GEOL 104 Dinosaurs: A Natural History

Fall Semester 2006
Dinosaur History II: Time of the Titans and Flowering of the Age of Dinosaurs

Dinosaur History Table

Late Jurassic: the Golden Age of Dinosaurs. The carnosaur-sauropod-stegosaur fauna found in many parts of the world. Best example is in western North America: the Morrison Formation (the REAL Jurassic Park!).

Other good representative assemblages include Tendaguru Group of Tanzania, eastern Africa; various formations in China, Europe, southern Africa.

Jurassic-Cretaceous transition is not marked so much by extinctions as by origin or diversification of various groups.

The central Atlantic Ocean continues to widen during the Cretaceous, dividing the world up into the northern supercontinent of Laurasia (comprised of North America, Europe, and Asia except for India) and the southern supercontinent of Gondwana (comprised of South America, Africa, Antarctica, India, Madagascar, and Australia). Because of the physical separation, the dinosaur communities of the Cretaceous diverge from each other. Laurasia itself was divided up by shallow seaways.

Because of this, world moves from cosmopolitan (faunas generally the same around the world) to provincial (different faunas in different regions).

Another big change in the early part of the Early Cretaceous: the rise of angiosperms:

During the early Early Cretaceous, in Europe and North America (and to a degree, some most of the rest of the world), the carnosaur-sauropod-stegosaur dinosaur community is replaced by a carnosaur-iguanodontian-ankylosaur community. Sauropods remain present, but iguanodontians become some of the most common herbivores.

Best example of this community is the Wealden Group of Europe (includes two of Owen's original members of Dinosauria: Iguanodon and Hylaeosaurus). North American equivalent is the lower part of the Cedar Mountain Formation of Utah.

This faunal type persists in the late Early Cretaceous of western North America in the Cloverly Formation (made famous by Deinonychus) and in eastern North America in the Arundel Formation of Prince Georges County, Maryland.

In eastern Asia during the Early Cretaceous, community of maniraptorans, ceratopsians (especially Psittacosaurus), and ankylosaurids are present. Best preserved is the Jehol Group of China, a series of lake deposits famous for preserving feathers.

Not too much is known for Gondwana during the early Early Cretaceous: some carnosaurs, ceratosaurs, diplodocoids, and titanosaurs.

In Gondwana (especially Argentina and northern Africa during the late Early Cretaceous and early Late Cretaceous, the spinosaur-carnosaur-titanosaur community. Most famous is the early Late Cretaceous Bahariya Formation from the coastal swamps of Egypt.

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Last modified: 14 July 2006