| 词汇 | ammonite |
| 释义 | ammonite noun[ C ] geology specializeduk /ˈæm.ə.naɪt/ us /ˈæm.ə.naɪt/ an extinct sea creature (= one that no longer exists) often found as a fossil (= an animal turned into rock), with a flat, spiral shell菊石（鹦鹉螺的化石） LAWRENCE LAWRY/Science Photo Library/GettyImages Palaeontology & fossils ammonoid biozone carbon dating fossil fossil record fossilization fossilize fossilized index fossil microfossil missing link palaeontologist palaeontology petrifaction petrify radiocarbon dating unfossiliferous "What's happened?" said the vicar, putting the ammonite on the loose sheets of his forth-coming sermon. The fossil ammonites found in India include at least fifteen species. They contain gigantic ammonites. ammonite | American Dictionaryammonite noun[ C ] us/ˈæm·əˌnɑɪt/ earth science an extinct (= no longer existing) sea creature often found as a fossil (= animal or plant preserved in rock) Examples of ammoniteammonite This siltstone unit lies upon a conspicuous erosion surface highlighted by angular chips of phosphatized pebbles and ammonites. The central part begins with ammonite-bearing crinoidal limestones and black pillow basalts. Cladistic techniques have been applied to many fossil groups but ammonites remain largely understudied in this way. Detailed collecting through 15 sections across the basin has facilitated a major revision of the ammonite zonation. The fauna is limited to ammonites and a species of epifaunal bivalve. This method can therefore be used to compare the morphological signal of ammonites with other physical or chemical signals. We note, however, that ammonites have not been recorded from the 1.8 m of strata below the proposed boundary level. The sudden appearance of these genera represents a major reinvasion of the basin by neocomitid ammonites. Apart from ammonites and dinoflagellates, very little other stratigraphic data is discussed in detail. Dashed ammonite-zone and bed boundaries reflect some uncertainty of their precise position in the core. Most of the ammonites studied have ribs, tubercles, keels and other ornaments. Nektonic taxa such as belemnites and ammonites dominate the fauna, with lesser bivalves and brittle stars found almost exclusively in the coarser units. No ammonites have been recorded from between -1.8 m to 0 m in the section. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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