Historical Geology Understanding Our Planet\'s Past

THE REPTILIAN ERA

The reptile age, which had its beginning in the Permian and lasted 200 mil-

lion years, witnessed the evolution of some 20 orders of reptilian families.

Amphibians, which were prominent in the Carboniferous, declined consider-

ably in the Permian because of a preference for life in the water. When the

Carboniferous swamps dried out and were largely replaced with deserts, the

amphibians gave way to the reptiles, which were well adapted to drier cli-

mates. In the latter part of the Permian, the reptiles succeeded the amphibians

and became the dominant land-dwelling animals of the Mesozoic era. The

generally warm climate of the Mesozoic was advantageous to the reptiles and

aided them in colonizing the land.

The increase in the number of reptilian fossil footprints in Carbonifer-

ous and Permian sediments shows the rise of the reptiles at the expense of the

Figure 119Fremont
Canyon with the Henry
Mountains in the
background,Wayne and
Garfield Counties, Utah.
(Photo by J. R. Stacy,
courtesy USGS)

Historical Geology