Why is the blue whales scienitific name the balaenoptera musculus?

Balaenids are large whales, with an average adult length of 15 to 17 metres (45-50 feet), and weighing 50-80 tonnes. Their principle distinguishing feature is their narrow, arched, upper jaw, which gives the animals a deeply curved jawline. This shape allows for especially long Baleenplates. which is why.. blue whales are placed in this family