Gaviiformes

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 (Europe, Asia and debatably Africa), though prehistoric species were more widespread.

==Classification and evolution== There are five living species, and all are placed in the genus Gavia. The loons were formerly often considered to be the most ancient of the northern hemisphere bird families; this idea grew basically out of the perceived similarity of shape and (probably) habits between loons and the entirely unrelated extinct Cretaceous order Hesperornithiformes. In particular Enaliornis, which was apparently an ancestral and plesiomorphic member of that order, was sometimes used to support claims of Albian (Early Cretaceous) Gaviiformes.