included the gull-like Ichthyornithes. Flying Cretaceous seabirds do not exceed wingspans of two meters; piscivorous pterosaurs occupied seagoing niches above this size.

While Hesperornis is not thought to have left descendants, the earliest modern seabirds also occurred in the Cretaceous, with a species called Tytthostonyx glauconiticus, which has features suggestive of Procellariiformes