graptolite
/ˈgræptəlaɪt/noun
1- a fossil marine invertebrate animal of the Palaeozoic era, forming mainly planktonic colonies and believed to be related to the pterobranchs笔石。
1.1
- Class Graptolithina, phylum Hemichordata.笔石纲, 半索动物门。
词源
mid 19th cent.: from Greek graptos 'marked with letters' + -LITE： so named because of the impressions left on hard shales, resembling markings with a slate pencil.