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''Morganucodon'' ("Glamorgan tooth") is an early mammaliaform genus that lived during the late Triassic period. It first appeared about 205 million years ago. Unlike many other early mammals, ''Morganucodon'' is well represented by abundant and well preserved, though in the vast majority of cases disarticulated, material. Most of this comes from Glamorgan in Wales (''Morganucodon watsoni''), but fossils have also been found in the Yunnan Province in China (''Morganucodon oehleri''), in various parts of Europe and North America and some at least closely related animals (''Megazostrodon'') are known from exquisite fossils from South Africa.〔Pages 21-33, 174 in Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, ''Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure'', Columbia University Press, New York, 2004 ISBN 0-231-11918-6〕 The name comes from a Latinization of ''Morganuc'', "South Glamorgan in the Domesday Book", the county where it was discovered by Walter Georg Kühne,〔Walter G. Kühne, "On a Triconodont tooth of a new pattern from a Fissure-filling in South Glamorgan", ''Proceedings of the Zoological Society of London'', volume 119 (1949-1950) pages 345-350〕 so it means "Glamorgan tooth". It has acquired the nickname Morgie in the Smithsonian National Museum of Natural History.〔(National Museum of Natural History: Photographs of the new Kenneth E. Behring Family Hall of Mammals )〕 ==Biology== ''Morganucodon'' was a small, plantigrade animal. The tail was moderately long. According to Kemp (2005) "the skull was 2-3 cm in length and a presacral body length of about 10 cm (inches ). In general appearance it would have looked like a shrew or mouse".〔Kemp T.S. 2005. ''The origin and evolution of mammals'', Oxford University Press, page 143. ISBN 0-19-850760-7.〕 There is evidence that it had specialized glands used for grooming, which may indicate that, like present day mammals, it had fur. Like present day mammals of similar size and presumed habit, ''Morganucodon'' was likely nocturnal and spent the day in a burrow. There are no direct fossil evidence, but several lines of evidence point to a nocturnal bottleneck in the evolution of the mammal class, and almost all modern mammals of similar size to ''Morganucodon'' are still nocturnal. Likewise, burrowing was widespread both in the cynodonts and in primitive mammals. The logics of phylogenetic bracketing would make ''Morgunacodon'' nocturnal and burrowing too. The diet appears to have been insects and other small animals, again much like a modern shrew. Like most modern mammal insectivores, it grew fairly quickly to adult size. Unlike its therapsid ancestors, ''Morganucodon'' likely lived a rather short life, similar to those of most small mammals today. Its eggs were probably small and leathery, a condition still found in monotremes. The teeth grew in mammalian fashion, with deciduous teeth being replaced by permanent teeth that were retained throughout the rest of the animal's life.〔Alexander F. H. van Nievelt and Kathleen K. Smith, "To replace or not to replace: the significance of reduced functional tooth replacement in marsupial and placental mammals", ''Paleobiology'', Volume 31, Issue 2 (June 2005) pages 324–346〕 The combination of rapid growth in juveniles and a toothless stage at infancy strongly suggests ''Morganucodon'' raised its young by lactation, indeed, it may have been among the very first animals to do so. The molars in the adult had a series of raised humps and edges that fit into each other, allowing for efficient chewing. Unlike the situation in most later mammals, however, the upper and lower molars did not occlude properly when they first met; as they wore against each other, however, their shapes were modified by wear to produce a precise fit. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Morganucodon」の詳細全文を読む スポンサード リンク
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