The biotas of the Nearctic and Palearctic realms are fairly similar. North America and Eurasia were frequently connected by land bridges: eastern North America was attached to Western Europe until the breakup of Laurasia 43 million years ago, and northwestern North America had periodic contact with northeastern Asia over the Bering land bridge during much of the past 60 million years. As a result, many plant and animal species on these continents are closely related. The classical example of discontinuous distribution is the arthropod Pesipatus. It is found in both tropical America and tropical Africa. Another example is closely related species of Araucaria that occur in two different areas of the globe which are widely separated by ocean.
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