RANCHOLABREAN STAGE

major division of Pleistocene time and deposits in North America (the Pleistocene epoch began about 1,600,000 years ago and ended about 10,000 years ago). The Rancholabrean stage follows the Irvingtonian and was named for the La Brea Tar Pits, Los Angeles, which are noted for their abundant remains of fossil animals. The Rancholabrean apparently includes the span of time covered by the Illinoian glacial stage, the following Sangamon interglacial stage, and the Wisconsin glacial stage, the last major glacial episode to affect North America. The Rancholabrean fauna includes many modern forms, such as skunks, bats, bison, rodents, beavers (including a giant form), bear, antelope, and deer, as well as extinct animals: mammoths, mastodons and sabre-toothed cats. Farther south, tapirs, sloths, peccaries, and armadillos were found. Rancholabrean faunas are widely represented across the United States; many of the fossils found are in an excellent state of preservation. At the end of Rancholabrean times the mammal fauna of North America underwent a drastic reduction in numbers and diversity. This reduction may have been connected with environmental changes. It has been suggested that the arrival of humans in North America was responsible for the widespread extinction. It seems unlikely, however, that humans were present in sufficient numbers or had the technology to cause the extinction of all the animals in question, but they may have dealt the final blow to forms already greatly reduced and vulnerable to his predation.