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What is more impressive than a walrus's tusks?

Walruses are known for their impressive tusks, but they have one anatomical feature that stands out even more.

Males of some species of mammal have a baculum, also known as a penis bone or os penis. And walruses have the largest by far, at around a metre long.

Richard Sabin, Principal Curator of Mammals at the Museum, explains what a baculum is, what it's for and why scientists think humans are one of the only primate species without it.

Find out more about bacula and their possible functions