THE CLASSIFICATION OF FOSSIL PLANTS 
ceded the present era, and which was concentrated in 
the northern hemisphere. 
During the later Paleozoic age, not only did land 
floras come into their own, but land animals made their 
first appearance. While we have well-preserved fossils 
of land plants from the lower Devonian, and must assume 
that they existed in considerable numbers during Silurian 
and probably Ordovician times, land animals seem to 
have first appeared in Pennsylvanian times and do not 
get fair sized until the Permian period. The plants had 
to be rather highly developed before land animals could 
exist. 
First the amphibians predominated, and later the rep¬ 
tiles. The reptiles come into their own in the Mesozoic 
era. This great epoch is subdivided into the Triassic, 
the Jurassic, and the Cretaceous periods. It was the day 
of the dinosaurs, gigantic reptiles which populated the 
land, the air, and the waters of the earth. Fishes, too, 
continued to flourish. 
Plant life in Mesozoic times is primarily represented 
by large cycads and other gymnosperms, while the Paleo¬ 
zoic was the era of the giant ferns (pteridophytes) and 
seed ferns (pteridosperms). During the Jurassic period 
the first birds appear. In the middle of the Cretaceous 
period, a sudden change in floras occurs. Flowering 
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