Anatomical counts in cetaceans: teeth, baleen, vertebrae

Anatomy in figures

1 tooth for the narwhal (the tusk), 600 baleen plates for the bowhead whale, free cervical vertebrae in the beluga (unique among cetaceans). These precise anatomical figures tell the adaptive evolution of each lineage.

Counting in order to compare: teeth, baleen, vertebrae

The number of teeth varies strikingly between odontocetes: 240 to 260 in the Amazon river dolphin and the spinner dolphin, but a single spiralled tusk in the narwhal (sometimes two), and only two functional teeth protruding from the mandible in Cuvier’s beaked whale. The sperm whale has teeth only in the mandible (~40), curiously useless for predation: it swallows its giant squid by suction.

Mysticetes carry instead up to 800 baleen plates of keratin per jaw, whose length runs from a few centimetres (rorquals) to more than 4 metres in the bowhead whale. Vertebrae, for their part, hover around 50; the cervical ones are generally fused (except in river dolphins and the beluga, hence their unusually flexible neck).

Also worth exploring

Anatomy can also be approached through the clickable interactive anatomy, comparative morphometrics, fossil ancestors and diets (teeth vs baleen).