The earliest known mammals appeared in Late Triassic times, about 220 million years ago. Throughout the Jurassic and Cretaceous, mammals remained only minor elements in the world land faunas, which were dominated by reptiles, and in particular by dinosaurs. Mesozoic mammals were all small shrew- or vole-sized creatures. They lived by scavenging small animals such as insect pupae, caterpillars and beetles. Other early mammals, such as multituberculates, probably exploited plant matter, as do the voles today.
With the close of the Mesozoic Era, the world changed. On land, the major development was the disappearance of the dinosaurs. The succeeding Cenozoic Era began 65 million years ago, and the dominant forms of life on land since then have been flowering plants, insects, birds and mammals.
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