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.
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
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.
This large lizard is a relative of todayâ€™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.
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.