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The Fossil Record of Order Chiroptera Bats are the second-most species group of mammals. In some tropical areas, there are more species of bats than of all other kinds of mammals combined. Bats, small mammals of the order Chiroptera, are a diverse group of over 1000 species living around the world. The fossil record of bats is poor when compared with that of most other kinds of mammals. This is probably because of their small size, typically low population densities, and habitat selection. Their bones and teeth are tiny and fragile, making them difficult to find and less likely to be preserved as fossils.
The earliest bat fossils come from the Eocene layers. According to evolutionary reasoning, these are roughly 50 million years old. Yet they are 100 % bats (there is no trace of any partway development of the wing, for instance). They show evidence of having had fully functioning echolocation.
The Cenozoic era starts with the emergence of the first mammals. Bats are one of the ancient species in the world. They got through evolution during worlds history and keep most of the features they had millions years ago. The bat fossil record is restricted to the Cenozoic era, with the oldest known bats occurring in early Eocene deposits in North America and Europe.
Morphological studies of bats and their fossils tend to show that the ancestry of bats is shared with early primates. Evolutionary relationships within the Chiroptera also are debated and are the subject of intensive research. The Paleocene epoch (65 - 54 millions years ago) marks the beginning of the Cenozoic era and the Tertiary period. Bats were one of the mammals who began to fill niches left open following the end-Cretaceous extinction.
They migrated around the world. In Paleocene bats remained small-sized and exhibit few characteristics of later forms, like swiftness and specialized teeth. Bats, which are the only mammals capable of sustained flight, first appear in the fossil record 55 million years ago. Because light skeletons and paper-thin wings don't preserve well over time, teeth are all that remain of Paleocene bats. Bats' wing structure differs from both pterosaurs and birds. Elastic, membranous wings stretch between arm, body, and leg.
Also, their fingers open out toward the wingtip, like a fan. Because the hind leg is not free for other uses such as walking, bats adopt some unusual habits, such as hanging upside down to rest. Today, bat species make up one-quarter of all mammalian species. The next stage was Eocene Epoch which lasted between 54 - 33 millions years ago.
Early in the Eocene, the global climate remains warm. Bats moved out of the forests into the open spaces, become noticeably larger. As the temperature cools, some groups go extinct, especially those in higher latitudes. They now occupy land and air. By history's standards, the Oligocene is relatively uneventful.
Following the rapid cooling that ends the Eocene, the climate remains cooler and more seasonal. Bats migrated between the continents. In the Miocene, 24 - 5. 3 million years ago, temperatures begin to rise. Land bridges, which form as the oceans recede and as inland waters dry out, encourage new waves of animal migration between continents. Bats had not been adapted to the more severe climate and coarser vegetation, such as giant camels, teeter on the verge of extinction.
Pliocene Epoch (5. 3 - 1. 8 million years ago) was marked by he cooling and drying trend that began in the Miocene epoch continues in the Pliocene. But they face fierce predators. Many Pliocene bats resemble those alive today, but some are considerably larger. Pleistocene Epoch (1. 8 - 0. 01 millions years ago) was the global ice era. The gradual cooling that began in the Eocene continues through the Pliocene. Bats changed as the surroundings changed.
During these "interglacial" periods, species that sought shelter in the warmer south. So, present day bats look nearly the same as their ancestors. They represents one of the most ancient species survived coming through all the evolution eras. References Hill, John E. , James D. Smith. Bats: A Natural History.
University of Texas Press, Austin, 1984. Savage, R. J. G. and M. R.
Long. Mammal Evolution, an Illustrated Guide. Facts of File Publications. New York, 1986.
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Research essay sample on The Fossil Record Of Order Chiroptera
