At first, it wasn’t thought that they were real. The name graptolite reflects this mistaken belief, translating to “written rock.” Linnaeus gave this name to the curious marks found in ancient shales and limestones. They looked like enigmatic scribblings in pencil, and he dismissed the idea that these scratches were actual fossils. But it turns out that the writing once lived.
Hundreds of millions of years ago, graptolites swam in countless numbers throughout the world’s oceans. They were not single organisms, but rather tiny colonies of individuals (called zooids) linked together in branches (called stipes). You can tell different species of graptolite apart by the number and shape of their stipes, as well as by the arrangement of the thecae, the little cup-like houses in which each zooid lives, part of a community. Graptolites evolved into a staggering variety of delicate and specialized shapes, resembling spirals, Vs, ferns, eyelashes.
Given their global distribution and diversity of form, graptolites serve as invaluable index fossils for the Paleozoic era. An index fossil is one that reliably indicates a specific timespan, ideally one as brief (geologically speaking) as possible. Because graptolites evolved distinct new forms so rapidly, the presence of any given form clearly correlates the site where it was found with a particular moment in time. They are a popular index fossil for this reason, and a typical journal article in this field is entitled, “Ground-truthing Late Ordovician climate models using the paleobiogeography of graptolites.”
Even though it’s bad form, I’ll quote Wikipedia to elaborate on ‘ground-truthing’: “Ground truth is a term used in various fields to refer to the absolute truth of something.” In some disciplines, you may not be able to access the actual, absolute truth. A ground truth, then, may be an agreed-upon standard (like a graptolite) against which the truth of other data (like the age of a rock) is measured. It is possible to have a flawed or imperfect ground truth. Generally, though, it’s the truest thing you can find.
So my reasons are thus: because truth-seeking, delicate sea creatures, close-tied communities, and writing that comes alive are all very meaningful to me, and because a tattoo pinpoints a particular moment in time, too.
I highly recommend Anka at Gristle Tattoo in Williamsburg, Brooklyn for her gorgeous work and general awesomeness.
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