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Rodentia is an order of mammals (Mammalia). Members of the order Rodentia are called rodents.
Size and range of order In terms of number of species — although not necessarily in terms of number of organisms (population) or biomass — rodents make up the largest order of mammals, with over 40 percent of mammalian species belonging to the order.• Their success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide variety of foods.(Lambert, 2000) There are between 2000 and 3000 species of rodents, which are found in vast numbers on all continents except Antarctica, most islands, and in all habitats except for oceans. They are the only placental order other than bats (Chiroptera) to reach Australia without human introduction. Characteristics
Natural history The fossil record of rodents began after the extinction of the dinosaurs 65 million years ago. By the end of the Eocene epoch, beavers and squirrels appeared in the fossil record. They originated in Laurasia, the joined continents of North America, Europe, and Asia. Some species colonized Africa, giving rise to the earliest hystricognaths. From there they rafted to South America, an isolated continent during the Oligocene and Miocene epochs. By the Miocene, Africa collided with Asia, allowing rodents such as porcupines to spread into Eurasia. During the Pliocene, rodent fossils appeared in Australia. Even though marsupials are the prominent mammals in Australia, rodents make up almost 25% of the mammals on the continent. Meanwhile, the Americas became joined and some rodents expanded into new territory; mice headed south and porcupines headed north. Some Prehistoric Rodents Castoroides, a giant beaver Ceratogaulus, a horned burrowing rodent Flores Giant Rat, a rat that grew to a large size on the island of Flores Giant hutias, a group of rodents once found in the West Indies Ischyromys, a primitive squirrel-like rodent Leithia, a giant dormouse Neochoerus pinckneyi, a giant North American capybara that weighed 50 kg Phoberomys pattersoni, the largest known rodent Telicomys, a giant South American rodent Classification The rodents are part of the clades: Glires (along with lagomorphs), Euarchontoglires (along with lagomorphs, primates, treeshrews, and colugos), and Boreoeutheria (along with most other placental mammals). The order Rodentia may be divided into suborders, infraorders, superfamilies and families. Classification scheme: ORDER RODENTIA (from Latin, rodere, to gnaw) Alternate classifications The above taxonomy uses the shape of the lower jaw (sciurognath or hystricognath) as the primary character. This is the most commonly used approach for dividing the order into suborders. Many older references emphasize the zygomasseteric system (suborders Protrogomorpha, Sciuromorpha, Hystricomorpha, and Myomorpha). Several molecular phylogenetic studies have used gene sequences to determine the relationships among rodents, but these studies are yet to produce a single consistent and well-supported taxonomy. Some clades have been consistently produced such as: The positions of the Castoridae, Geomyoidea, Anomaluridae, and Pedetidae are still being debated. Notes | |||||||||||||||||||||||||||||||||||||
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