Preparation sequence: Isotelus gigas (Walcott-Rust Quarry)

Updated: Feb 15

Blog has been quiet for a while, no time... However this amazing trilobite deserves a post, so here are a few preparation step by step photos of Isotelus gigas, photos and prep by A. Ž. for

But first, a few words about the history. Ordovician fossiliferous layers with trilobites near Trenton Falls, in New York (later known as the Walcott-Rust quarry) were discovered in 1860-1870 by William Rust and Charles D. Walcott. They probably became aware how amazing the preservation of these trilobites is rather quickly, and commercially excavated the layers for several years, selling specimens to collectors and institutions - and in this process discovered several species new to science. After Walcott's interests shifted and he went on to discover Burgess shale fauna, the quarry was forgotten and “lost” for more than a century, before further research started by Thomas E. Whiteley in the 90’s and later by Cooper And Skabelund. You can read more about the history of the site on the fantastic AMNH website:

Walcott-Rust excavation was carried out by hand and then rocks carefully broken down and examined for cross sections. It was laborious work, time-consuming and then followed by time-consuming preparation, but these bugs well deserve to be seen and appreciated. The preservation of these trilobites is amazing, perfectly preserved in limestone in 3D, like they are ready to crawl of the rock. In fact very similar preservation to Moroccan devonian trilobites. Very similar laborious work too, but unfortunately, not as easy to get unprepared as Moroccan material...

So, back to prep sequence... When very good preserved, these bugs can be prepared out of the hard limestone almost fully with a "needle", exoskeleton is smooth, covered with poores, not complex, but prep takes time, to avoid cracks in the exoskeleton. For preparators of Moroccan trilobites the prep process can be described as rather easy, although time-demanding; some parts, eyes especially, can be sticky and the glass like exoskeleton requires carefull approach - of course, everything depends on the preservation of each specimen and break, as always... Anyway, without further blabla:):

An example of Isotelus in a good cross section, specimen before preparation:

After both parts of limestone were glued together:

Hours later:

Almost finished, the sticky eyes needed some more cleaning up:

Other side:

Cleaned up:

The preservation of pores and terrace lines is fantastic, and even eye-lenses preserved:

And cleaned up some more:

Isotelus gigas, prepped in our lab by A.Ž.:

A few closeups, specimen whitened with Nh4Cl:

Isotelus exoskeleton structures (covered with Nh4Cl), photo&prep A.Ž.

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