The pessulus is a delicate bar of

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

connecting the dorsal and ventral extremities of the first pair of bronchial cartilages in the

syrinx In classical Greek mythology, Syrinx () was an Arcadian nymph and a follower of Artemis, known for her chastity. Being pursued by Pan, she fled into the river Ladon, and at her own request was metamorphosed into a reed from which Pan then mad ...

of birds. In some birds such as ''

Anas platyrhynchos The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Argen ...

'' the pessulus may be ossified.

References

Bird anatomy {{Vertebrate anatomy-stub