Picture a seabird, a bit like a long-winged, short-necked goose. Now picture it with wings five meters across. Now picture it with teeth.
A fossil skull recently found on the the Isle of Sheppey off the English coast tells us that, 50 million years ago, this winged wonder did patrol the coastal seas from above. The bird, placed in the extinct genus Dasornis, had what one paleontologist called, "sharp, tooth-like projections along the cutting edges of the beak." These "pseudo-teeth" are believed to have re-evolved after the birds as a whole lost their teeth through natural selection. This feature may have made it easier for birds like Dasonis emuinus to grip fish they skimmed from the ocean.
COMMENT: Every answer from prehistory raises a new question. If these "teeth" were good for gripping fish, why didn't modern seabirds (those who live on fish, anyway) retain them? If they were not much of an advantage, why did they emerge at all?
"We open doors,,,which lead to more doors." - Agent Scully on the purpose of the X-Files
Scientific reference:Gerald Mayr, “A skull of the giant bony-toothed bird Dasornis (Aves: Pelagornithidae) from the Lower Eocene of the Isle of Sheppey,” Palaeontology, Vol. 51, Part 5, 2008, pp. 1107–1116.