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单词 Macroconch
释义

Macroconch

英语百科

Ammonoidea

An ammonite shell viewed in section, revealing the internal  chambers and septa. Large polished examples are prized for their aesthetic, as well as scientific, value.
Iridescent ancient ammonite fossil on display at the American Museum of Natural History, New York City, around 2.5 feet in diameter
Fossil shell of ammonite Placenticeras whitfieldi showing punctures caused by the bite of a mosasaur, Peabody Museum of Natural History, Yale

Ammonites (pronunciation: /ˈæmənts/) are an extinct group of marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appear during the Devonian, and the last species died out during the Cretaceous–Paleogene extinction event.

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