T
his chapter examines the evolution of the reptiles during the Permian
period and covers the greatest mass extinction in Earth history. The
Permian, from 280 to 250 million years ago, was named for a well-
exposed sequence of marine rocks and terrestrial redbeds on the western side
of the Ural Mountains in the Russian district of Perm. Rocks of Permian age
are distinct in western North America, particularly Texas, Nevada, and Utah
(Fig. 119). Important reserves of oil and natural gas reside in the Permian
Basin of Texas and Oklahoma. Extensive coal deposits of Permian age exist in
Asia, Africa, Australia, and North America.
During the Permian, all major continents were combined into the
supercontinent Pangaea, where widespread mountain building and exten-
sive volcanism were prevalent. The interior of Pangaea was largely desert,
causing the decline of the amphibians in favor of the reptiles. At the end of
the Permian, perhaps the greatest extinction Earth has ever known elimi-
nated more than 95 percent of all species, paving the way for the ascension
of the dinosaurs.
PERMIAN REPTILES
THE AGE OF DESERT INHABITANTS