Tommotian and Burgess Shale formations give clues about Precambrian evolution.
早间,Tommotian和伯吉斯页岩化石群为前寒武纪进化提供了线索。
单词 | Tommotian |
释义 |
Tommotian
原声例句
7天搞定托福单词 Tommotian and Burgess Shale formations give clues about Precambrian evolution. 早间,Tommotian和伯吉斯页岩化石群为前寒武纪进化提供了线索。
英语百科
Cambrian Stage 2(重定向自Tommotian)
Key events in the Cambrian view • discuss • -550 — – -540 — – -530 — – -520 — – -510 — – -500 — – -490 — – Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary. Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian series. It lies on top of the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Both the upper and lower boundary have not been clearly defined yet by the International Commission on Stratigraphy. Proposals for the lower boundary are the appearance of Small Shelly Fossils, an archaeocyathid species or the mollusc Watsonella crosbyi around ~529 million years ago. The proposed upper boundary might be the first appearance of trilobites around ~521 million years ago. |
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