graptolite
An extinct marine invertebrate from the Paleozoic era; a technical term in paleontology.
Graptolites are important as index fossils of the Paleozoic era.
Many graptolite fossils were found in this stratum.
Katakana spelling is standard for this scientific term.
Kanji spelling is rare; the word is usually written in kana.
From 筆 (fude, 'brush') + 石 (ishi, 'stone'), referring to the brush-like appearance of the fossil.