The vast majority of marine species live on continental shelves, shallow-
water portions of islands, and subsurface rises generally less than 600 feet deep.
The richest shallow-water faunas live in the tropics, which contain large num-
bers of highly specialized organisms. Species diversity also depends on the
shapes of the continents, the width of shallow continental margins, the extent
of inland seas, and the presence of coastal mountains that supply nutrients to
the ocean, all of which are affected by continental motions.
Extensive mountain building is also associated with the movement of
crustal plates. The upward thrust of continental rocks alters patterns of river
drainage and climate, which in turn affects terrestrial habitats.The raising of land
to higher elevations, where the air is thin and cold, spurs the growth of glacial
ice, especially in the higher latitudes. Furthermore, continents scattered in all parts
of the world interfere with ocean currents, which distribute heat over the globe.
During the Jurassic and continuing into the Cretaceous, an interior sea
flowed into the west-central portions of North America (Fig. 157). Massive
Figure 157The middle
Jurassic inland sea in
North America.213JURASSIC BIRDS0 750 Kms0 750 MilesInland
SeaNORTH
AMERICA