Hesperornithes

Hesperornitheans Temporal range: Late Cretaceous, 100–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Restored skeleton of Hesperornis regalis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Clade:	Avialae
Clade:	Ornithurae
Clade:	†Hesperornithes Fürbringer, 1888
Subgroups[4]
†Baptornis †Brodavis[1] †Chupkaornis[2] †Enaliornis †Judinornis †Pasquiaornis †Potamornis †Hesperornithidae[3] †Asiahesperornis †Canadaga †Fumicollis †Hesperornis †Parahesperornis
Synonyms
Hesperornithiformes Sharpe, 1899[3]

Hesperornithes is an extinct and highly specialized group of aquatic avialans closely related to the ancestors of modern birds. They inhabited both marine and freshwater habitats in the Northern Hemisphere, and include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and Potamornis, all strong-swimming, predatory divers. Many of the species most specialized for swimming were completely flightless. The largest known hesperornithean, Canadaga arctica, may have reached a maximum adult length of 2.2 metres (7.2 ft).^[5]

Hesperornitheans were the only Mesozoic avialans to colonize the oceans. They were wiped out in the Cretaceous–Paleogene extinction event, along with enantiornitheans and all other non-avian dinosaurs.