Both species feed predominantly on molluscs.

The roof of the upper bill is fringed with plate-like structures ("lamellae") in the African openbill, but these are absent in the Asian openbill.

[2][3] The genus Anastomus was erected by the French naturalist Pierre Bonnaterre in 1791.

[4] The type species was subsequently designated as the Asian openbill (Anastomus oscitans).

[5][6] The name Anastomus is from the Ancient Greek αναστομοω anastomoō meaning "to furnish with a mouth" or "with mouth wide-opened".