reports of 33-metre catches that may have reached 200 metric tons. The heart of one blue whale was recorded at nearly 700 kg (about 1,500 pounds).