History Of Reptiles

From studies of fossils and comparative anatomy, biologists infer that reptiles arose from amphibians. The oldest known fossils of reptiles were found in deposits from the early Carboniferous period (359 million to 299 million years ago). The earliest reptiles were small, four-legged vertebrates that resembled lizards and had teeth adapted for eating insects. The abundance of insects at the time may have been one reason the early reptiles flourished. By the Permian period (299 million to 251 million years ago) reptiles had become the dominant land vertebrates.

By the end of the Permian nearly all of the continents had joined to form the supercontinent Pangaea (pan-JEE-uh), shown in Figure 41-1. The interior of Pangaea had a dryer climate than the coastal regions. Reptiles were suited to dry climates and were highly successful. The end of the Permian period (and of the Paleozoic era) is marked by a mass extinction during which a large number of species became extinct. The cause of this extinction is still debated. Reptiles that survived diversified to take over the ecological roles of the extinct species. The Mesozoic era (251 million to 66 million years ago) is often called the Age of Reptiles because nearly all of the large vertebrates during that time were reptiles.

objectives

• Summarize the factors that led to the rise of reptiles as the dominant land vertebrates.

• Identify three factors that contributed to the success of dinosaurs.

• Compare two hypotheses to explain the extinction of the dinosaurs.

• Identify examples of the four modern orders of reptiles.

• Describe three characteristics of modern reptiles that make them well adapted to life on land.

vocabulary dinosaur asteroid impact hypothesis amniotic egg amnion yolk sac allantois chorion albumen keratin

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