Cenozoic

The Cenozoic, from 65 mya to the present, is when modern insect faunas became refined. Many Recent insect families appeared in the Cretaceous, and some even appeared in the Jurassic or Triassic, but several diverse lineages of insects radiated in the Cenozoic: the "higher" mantises, termites, and scale insects (Mantoidea, Termitidae, and Neococcoidea, respectively); many ectoparasitic groups (fleas, lice, batflies); the schizophoran flies; bees and ants; and large lineages of phytophagous insects like the ditrysian Lepidoptera and phytophagan beetles. The Cenozoic is also the geological era for which we have the best fossil record for insects and all life; younger fossil deposits have been least destroyed by constant subduction, faulting, erosion, and other earth processes. Dramatic geological processes occurred during the Cenozoic that had great influences on biotic diversity and evolution. Uplift of some of the largest and highest mountain ranges (Himalayas, Alps, and Rockies) occurred during the Cenozoic, which then created deserts and arid grasslands in their rain shadows. Between 60 and 50 mya was one of the warmest periods in earth history, and now tropical groups ranged nearly worldwide. In the Oligocene the continents reached their present positions (Figure 2.62), and this had tremendous impact on global climates and thus distributions of terrestrial organisms. For example, about 30 mya the Drake Passage - the ocean passage between Australia, Antarctica, and South America - opened up, allowing the circulation of ocean currents around Antarctica. This allowed the cooling and glaciation of Antarctica, though it was not until the Pliocene about 5 mya that the southernmost landmass became fully glaciated. Seeing Antarctica today it is difficult to imagine that only 10 mya lush forests harbored a biota there similar to what is found today in New Zealand and Patagonian South America. Land bridges during the Pliocene and Pleistocene connected Europe, eastern Asia, and North America, and the biotas of North America and South America began to mix when the isthmus of Panama connected about 3 mya. All these events, and more, are beautifully documented in the insect fossil record.

For North America, Cenozoic deposits with insects are entirely restricted to areas west of the Appalachian Mountains, most even being within or west of the Rocky Moun

EOCENE (55-50 MYA)

EOCENE (55-50 MYA)

Tropical everwet Tropical summerwet Desert

Warm temperate cool-cold temperate

2.62. Early Cenozoic (Eocene) continental configurations and climates.

tains. The magnificent monograph by Scudder (1890a) on the North American Cenozoic insects is still an important reference. South America is sparse for Cenozoic deposits, probably because little prospecting has been done. Europe and Asia contain several very impressive deposits.

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