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''Nanotyrannus'' ("dwarf tyrant") is a potentially dubious genus of tyrannosaurid dinosaur. It is known only from two specimens (possibly three), which may in fact be juvenile specimens of the contemporary ''Tyrannosaurus rex''. ==History== ''Nanotyrannus'' is based on CMNH 7541, a skull collected in 1942 by David Hosbrook Dunkle and described by Charles W. Gilmore in 1946, who classified it as a new species in the tyrannosaur genus ''Gorgosaurus'' as ''G. lancensis''. In 1988, the specimen was re-described by Robert T. Bakker, Phil Currie, and Michael Williams, then the curator of paleontology at the Cleveland Museum of Natural History, where the original specimen was housed and is currently on display. Their initial research indicated that the skull bones were fused, and that it therefore represented an adult specimen. In light of this, Bakker and colleagues assigned the skull to a new genus, named ''Nanotyrannus'' for its apparently small adult size. The specimen is estimated to have been around long when it died. However, a detailed analysis of the specimen by Thomas Carr in 1999 showed that the specimen was in fact a juvenile, leading Carr and many other paleontologists to consider it a juvenile specimen of ''Tyrannosaurus rex''.〔 In 2001, a more complete juvenile tyrannosaur (nicknamed "Jane", catalogue number BMRP 2002.4.1), belonging to the same species as the original ''Nanotyrannus'' specimen, was uncovered. This discovery prompted a conference on tyrannosaurs focused on the issues of ''Nanotyrannus'' validity, held at the Burpee Museum of Natural History in 2005. Several paleontologists who had previously published opinions that ''N. lancensis'' was a valid species, including Currie and Williams, saw the discovery of "Jane" as a confirmation that ''Nanotyrannus'' was in fact a juvenile ''T. rex''.〔Currie, Henderson, Horner and Williams (2005). "On tyrannosaur teeth, tooth positions and the taxonomic status of ''Nanotyrannus lancensis''." In "The origin, systematics, and paleobiology of Tyrannosauridae", a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University.〕〔Henderson (2005). "Nano No More: The death of the pygmy tyrant." In "The origin, systematics, and paleobiology of Tyrannosauridae", a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University.〕 On the other hand, some, such as Peter Larson, continued to support the hypothesis that ''Nanotyrannus lancensis'' was a separate but closely related species.〔Larson (2005). "A case for ''Nanotyrannus''." In "The origin, systematics, and paleobiology of Tyrannosauridae", a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University.〕 In 2015, Professor Phil Manning and Dr Charlotte Brassie of Manchester University studied Jane using a LIDAR scanner, and using data and computer modelling, their reconstruction of body mass suggested that Jane had a 600 kg - 900 kg body mass, far lower than would be expected for a ''Tyrannosaurus''〔"Dino Death Match" (2015) Part of ''Jurassic Week''. National Geographic Channel (UK). 13/06/2015〕. Also in 2015, Assistant Professor Holly Woodward Ballard of Oklahoma State University used Histology to examine a thin slice of Jane's femur. Counting the rings within Jane's bone material showed that Jane was 11 years old, and bone histology suggests that Jane was still growing.〔 The actual scientific study of "Jane", set to be published by Bakker, Larson, and Currie, may help determine whether ''Nanotyrannus'' is a valid genus, whether it simply represents a juvenile ''T. rex'', or whether it is a new species of a previously identified genus of tyrannosaur. In late 2011, news reports about a 2006 discovery of a new, virtually complete ''Nanotyrannus'' specimen found along with a previously unknown ceratopsid were made.〔Switek B, ("Montana’s "Dueling Dinosaurs" ), ''blogs.smithsonianmag.com'', 10-11-2011.〕 The specimens were studied by Robert Bakker and Pete Larson on-site, who identified the ceratopsian as ''Triceratops'', although it may yet prove to be a distinct species. The ''Nanotyrannus'' specimen, nicknamed "Bloody Mary", has arms of 3 feet in length, and all of the bones in which are approximately one and a half times larger than the ''T. rex'' specimen "Sue"'s, yet the body itself is far smaller, and the skull being approximately half of Sue's length, giving a strong indicator that ''Nanotyrannus'' and ''Tyrannosaurus'' are distinct.〔 The fact that the small "Bloody Mary" specimen was found alongside such a physically mismatched opponent as a large ceratopsian has been used to suggest that ''N. lancensis'' was a pack hunter. Robert Bakker also found evidence for pack hunting in ''N.lancensis'' in the presence of some 30 ''Nanotyrannus'' teeth embedded throughout the skeleton of one ''Triceratops'' carcass.〔 Further analysis of the "Bloody Mary" specimen is currently impossible, as it remains in private hands〔 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「Nanotyrannus」の詳細全文を読む スポンサード リンク
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