File:Anomalocaris canadensis grasping claw, Burgess Shale.jpg
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[编辑]描述Anomalocaris canadensis grasping claw, Burgess Shale.jpg |
Anomalocaris canadensis Whiteaves, 1892 grasping claw (~8.5 cm long), preserved as a carbonized film in slightly metamorphosed shale from the Middle Cambrian-aged Burgess Shale of southwestern Canada (YPM 35138, Yale University’s Peabody Museum, New Haven, Connecticut, USA). The Middle Cambrian-aged Burgess Shale is the most famous fossil deposit on Earth. It is located near the town of Field in Yoho National Park, southeastern British Columbia, western Canada. The deposit is famous for its spectacular soft-bodied preservation - the organisms have had their appendages & internal organs preserved. Many tens of thousands of fossils have been collected from the Burgess Shale Formation over the last century. Including known, but unnamed species, and excluding known or demonstrable junior synonyms, the Burgess Shale biota totals at least ~280 species. Many claim that Charles Walcott discovered the Burgess Shale Lagerstätte (as soft-bodied fossil deposits are called by paleontologists) in 1909. However, it was actually discovered in 1886 or 1888 by Richard McConnell, based on anomalocarid appendage material from Mt. Stephen, in the Campsite Cliff Member of the Burgess Shale Formation. The main collecting localities have been two quarries (Walcott Quarry & Raymond Quarry) on the western side of the ridge connecting Mt. Field and Wapta Mountain a little north-northeast of Field. Numerous other smaller localities have been identified in the same area & for many, many kilometers to the south. Collecting at the Burgess Shale was most intense in 1910-1917 (Charles Walcott), 1925-1930 (Harvard’s Museum of Comparative Zoology), 1966-1967 (Geological Survey of Canada), and 1975-2000s (Royal Ontario Museum). Some of the most celebrated problematic fossil organisms from the Burgess Shale are the anomalocarids, the namesake of which is Anomalocaris canadensis Whiteaves, 1892. The genus name “Anomalocaris” means “strange shrimp”, which is ironically appropriate, because the name was given to fossil remains identified as shrimp bodies. But, anomalocarids are anything but shrimp. These creatures had medium-sized to large bodies (extrapolated up to ~3 meters long) with a head having a pair of grasping claws & short-stalked eyes & a pineapple ring-shaped mouth, plus a body with two lateral rows of swimming flaps. The first anomalocarid fossils (isolated grasping claws) were discovered in the 1880s from British Columbia’s Burgess Shale Formation. They were identified as shrimp bodies lacking heads (see this photo). In general, paleontologists didn’t recognize that these Anomalocaris fossils represented parts of a much larger organism. The true nature of the complete Anomalocaris organism wasn’t realized until very rare complete specimens were excavated from Burgess Shale quarries by the Royal Ontario Museum. The "headless shrimp" fossils turned out to be grasping claws at the head end of a large animal that could not be classified with any traditional arthropod group. New high-level taxa have been created to accommodate it (see Collins, 1996, Journal of Paleontology 70: 280-293). Classification: Arthropoda, Dinocarida, Radiodonta, Anomalocaridae Stratigraphy: Walcott Quarry Member, Burgess Shale Formation, Ptychagnostus praecurrens Interval-zone, lower Marjuman Stage, middle Middle Cambrian. Locality: Walcott Quarry, western side of ridge between Mt. Field & Wapta Mountain, north-northeast of the town of Field, southeastern British Columbia, southwestern Canada. |
日期 | |
来源 | Anomalocaris canadensis grasping claw (Burgess Shale Formation, Middle Cambrian; Walcott Quarry, above Field, British Columbia, Canada) |
作者 | James St. John |
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[编辑]这幅图片原始出处为Flickr的https://www.flickr.com/photos/47445767@N05/15113335009 ,作者为jsj1771 。经机器人FlickreviewR在2014年9月21日审查后确定为采用cc-by-2.0的协议授权使用。 |
2014年9月21日
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宽度 | 1,797 px |
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高度 | 1,198 px |
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压缩方案 | 未压缩 |
像素构成 | RGB |
方向 | 正常 |
色彩组分数 | 3 |
水平分辨率 | 300 dpi |
垂直分辨率 | 300 dpi |
数据排布 | 大块格式 |
使用软件 | Adobe Photoshop CS2 Macintosh |
文件修改日期时间 | 2014年9月20日 (六) 14:49 |
色彩空间 | 未标定 |
图像宽度 | 1,797 px |
图像高度 | 1,198 px |
数字化日期时间 | 2006年11月27日 (一) 09:10 |
元数据最后修改日期 | 2014年9月20日 (六) 10:49 |
IIM版本 | 2 |