Mountains, which are among the most extensive coal beds in the world. Alliga-
tors and crocodiles lived in the high northern latitudes as far north as Labrador,
whereas today they are confined to warm, tropical areas. The duck-billed
hadrasaurs also lived in the Arctic and Antarctic regions.
The positions of the continents might have contributed to the warming
of the climate during most of the Mesozoic. Continents bunched together
near the equator during the Cretaceous allowed warm ocean currents to carry
heat poleward. High-latitude oceans are less reflective than land. So they
absorbed more heat, further moderating the climate.
THE INLAND SEAS
In the late Cretaceous and early Tertiary, land areas were inundated by the
ocean, which flooded continental margins and formed great inland seas. Some
of these split continents in two. Seas divided North America in the Rocky
Mountain and high plains regions. South America was cut in half in the region
that later became the Amazon basin. Eurasia was split by the joining of the
Tethys Sea and the newly formed Arctic Ocean.
The oceans of the Cretaceous were also interconnected in the equator-
ial regions by the Tethys and Central American Seaways (Fig. 168).They pro-
vided a unique circumglobal oceanic current system that made the climate
equable.Mountains were lower and sea levels higher. The total land surface
declined to perhaps half its present size. The Appalachians, which were an
imposing mountain range at the beginning of the Triassic, were eroded down
to stumps in the Cretaceous. Erosion toppled the once towering mountain
ranges of Eurasia as well.
Great deposits of limestone and chalk were laid down in Europe and
Asia,which is how the Cretaceous received its name. Seas invaded Asia,Africa,
Australia, South America,and the interior of North America. About 80 mil-
lion years ago, the Western Interior Cretaceous Seaway (Fig. 169) was a shal-
low body of water that divided the North American continent into the
western highlands and the eastern uplands.The western highlands comprised
the newly forming Rocky Mountains and isolated volcanoes. The eastern
uplands consisted of the Appalachian Mountains.
Eastward of the rising Rocky Mountains was a broad coastal plain com-
posed of thick layersof sediments eroded from the mountainous regions and
extending to the western shore of the interior seaway. These sediment layers
were later lithified and upraised. Today they are exposed as impressive cliffs in
the westernUnited States (Fig.170).Along the coast and extending some dis-
tance inland were extensive wetlands, where dense vegetation grew in the sub-
tropical climate. Inhabiting these areas were fish, amphibians, aquatic turtles,
CRETACEOUS CORALS