Aequornithes, or core water birds, are defined as "the least inclusive clade containing Gaviidae and Phalacrocoracidae".
Aequornithes
Image: Spot billed pelican takeoff white background
Gaviiformes is an order of aquatic birds containing the loons or divers and their closest extinct relatives. Modern gaviiformes are found in many parts of North America and northern Eurasia, though prehistoric species were more widespread.
Gaviiformes
Red-throated loon (G. stellata), the smallest living Gavia species. Some Miocene members of this genus were smaller still.