File:Nanotyrannus_lancensis_skull.jpg
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摘要
描述Nanotyrannus lancensis skull.jpg |
Nanotyrannus lancensis (Gilmore, 1946) theropod dinosaur skull (60 cm long) from the Cretaceous of Montana, USA (public display, CMNH 5741, Cleveland Museum of Natural History, Cleveland, Ohio, USA). A remarkable “pygmy” tyrannosaurid dinosaur was proposed in 1988 by Bob Bakker, Philip Currie, and Michael Williams on the basis of a well-preserved skull housed at the Cleveland Museum of Natural History (specimen CMNH 5741). The skull of Nanotyrannus lancensis (Gilmore, 1946) was first discovered in 1942 in Carter County, southeastern Montana, USA, by a team from the Cleveland Museum of Natural History. Nanotyrannus was found in the Hell Creek Formation of late Maastrichtian age (near-latest Late Cretaceous - 67 million years). The original published description placed this species in the theropod genus Gorgosaurus, which is now a junior synonym of Tyrannosaurus. Re-examination (including CT-scanning) of this skull by dinosaurologist Bob Bakker in 1987 and 1988 resulted in taxonomic reassignment to a new genus altogether - Nanotyrannus (“pygmy tyrant”). For a while, the new genus was being referred to as “Clevelanotyrannus”! The skull is small for a tyrannosaurid dinosaur (60 centimeters long), but paleontologists have noted the well developed ossification of the skull (the head bones are tightly sutured), which is widely perceived to be a feature diagnostic of an adult individual. Other perceived adult aspects of the skull convinced Bakker that this was not a juvenile specimen of an otherwise large theropod dinosaur, but an adult of a miniature theropod (extrapolated to be about 5 meters total body length). If correctly interpreted, Nanotyrannus represents a clade of tyrannosaurid theropods that underwent evolutionary dwarfism very late in the history of dinosaurs. This biologic validity of Nanotyrannus has not been universally accepted. Gregory Paul (1988) was inclined to assign the species to Albertosaurus. Thomas Carr (1999) perceived that Nanotyrannus has morphologic features consistent with juvenile Albertosaurus. Philip Currie (2003) suggested that Nanotyrannus possibly represents an early ontogenetic stage (juvenile) of Tarbosaurus or Tyrannosaurus. A re-examination of the skull by CT-scanning in the 2000s has shown that the skull morphology is not consistent with it being a juvenile individual (see Witmer & Ridgeley, 2010). Theropod were small to large, bipedal dinosaurs. Almost all known members of the group were carnivorous (predators and/or scavengers). They represent the ancestral group to the birds, and some theropods are known to have had feathers. Some of the most well known dinosaurs to the general public are theropods, such as Tyrannosaurus, Allosaurus, and Spinosaurus. Mostly synthesized from info. provided by: Bakker, R.T., M. Williams & P.J. Currie. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1-30. Bakker, R.T. 1992. Inside the head of a tiny T. rex. Discover 13: 58-69. Carr, T.D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria: Coelurosauria). Journal of Vertebrate Paleontology 19: 497-520. Cleveland Museum of Natural History Currie, P.J. 2003. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North Amercia and Asia. Canadian Journal of Earth Sciences 40: 661-665. Paul, G.S. 1988. Predatory Dinosaurs of the World. New York. Simon & Schuster. 464 pp. Witmer, L.M. & R.C. Ridgely. 2010. The Cleveland tyrannosaur skull (Nanotyrannus or Tyrannosaurus): new findings based on CT scanning, with special reference to the braincase. Kirtlandia 57: 61-81. |
日期 | |
来源 | Nanotyrannus lancensis theropod dinosaur (Hell Creek Formation, Late Cretaceous; Carter County, southeastern Montana, USA) 2 |
作者 | James St. John |
许可协议
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这幅图片原始出处为Flickr的https://www.flickr.com/photos/47445767@N05/15375756215 ,作者为jsj1771 。经机器人FlickreviewR在2014年9月29日审查后确定为采用cc-by-2.0的协议授权使用。 |
2014年9月29日
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某些值没有维基数据项目
22 7 2006
曝光时间 简体中文(已转写)
0.01666666666666666666 秒
4.5
46 毫米
image/jpeg
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当前 | 2014年9月29日 (一) 16:56 | ![]() | 2,699 × 1,589(1.44 MB) | Cropbot | upload cropped version, operated by User:FunkMonk. Summary: cropped |
2014年9月29日 (一) 12:40 | ![]() | 2,722 × 1,651(1.13 MB) | FunkMonk | Transferred from Flickr via Flickr2commons |
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相机制造商 | NIKON CORPORATION |
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相机型号 | NIKON D70s |
曝光时间 | 1/60秒(0.016666666666667) |
光圈值 | f/4.5 |
数据生成日期时间 | 2006年7月22日 (六) 14:40 |
镜头焦距 | 46毫米 |
方向 | 正常 |
水平分辨率 | 300 dpi |
垂直分辨率 | 300 dpi |
使用软件 | Adobe Photoshop CS2 Macintosh |
文件修改日期时间 | 2014年9月27日 (六) 23:49 |
YCbCr位置 | 重叠 |
曝光程序 | 未定义 |
Exif版本 | 2.21 |
数字化日期时间 | 2006年7月22日 (六) 14:40 |
每个色彩组分意义 |
|
图像压缩模式 | 4 |
APEX曝光补偿 | 0 |
最大光圈 | 4.3 APEX(f/4.44) |
测光模式 | 多区 |
光源 | 未知 |
闪光灯 | 闪光灯点亮、检测到闪光灯返回光、自动模式 |
修改时间厘秒数 | 90 |
数据生成时间厘秒数 | 90 |
数字化时间厘秒数 | 90 |
支持的Flashpix版本 | 1 |
色彩空间 | sRGB |
感光方法 | 单芯片彩色区域传感器 |
文件来源 | 数码相机 |
场景类型 | 直接拍摄的图像 |
自订图像处理 | 普通处理 |
曝光模式 | 自动曝光 |
白平衡 | 自动白平衡 |
数字变焦比率 | 1 |
35毫米胶片焦距 | 69毫米 |
场景拍摄类型 | 标准 |
场景控制 | 无 |
对比度 | 低 |
饱和度 | 标准 |
锐度 | 标准 |
拍摄对象距离范围 | 未知 |
支持的Flashpix版本 | 1 |
图像宽度 | 2,722 px |
图像高度 | 1,651 px |
元数据最后修改日期 | 2014年9月27日 (六) 19:49 |