当恐龙称霸的时期,在海洋中生活着一类奇特的微体生物——颗石藻。颗石藻是海洋中重要的单细胞浮游植物类群,通常具有碳酸钙的外壳(称之为颗石粒,下文有详解),藻体整体多为椭球形,少数物种呈现梭形等其他形态,大小多介于2～20μm,少数大于20μm;但碳酸钙外壳具有多种形态,这也是形态学鉴定的主要依据。现已知最早的颗石藻化石大约出现在距今2.2亿年左右,自那时起,颗石藻适应了当时的海洋环境,通过进化产生了由体内向体外 During the dominion of the dinosaurs, a strange kind of micro-organism, coccolith, lives in the sea. Coccolith is an important group of single-celled phytoplankton in the oceans. It usually has the shell of calcium carbonate (it is called granulite, which will be explained in detail below). Most of the algae are ellipsoidal in shape, while others are fusiform and other forms. The size of more than 2 ~ 20μm, a few more than 20μm; but calcium carbonate shell has a variety of forms, which is the main basis for morphological identification. It is known that the earliest coccolith fossils appeared about 220 million years ago. Since then, coccoliths have adapted to the marine environment at that time and have evolved from in vivo to in vitro