Hesperornis - (pronounced HES-per-OR-nis)

Hesperornis is an extinct genus of flightless aquatic bird that lived during the Coniacian to Maastrichtian sub-epochs of the Late Cretaceous (89-65 million years ago).

Hesperornis were very large birds, reaching up to 2 metres (6.5 feet) in length. They had virtually no wings and hunted in the waters of the North American Inland Sea, swimming with powerful hind legs.

 

Their feet were probably lobed rather than being webbed as in today's grebes.

Like other Mesozoic birds such as Ichthyornis, Hesperornis had teeth in its beak which were used to hold prey (most likely fish), although in the hesperornithiform lineage they were of a different arrangement than in any other known bird with the teeth sitting in a longitudinal groove rather than in individual sockets.

On land, Hesperornis may or may not have been able to walk. Indeed, the leg skeleton of the hesperornithids was so much adapted to diving that their mode of locomotion while ashore, as well as where it laid its eggs and how it cared for its young is a matter of much speculation.

Some have even pointed out that it cannot be completely ruled out that these birds were ovoviviparous instead of incubating their eggs. In any case, young Hesperornis grew fairly quickly and continuously to adulthood, as is the case in modern birds, but not Enantiornithes.

Hesperornis were preyed upon by large marine carnivores. A Tylosaurus specimen found contained the bones of a Hesperornis in its stomach.

Scientific Classification:

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Hesperornithiformes

Family: Hesperornithidae

Genus: Hesperornis