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.

[12] Their diet consists of small crustaceans, primarily copepods, although some species also eat a significant amount of krill.

[13] Similarities in terms of physical appearances of jawlines and usages between balaenidae and flamingo have been pointed as a result of possible convergent evolution.

They have exceptionally large heads in comparison with their bodies, reaching 40% of the total length in the case of the bowhead whale.

[17][18] After death, the large blubber deposits caused right whales to float to the surface, which facilitated an easier oil harvest.