Before 2018 runs out, a trip to the lab to prepare this semi-prone Asaphus lepidurus, the more common asaphid found in the St Petersburg, Russia quarries. Also, a new trilobite addition.
This is what it looked like before starting. The pleural orientation makes it clear that the cephalon will be projecting downward as this bug was buried in the process of enrolment. There is some damage to the final pleural segment before the pygidium. The initial challenge was getting rid of the tall stack of matrix on top of the bug using only my ARO clone with factory tip.
The GIF above shows the process after four hours of scribing and abrading. You know those preps of Russian trilobites with the soft and easy matrix due to marl content, the stuff that comes off like butter? -- Yeah, this isn't one of those. Instead, the matrix is hard with calcite crust. It is the kind of stuff that you can't risk getting too close with the scribe for fear of dinging the bug (or drilling through!), and the stuff that laughs at the air eraser even cranked up to 75 PSI. Even pin vise pricking is not able to gain enough purchase to separate matrix from shell. I'm going to have to risk approaching it blind from the anterior side in the hopes that I can locate the cephalon, working my way out and eventually freeing the left side pleurae.
The orientation is not the easiest to work with. Being semi-prone means the pleural segments tend to bunch together and are a bit more fragile... One misstep means losing shell pieces. By contrast, the axial rings are stretched out to their maximum convex flex, and that can lead to other problems such as shell thinness.
Four hours became eight hours. Eight became seventeen. The matrix was sticky and pretty much immune to dolomite abrasion. So it was the delicate and less than ideal process of using the vibrating scribe tip to "kiss" the matrix to cause it to flake off, and some matrix shaping to level down the bug's contours as well as expose the cephalon. The latter took a very long time. You can see the scribe dings in this image, but those are easy enough to fix. Now comes the finicky job of removing all the hard grit between the segments.
Success! The stubborn matrix grit is gone. The only disappointment is that this one seems to be missing the lowermost left pleural segment just anterior to the pygidium. I had been careful to level down slowly, so I didn't accidentally scribe it off; I think this is just moult-related damage, and that is made more likely by the slight misalignment of the pygidium in relation to the thorax. It happens!
Also missing a wee bit from its left eye, but on the whole a half-decent prep.
This delightful diminutive phacopid had come in the mail. From what I read, it was collected about 50 years ago from the classic "trilobite fields." Gerolstein, Eifel mountains in Germany, Ahrdorf Formation, Flesten Member. I'm told this site is no longer available for collecting, so makes this trilobite extra special. It measures just about 1 cm across the transverse axis.
While moving some spare rock from the living room to the basement where I keep my spoils, spare parts, and fossil graveyard, I decided to break open this big block I kept from my recent trip to Bowmanville. I managed to expose a bit more of this Isotelus fragment. Six out of the eight thoracic segments are visible and part of the pygidium. Had this monster been complete, it would have measured about 28 cm in dorso-saggital length! Apart from the rarity in finding such extra large isotelines, that is made more so by the fact that the very largest ones rarely preserve well being subject to more exposure, crush damage, etc. It is for that reason Dave Rudkin's team's find of that Iostelus rex in 2002/3 was such a coup (72 cm in length -- the biggest trilobite on record!). It is a bit tougher to make out the species on this one, but I'd wager this is likely an Isotelus latus. Now to wait until May to find a complete one!
But let me sneak in just one last prep before wrapping up the year. This is a
Flexicalymene croneisi that Deb found in Bowmanville in October, and I've been meaning to clean this one up. Pictured to the left is after I've done some preliminary work, and on the right is the complete deal. One hour prep. The pictures don't do it justice (it's still dusty and has some dolomite dust in the cracks, and the iPad is not the greatest for macro shots), but I'll take a better picture before putting it in the trilobite gallery.
There are collecting locations that I'm not likely to get to in the near future, and as much as I'd love to fancy myself wealthy enough to just buy up every great Russian Ordovician bug, sometimes one has to settle for the discards.
Russian preparators who eke out a living collecting and preparing trilobites are not too different than the preparators who do the same thing here: there are those (far too many) finds that are simply not worth the time and effort for whatever reason. It could be a common bug that has too much compaction damage, bad mineralization stains, too many missing parts, or anything else that might result in producing a trilobite that is far less than A-grade for sale. Buyers generally expect perfection, after all, or something close to it. So into the chuck-it bucket it goes. I have my own "graveyard" of partials, botched prep attempts, and stuff far too common yet complicated to be worth preparing unless I had nothing else in the queue.
