graptolite

/grap-tuh-lahyt/US // ˈgræp təˌlaɪt //UK // (ˈɡræptəˌlaɪt) //

斑岩,斑鸠石,纹石,凹凸纹石

Definitions

n.名词 noun

1
- : any colonial animal of the extinct class Graptolithina, most common in the Ordovician and Silurian Periods, thought to be related to the pterobranchs.

The strata consist of greywackes, flags and shales with seams and zones of graptolite shale which yield fossils sparingly.
A typical graptolite consists of an axis bearing a series of tooth-like projections, like a saw.
The genus Bryograptus, a many-branched graptolite, also appears to characterise this fauna.
These consist of greywackes, flags and shales with bands of dark graptolite shales, the finer sediments being often well cleaved.