Edmontosaurus annectens is a
species of flat-headed or
saurolophine hadrosaurid ornithopod dinosaur (a "duck-billed dinosaur") from the very end of the
Cretaceous Period, in what is now
North America. Remains of
E. annectens have been preserved in the
Frenchman,
Hell Creek, and
Lance Formations. All of these formations are dated to the late
Maastrichtian stage of the
Late Cretaceous Period, representing the last three million years before the
extinction of the dinosaurs (between 67 to 66
million years ago).
Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the
U.S. states of
Montana,
South Dakota,
North Dakota and
Wyoming,
Colorado and the
Canadian province of
Saskatchewan. It was a large animal, up to approximately in length, with an extremely long and low
skull.
E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs. It has a long taxonomic history, and specimens have at times been classified in the genera
Diclonius,
Trachodon,
Hadrosaurus,
Claosaurus,
Thespesius,
Anatosaurus, and
Anatotitan, before being grouped together in
Edmontosaurus.