Late Cretaceous Edmontonian
Campanian – Masstrictian
Upper Horseshoe Canyon Formation
The fauna transforms in the middle of the formation Edmontosaurus is replaced by Saurlophus and Hypacrosaurus. The centrosaurines disapear as does Edmontonia. Euplocephalus and Albertosaurus remain.
All the known fossils of Albertosaurus sarcophagus are from Horseshoe Canyon. The upper Horseshoe is dominated by hadrosaurines. Hypacrosaurus had a short, high skull and small fat crest, from the rear of which a solid, bony spike jutted down and back. A high ridge on its back may have acted as a radiator, or been used for display. Euplocephalus had no spines on its sides but bands of bony plates across its back and tail with small bony studs between the bands. Plates jutted up over its shoulder and back, and it may have had floating armor in the skin, or a horny sheath. Unlike most ankylosaurs it had a light skull with looped air passages to warm air before it reached the lungs, and bony shutters to protect the eyes.
All the known fossils of Albertosaurus sarcophagus are from Horseshoe Canyon. The upper Horseshoe is dominated by hadrosaurines. Hypacrosaurus had a short, high skull and small fat crest, from the rear of which a solid, bony spike jutted down and back. A high ridge on its back may have acted as a radiator, or been used for display.
Euplocephalus had no spines on its sides but bands of bony plates across its back and tail with small bony studs between the bands. Plates jutted up over its shoulder and back, and it may have had floating armor in the skin, or a horny sheath. Unlike most ankylosaurs it had a light skull with looped air passages to warm air before it reached the lungs, and bony shutters to protect the eyes. Saurolophus was a flat headed duck billed dinosaur that is found in Asia and North America. Atrociraptor is a relatively small dromaeosaurid most closely related to Deinonychus and Bambiraptor, but with a short, deep face and teeth that lean more towards the throat.
Saurolophus had a prong on the back of its head that may have supported inflatable nose pouches so the animal could bellow at rivals. It had a big, flattened tail and long slender limbs. Its feet had 3 hoofed toes, and its hands had 4 webbed fingers with 2 hoofed. Saurolophus had a flat head, a long straight lower jaw, a toothless beak, and batteries of cheek teeth.