Not much is known about the Tytthostonyx bird. It was a prehistoric seabird that lived approximately 66 million years ago. This bird was found in the Hornerstown Formation of New Jersey, which is on the border of the Cretaceous-Paleocene boundary.
Paleontologists believe that the Tytthostonyx was closely related to the modern-day pelicans, petrels, and albatrosses. Tytthostonyx is the single species in the Tytthostonygidae family. It was a seabird, so it most likely dined in fish and dove for them in the ocean like its descendants the pelican. This bird is considered to be one of the oldest members of the major seabird group.