Preparation on a rare Silurian Calymene trilobite.

Time has once again gotten away on me for a timely blog post. For those who don't know, Stormbed is a one-person company so my output (particularly these blogs), is occasionally on the slow side. Between daily posts, daily prep, fossil photography, collecting trips and website maintenance, I'm usually behind on one thing or another! For today's blog, I'll be delving deeper into my preparation process. It's not rocket science but it does require patience, specialized equipment, patience, time, patience and above all things- patience.

This blog will also be dealing with an undescribed species of trilobite so I'll be clear on something, I specialize in collection and preparation. Taxonomy and internet arguments don't hold much interest for me- what I truly enjoy is the BUGHUNT and then taking that stone and making said bug look as good as my skill set will allow. In any case we'll be looking at an extremely rare Calymene trilobite from Northern Ontario. The Silurian rocks of Ontario have a faunal spectrum very similar to the Silurian rocks of Anticosti Island in the Gulf of the St. Lawrence river in Quebec. The trilobite in question is most likely closely related to either Calymene gamachei or the famously large Dicalymene schucherti. The name Calymene means 'beautiful crescent', a reference to the bubble-like glabella on these trilobites. With well over twenty-thousand species of described trilobites and counting, there are few that bear such a close resemblance between species as the Calymenes. Typically sporting 13 segments, deep glabellar furrows and small pygidium (tail), Calymene trilobites are known from Ordovician and Silurian rocks from all over the world.

Earlier this fall I made it up to the Stormbed Quarry which is a few hours North of the city of North Bay, Ontario. With 5 days to collect it should have been a banger of a trip however, typical of this rainy 2023, I only got a day and a half of good collecting in (and even that was between rainstorms). Luckily one of the finds is the subject of this blog as well as a beautiful multi-plate of Rielaspis trilobites. For more info on this locality and the Thornloe/Earlton formations, check out my previous blog on the subject; "3 days at the Silurian pain farm".

After the 9 hour drive, it's always exciting to get on site and start crawling over the rock piles, scanning for shapes. After that, it's time to start splitting things up. My occasional collecting buddy, Mark, split down a huge limestone block which probably weighed about 200 pounds and contained the bug. Hearing the excited yelling, I scaled across the rocks faster than Sméagol in Mordor. The trilobite, in 'prone' orientation, was completely split through the middle. Despite this only being the second example of complete calymene found in the quarry, the shape of the body was instantly recognizable as a Calymene/Dicalymene WITH cheeks. Knowing you have a complete, non-molt trilobite is always a relief. That said, knowing the amount of work ahead to see what it will look like when finished is AGONY.

Calymene 'as found'. Look to the right of the hammer. What we are seeing here is the 'negative' side of the split with the main body locked in upside down. A lovely pronounced free cheek tightly attached is a beautiful sight for any who collect Calymenes.

Retrieval. Since the rock here is very fissile, hard and unpredictable, due diligence is advisable. The first thing I do is to get close with my field knife and poke around for any missing or loose shards of shell. I collect pretty much every loose flake in the vicinity of the split and tuck them into a foil packet which is then marked and put somewhere safe. A missing shard of shell can sometimes be heartbreakingly noticeable on an otherwise perfect specimen. A little bit of caution can save you from a major disappointment in the lab. Those missing shards look like the grand canyon under the microscope. After shard collection, I 'tap' in a little field glue. I usually just use the thin-set Star bond formula which has a water-like viscosity. Removing thick blobs of glue is no fun and can seriously hurt your odds of a good prep. Because low-viscosity glue behaves like water, you can use toothpicks etc to transfer small amounts of glue that soak into (and strengthen) any possible cracks BEFORE you try and cut it out. Because of the thick bedding planes here, a large Stihl (or equivalent) saw is always a good idea. I own a TS-420 model with the 14" blade which is has been an excellent piece of gear. Once the glue is dry, I grab my sharpie and mark off my cut-lines. Something I've changed in recent years is to cut clean, geometric shapes out. I bring my square ruler and try to see the final shape of the plate. Plates can always be re-shaped and re-cut at home but there is a risk every time you put that fossil to the saw. I'm not trying to write rules here or educate you, just explaining my personal process which is to cut it clean and right the first time. Once I've collected my shards, strengthened the bug with glue, marked out my cuts it's time for the saw and then into the aluminum foil.

