跳转到内容

File:Brooksella alternata (fossil sponge) (Cambrian, Alabama, USA).jpg

页面内容不支持其他语言。
这个文件来自维基共享资源
维基百科,自由的百科全书

原始文件 (1,622 × 1,276像素,文件大小:1.52 MB,MIME类型:image/jpeg


摘要

描述
English: Brooksella alternata Walcott, 1896 - fossil sponge from the Cambrian of Alabama, USA.

“Star cobbles” are hard, three-dimensional, multilobate siliceous concretions weathered out from shales of the Conasauga Formation (Middle Cambrian) in the Coosa River Valley of Alabama & Georgia. Most are three to six centimeters in diameter (but ranging from one to ten centimeters). Star cobbles were given scientific names by Charles Walcott in 1896: Brooksella alternata, Brooksella confusa, and Laotira cambria. What star cobbles represented has been debated in the paleontological literature ever since. Walcott called them jellyfish (Phylum Cnidaria), but most modern workers hold that they are trace fossils.

A restudy of Conasauga star cobbles has concluded that these structures are body fossils, not burrows, and that Walcott’s three species belong to one highly variable species, called Brooksella alternata.

Brooksella specimens, as seen in cross sections, have no backfills, so they are not burrow fillings. They are always preserved in silica, and have a simple ellipsoidal construction with radial lobes. They vary in shape and lobe number, but they often have a central depression, and the lobes often terminate in visible openings. Most telling, sponge spicules are present on the surfaces of some specimens (even Walcott saw these, but concluded they weren’t part of Brooksella itself).

Brooksella alternata is now considered to represent a hexactinellid sponge. The central depression is inferred to be the osculum. Hexactinellids make their skeletons with siliceous spicules, and rapid diagenesis of a siliceous sponge skeleton is a great way to make three-dimensionally preserved siliceous concretions. So, Brooksella isn’t a trace fossil - it’s a sponge!

The above info. is synthesized from Ciampaglio et al. (2005, 2006), Ciampaglio & Babcock (2006), and from info. provided by Loren Babcock (pers. comm.).


References Cited

Ciampaglio, C.N., L.E. Babcock, C.L. Wellman, A.R. York, & H.K. Brunswick. 2006. Phylogenetic affinities and taphonomy of Brooksella from the Cambrian of Georgia and Alabama, USA. Palaeoworld 15: 256-265.

Ciampaglio, C.N., C. Wellman, H. Brunswick, A. York & L.E. Babcock. 2005. Reinterpretation of Brooksella from the Conasauga Formation (Cambrian) of Georgia and Alabama, USA. in The Fourth International Symposium on the Cambrian System and the Tenth Field Conference of the Cambrian Stage Subdivision Working Group, Nanjing, August 18-24, 2005, abstracts and short papers. Acta Micropalaeontologica Sinica 22(Supplement): 21-23.

Ciampaglio, C.N. & L.E. Babcock. 2006. Reinterpretation of Brooksella from the Conasauga Formation (Cambrian) of Georgia and Alabama, USA. Geological Society of America Abstracts with Programs 38(3): 4-5.
日期
来源 https://www.flickr.com/photos/47445767@N05/33763805144/
作者 James St. John

许可协议

w:zh:知识共享
署名
本文件采用知识共享署名 2.0 通用许可协议授权。
您可以自由地:
  • 共享 – 复制、发行并传播本作品
  • 修改 – 改编作品
惟须遵守下列条件:
  • 署名 – 您必须对作品进行署名,提供授权条款的链接,并说明是否对原始内容进行了更改。您可以用任何合理的方式来署名,但不得以任何方式表明许可人认可您或您的使用。
这幅图片原始出处为Flickr的https://flickr.com/photos/47445767@N05/33763805144 ,作者为James St. John 。经机器人FlickreviewR 2在2020年1月16日审查后确定为采用cc-by-2.0的协议授权使用。

2020年1月16日

说明

添加一行文字以描述该文件所表现的内容

此文件中描述的项目

描绘内容

创作作者 简体中文(已转写)

某些值没有维基数据项目

Flickr用户账户 简体中文(已转写):​47445767@N05
作者姓名字符串 简体中文(已转写):​James St. John

刊载处 简体中文(已转写)

出版日期:​12 5 2017

版权状态 简体中文(已转写)

版权所有 简体中文(已转写)

知识共享署名2.0通用 简体中文(已转写)

摄影器材 简体中文(已转写)

曝光时间 简体中文(已转写)

0.01666666666666666666

焦距比数 简体中文(已转写)

13

焦距 简体中文(已转写)

14.303 毫米

ISO速度 简体中文(已转写)

80

媒体类型 简体中文(已转写)

image/jpeg

文件来源 简体中文(已转写)

校验和 简体中文(已转写)

d055a5a8c8193bec599ce3d7ce2b512eaa6d4bac

断定方法:​SHA-1 简体中文(已转写)

数据大小 简体中文(已转写)

1,592,376 字节

1,276 像素

1,622 像素

文件历史

点击某个日期/时间查看对应时刻的文件。

日期/时间缩⁠略⁠图大小用户备注
当前2020年1月16日 (四) 18:242020年1月16日 (四) 18:24版本的缩略图1,622 × 1,276(1.52 MB)Ser Amantio di NicolaoUser created page with UploadWizard

以下页面使用本文件:

全域文件用途

以下其他wiki使用此文件:

元数据