City of Mesa, AZ

Dinosaur Mountain - Cretaceous Arizona

Sediments from the late Cretaceous Period have been found in scattered localities across southeastern Arizona, and deposits of similar age occur in Utah, New Mexico, and Sonora, Mexico. These areas yield information about the plants and animals of Arizona at this time.

Albertosaurus

Albertosaurus

Albertosaurus

 

The carnivorous Albertosaurus is one of a number of close relatives of the famous Tyrannosaurus rex. These tyrannosaurs were a bit smaller, and lived a bit earlier, than their famous relative. Albertosaurus, or a close relative, is known to occur in the Cretaceous of Arizona.

 

Nasutoceratops

Nasutoceratops

Nasutoceratops

One of the plant eating Ceratopsians, the frilled, and in advanced forms, horned dinosaurs. Ceratopsians originated in Asia, and immigrated to western North America in the Cretaceous. This recently discovered species of horned dinosaur was somewhat smaller than its contemporaries and has unique "bull like" horns. Its remains have so far been recovered in southern Utah and probably southern Arizona.

 

Paleosaniwa

photo of Paleosaniwa replica

This large lizard is a relative of today’s monitor lizards and Australian goannas. Like the monitors, Paleosaniwa was likely an opportunistic predator who would welcome the chance to raid nests of many creatures in the hope of getting an easy meal.

Alphadon

photo of Alphadon with T. rex

The first mammals in North America are found in the early Jurassic Kayenta Formation of Arizona. By the late Cretaceous, mammals with more modern characteristics appeared, including Alphadon, a common opossum-like marsupial. Alphadon likely had an appearance and habits like the modern opossum. This little Alphadon bides his time in a recess near the great Tyrannosaurus.

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