So this is the chuck-pile bug in question. Not quite complete junk, but pretty close. It was likely found busted and glued together in the field, which is a fairly common scenario when collecting from these layers. For every nice, full (sometimes floor polish enhanced) Asaphus sp. one sees for sale, there were likely hundreds of busted up partials (some of which get recycled as grafting material). This trilobite has a lot of problems beyond the fractures tentatively held together with glue: crush damage, missing shell bits, and serious mineralization discolouration that makes it appear mottled and less than pristine sale quality. But I need the practice!
I've never prepared an illaenid before, and there are always a few "firsts" I encounter while preparing given that I haven't been doing it for that long. Each prep is a learning experience, and making serious mistakes is part of it... But so is recognizing that each prep is different, even when dealing with the same species and matrix. You try different approaches and techniques, sometimes using a wide range of tools suited just for that particular job.
So, let's have at it.
The first step was to do the scribe work, but not before consulting numerous images of this species from different angles to give me a reasonable idea of what to expect while my scribe flies blind. My scribe sailed through this matrix! By contrast, the previous prep of an Asaphus lepidurus was a dismal failure as the matrix was a dense, calcitic mess that even 75 PSI dolomite wouldn't touch unless I wanted to eat through several canisters of the stuff.
The unique aspect about this genus is that the bulbous cephalon seems to go on forever. This was where I stopped the night before, and there was still a lot more matrix to remove. When they preserve in this kind of almost semi-prone state, it is customary to just blitz off the the anterior side of the matrix, which gives this burrowing bug the appearance of "hanging over" the side. This is all scribe work: I just needed to "kiss" it with the tip and the vibration would knock off the matrix without me risking hitting the shell with the scribe tip.
And this was where I had to call it a night... Not just because I didn't want to run the air compressor beyond 10 pm and be a loud nuisance, but on account of the other result of such a soft and yielding matrix is that fractures emerge that run deep and threaten to wreck the trilobite. Pictured here is my stabilizing some vibration-made cracks by wicking some cyanoacrylate. A good ending point for the day to let it cure and get back at it in the morning.
As soon as my missus went to work, I was firing up the compressor for round two. At this point, the scribing work is pretty much done as far as I'm willing to risk it; what remains are some delicate areas that need to be air abraded. I do alternate between scribing and some air dent to test certain spots, but I'm a task-switcher by nature. The tricky spots are going to be the eyes and the genal spines.
It isn't a true prep session unless you experience a minor catastrophe (at least that is the norm for my inexperienced self!). The very thin-shelled underside of the cephalon didn't quite dig my air abrasion action, and so some shell bits went flying. I retrieved a few pieces, which is not easy to do in a dust layer in the blast chamber (or in the shop vac bag). And I don't exactly have those tiny fingers adept at threading needles. I reattached a few of the pieces I found, but some of them were lost forever. It could have been much worse, and I managed to fill in the much bigger "bald spot" with the pieces I could glue back on. This is a discarded bug anyway, and not a presentation to the Queen.
Air abrasion work reveals the eyes and frees out the gunk between the pleurae and the genals. I've moistened it with some oil to better detect other areas I might have missed.
Yes, I am such a prep noob. I will, however, take immense pride in how I managed to free up that genal spine (which had a crack in it, no less) to be my first "flying genal spine." For those who do not prep, this may seem very easy, but it is fraught with a lot of nervousness and care to ensure not blasting the spine off as a sacrifice to the hungry shop vac!
And this is where we are. I also sanded down the matrix (decided to leave a bit for aesthetic reasons). There is some cruddy glue stuff on the left pygidium that needs an acetone bath (abrasion is too risky at that section), but otherwise not bad at all for preparing what had been consigned to being a junk bug. I learned a lot, and ended up cussing a lot less while doing this one. To me this is a prep triumph.
Made a trip to the post office to pick up a backlog of packages that couldn't be delivered at the door, and it was a lovely little bonanza of bugs.
Although a bit beat-up and sticky, this will be added to my winter preparation queue. This Ordovician corynexochid is Illaenus sinuatus, a new species for the collection. The cephalons on these kinds of burrowing bugs tend to be fairly robust, so there is considerable matrix to be removed. I'll post the complete results once I get this in the lab.
