Hesperornithinae
Hesperornithinae is an extinct subfamily of flightless seabirds belonging to the order Hesperornithiformes. These birds are known from the Late Cretaceous period, primarily in North America. Hesperornithines were well-adapted to a marine environment, possessing adaptations for swimming and diving. Their most striking feature was their complete lack of wings; any ancestral wing structure had been reduced to vestigial knobs. This flightlessness, combined with their pelvic structure, suggests they were incapable of terrestrial locomotion and likely spent their entire lives in the water.
The diet of hesperornithines consisted of fish and other marine life, which they would have caught using