Historical Geology Understanding Our Planet\'s Past

of the impact deposits. The evidence suggests that meteorite bombardments

might have contributed to many mass extinctions throughout Earth history.

TERRESTRIAL VERTEBRATES

The Devonian floral landscape was dominated by the true ferns, which are the

second most diverse group of living plants. The whisk ferns, which appeared

at the end of the Silurian, became extinct near the end of the Devonian. Some

ancient ferns attained heights of present-day trees (Fig. 100). The earliest

woody tree, the extinct Archaeopteris,dramatically transformed the planet in

Figure 100Ancient ferns
such as Medullosawere
as tall as present-day
trees.

Historical Geology