Reference work entry
Ammonite obtained its Chinese name Chrysanthemum Stone because it looks like a blooming chrysanthemum. There are many species, and they vary greatly in size from a few centimetres to more than 10 cm. The largest is larger than a cooking pan. Ammonites were marine invertebrates that lived 400 million to 65 million years ago. Due to their rapid evolution, they had remarkable characteristics and were widely distributed. Ammonites are the most effective index fossils for the determination and comparison of rock strata, and they have facilitated the demarcation of many Jurassic and Cretaceous marine facies. The longitudinal section of an ammonite looks like a beautiful spiral with a colour like amber (Fig. 14).
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