In the lab: Now we jump ahead to the lab portion of the process! With two reasonably sized pieces cut out we can now plan the prep. This one is fairly straightforward but with the added difficulty of how hard this rock is and the patience required. Again, I'm only explaining my own process here. It's what works for me and my skillset- there's a lot of preparators out there and we all do things a bit differently. The first thing I do is to check both positive and negative under my scope for any loose or stuck parts. Right now I'm using a couple Olympus SZ30

scopes with a Barlow lens (This will increase FOV, working distance and cut down max magnification, perfect for fossil prep) and WF10X eyepieces with a 23mm FOV. Personally I find this setup effective for most jobs though getting enough light is usually difficult (I'm running at least 20k+ lumens). Once I confirm that there are no loose bits or shards trapped in the glue, I lightly abrade both positive and negative slabs with dolomite powder using my airdent machine. Doing this ensures that excess glue or loose bits of rock wont interfere with a tight fit between positive and negative. Careful examining of both pieces will also inform you of what may be missing so there's no nasty surprises. Once cleaned up, dry fit them and make absolutely sure both pieces fit together as tightly as possible. Normally I would cut out the negative section of the trilobite in a 'plug' and glue down to the positive- this makes for a LOT less work and matrix removal. Due to the brittle nature of this rock and the rarity of the specimen, I did it the hard way to mitigate the risks.

Clamp and glue: IMPORTANT! before the ol' clamp and glue part, make sure you use a ruler and mark off the location of the trilobite BEFORE. It seems obvious but I have definitely made the mistake of thinking I would remember/obvious position, cant miss it etc and it has never worked out well. Also marking off the direction the trilobite is heading will save you a headache. This also gives you a target zone- what I mean is that certain parts of the trilobite are harder (like the axials). When you're looking for the bug, you don't want to accidentally blast a hole through the soft glabella or (depending on species) some other fragile part of the process. Personally, I like to go for the axials first and work towards the head then work back down the body before carefully excavating the pleurals.

Once I've marked off the bug, dry fit, checked for gaps, it's time for clamps and glue. I clamp the pieces as close to centre/trilobite location as possible so theres no lifting on the sides. Once clamped, I slowly add StarBond thin-set cyanoacrylate to the crack between slabs. Because this glue has such a low viscosity, it easily penetrates into the slab with capillary action. Weird tip: This glue will give you the best results if it's kept in the freezer. At room temperature, eventually it'll thicken over time so make sure to have fresh stuff available. I often use more that one clamp to ensure a tight fit. Be careful on over-tightening too, it can be a disaster.

Working down. It's always a good idea to leave your clamped project overnight. 24 hours will ensure the glue is dried throughout the piece though drying times are often much sooner. Now comes the part which I find is the most stressful; locating the trilobite. Because the negative slab was left fairly thick to protect the bug, I used diamond wheels on my Dremel tool to 'grid out' the edges and make bulk matrix removal an easier process. Keeping in mind that there's a trilobite under that grid, using a large scribe is so much easier on hard rock with these grids. I use a similar technique on Moroccan trilobites. I've been using a ME9100 for bulk removal though I must say, it's not the most reliable tool in my arsenal. Hopefully in 2024 I'll be upgrading to the excellent German scribe HW7 or perhaps try some of the Belaur products which have been recommended to me by my colleagues. Using a combination of scribe and blaster, I rotate between the tools until I locate shell. I blast down at a pressure that will move matrix (But not punch through shell) in an exploratory hole, then scribe the surrounding area to make a deeper hole until I find my bug. Once located, the stress abated, we can really plan to cut deeper with the wheels and remove the excess edges of matrix. Basically, I'm going to remove every damn thing from the negative slab that isn't trilobite. I should also mention that this rock is so hard that dolomite powder is about as effective as harsh language on this rock (believe me I've tried all the swears) so I mix in about 10-15% Aluminum oxide powder for a little more firepower. Care should always be used when preparing with Al2O3, the shape of its molecule is very harsh and can absolutely melt trilobites as well as eating the guts of your blaster rig.

Well hello there! Houston we have bugshell. I'm a little closer to the glabella than I wanted to be but this was a good result regardless. It's always exciting to see the dorsal side of a buried bug for the first time, by any animal in hundreds of millions of years. At the very least, this particular primate always gets a thrill.

Combining Dremel, scribe and blaster, we have uncovered from the head to the tail. With fissile rock like this, be wary of missing shards in the base which can make pockets which will not only 'grab' onto your scribe but vibrate and potentially cause damage to the trilobite. At this point we are at around 4-5 hours of prep time- you guessed it- patience is key.

Slow going but progress is good.

Final touches. We're getting close now with the bulk prep. Note the micro fossils accumulated in the Glabellar furrows and above the axial line. These are stubborn and must be removed carefully at the detail stage. Once all of the 'overburden' matrix has been removed, I usually do my landscaping before I start the detailed phase of prep with smaller blaster tips and higher magnification. I usually do this because I'll often tweak the landscaping several times until I'm happy with it. More time under the scope at the 'details' phase lets me look for weak spots in the overall aesthetic of the piece.

The finished piece. A beautiful crescent indeed! Though the Earlton/Thornloe trilobites are not the showiest bugs for contrast, they are still wonderfully preserved and extraordinarily rare trilobites from a poorly studied area of Northern Ontario, Canada. Thanks so much for reading my blog on the prep of this beautiful 5.3cm, 444 million year old bug! As always, reach out with your questions on prep and/or available pieces. Merry Xmas/Happy Holidays, A Happy New Year and stay tuned for more content in 2024!

Mike Meacher - Stormbed Paleontological ©2023