With the arrival of six unprepared Russian trilobites, I got to work and banged out three. With the exception of one that is partially enrolled, the other five are prone. There are no Asaphus lepidurus in the lot as I've prepped enough of those, and they are effectively the cockroaches of the St Petersburg fauna -- so much so that they function as index fossils. So let's kick it off with an Asaphus latus, the wide-load of Russian asaphids: The first step is to scribe bulk matrix getting as close as one can to the shell without dinging the shell. Fortunately, the matrix has generally good separation if there isn't too much calcitic crust. At this stage, the scribing is finished after an hour, and I've already started in on abrasion. Working around the eyes should be done alternating between scribe and abrasion. This bug had some cracks running through it, so I didn't reduce the slab by too much. There are a few minor flaws intrinsic to its deposition and preservation, but on the whole it is almost flawless. Total run time was about 3.5 hours, which is not bad (thanks to some much better tools). There is not one scribe ding on the shell. Although I didn't photograph them, the holochroal eyes are perfect, showing the fine details of the tiny lenses. This is the taller-eyed Asaphus punctatus. This one was a bit trickier on account of some calcitic crust on the shell. The outer rim of the pygidium is also slightly pitted. Scribing/abrasion alternation is required when dealing with trilobites with taller eye stalks so as not to accidentally scribe through them, or pop them off. Once the main bulk scribing was done, and the slab reduced so that the cephalon pokes a bit over the edge (I was tempted to check for a hypostome), time for straight dolomite abrasion. And, done. The cephalon is about to separate on the right side, indicative of likely being caught in the process of ecdysis. The cephalon is also slightly crushed, as evidenced by the compression cracks. Running time on this one was about 3 hours. And now for something slightly different: the mud-loving Illaenus oblongatus. These take a slightly different approach than their asaphid cousins on account of some thin-skinned areas, particularly the thorax and the anterior face of the cephalon. As can be seen, this one has problems: mineral leeching of the shell, some pitting. It was also held in place at one part by a mysterious Russian glue that is resistant to acetone and takes a hard push with abrasion. The trick here is to be delicate with abrasion on the thinner areas. At this stage, only the eyes and the palpebral lobes are visible, but these cephalons run deep. Only took me a couple of hours. The unwelcome surprise was that the left side was missing its pleural tips, and I can assure you that it wasn't me being hasty with the scribe either, as I had left a good sized hump over that area which I abraded down. I am thinking it was an injury sustained just prior to death. Another unwelcome surprise was calcitic crystals on the rim of the pygidium that had eaten/pitted that area.
Still, a healthy 6ish cm prone illaenid is nothing to turn one's nose up despite its character flaws. So that's half of the new lot done. I'm fairly pleased with the results. Apart from improvement in tools and techniques, it is also usually the case that buying unprepared fossils will mostly be specimens that have too many problems (or else why would these preparators sell them in the first place as opposed to do it themselves?). I was actually pleased that any of the defects that saw them consigned to be sold unprepared were relatively minor. Play time at the bench will have to take a brief hiatus as I grade a mountain of papers, but I hope to get to the other half sometime next week. Up next are an Asaphus cornutus x 2, and a partially enrolling/arched Asaphus latus. Comments are closed.
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Kane Faucher
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February 2024
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