Another Ordovician trilobite, the phacopid Pliomera fischeri, from Kinnekulle, Sweden. Trilobites from the Swedish part of Baltoscandia do not tend to preserve as well, and can come out fairly weathered.
From Haellekis, Sweden, an enrolled Ordovician phacopid, Nileus armadillo.
Although I already have two other examples of this species, a small and enrolled Asaphus kowalewskii will nicely complement the Russian asaphid display.
Top prize for this bug bonanza would go to this lower Devonian Moroccan phacopid, Wenndorfia planus. Nicely enrolled, and uniquely prepared in a tilted pedestaled fashion to show off its "assets," this trilobite was reassigned by Sandford (2005) to Wenndorfia from the species Parahomalanotus... which in itself was possibly mistakenly elevated to genus status. For those interested in some of the twitchy taxonomic tango see:
Sandford, A.C. (2005)
Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae).
Memoirs of the National Museum Victoria, 62(1):1-66
Basse, M., & Franke, C. (2006)
Marine Faunen aus dem frühen Unteremsium (Unterdevon) des Givonne-Oesling-Antiklinoriums (Luxemburg).
Chatterton, B.D.E., Fortey, R.A., Brett, K.D., Gibb, S.L, & McKellar, R.C. (2006)
Trilobites from the upper Lower to Middle Devonian Timrhanrhart Formation, Jbel Gara et Zguilma, southern Morocco.
Palaeontographica Canadiana, 25:1-177
A number of trilobites came in the mail, with several more waiting at the post office and some in transit. First up is a Paralejurus dormitzeri
This fairly common Devonian corynexochid from Morocco does appear fairly often for sale, but a lot of them are the victims of quick and brutal preparation. This one has very good quality preparation, with some minor restoration on the lower right pygidium. Finely detailed with the eye lenses, terraced growth lines, and pedestaled to show the cephalic doublure. Only a few scribe dings, and measures close to 80 mm.
A cute and small Asaphus kowalewskii. Although I already have an example of one (semi-prone), this young holaspid stage specimen was too adorable to pass up. Some slight compaction between the third and fourth axial ring, but virtually no restoration of this stubby-eyed example of the species.
Hooray! Another winter prep project to keep from going bonkers from fossil hunting withdrawal. This is a relatively small semi-prone Asaphus lepidurus.
Until tomorrow when a few more trilobites join the collection...
Recently returned from two weeks in Jamaica, and particularly in Ocho Rios (St Ann's Parish). The primary purpose of the trip was undoubtedly much-needed R&R after a hectic semester, so swimming in the ocean, drinks by the pool, and the usual laying about dominated our time there. Still, the lure of fossils is always strong.
About 75% of Jamaica's rocks are limestones dating back to the late Mesozoic and Cenozoic. The formation of Jamaica as it stands above water today was the result of successive volcanism. Today, it is surrounded by a diverse coral reef marine ecosystem, and has some mountainous peaks (primarily Blue Mountain, the base of which we were staying). The limestones themselves are almost entirely dominated by coral fossils, with some gastropods in the mix. The limestone is quarried from many areas and used extensively for local building needs.
When these appear as large blocks sitting around, closer inspection reveals that much of the rock is fossil coral. Pictured here are some examples, including a scleractinian coral colony.
Sadly, despite some efforts, I could not arrange to go off property to inspect some larger, natural exposures. Some exposed beds at larger quarrying sites or roadcuts rise to over 200 metres.
Pictured here are just a few of the shorter roadcuts, snapped from a moving shuttle bus. These are fairly typical of the island's limestone beds, although not pictured here would be the strata that is more of an orange-brown.
With such an abundant supply of limestone, it is used in many ways. These saw-cut patio tiles around one of the pools contain cross-sections of high-spired gastropods of some considerable size.
More poolside tiles with fossils.
I'm sure there would be some issues if I decided to extract this from the pool side, but it would be neat to be able to prep out the other side in 3D.
There are little spoil piles in out of the way places everywhere. Some of these are discards from being shaped into wall pieces, or stuff to be used as filler elsewhere. I went poking around on the fringes of the property, behind all the resort action. All coral fossils. It's not easy to go scrambling over piles in your flip flops.
This scleractinian coral fossil was my keeper from these piles. I later cleaned up all the dirt pictured on this one, and it looks nice. With luggage weight requirements, I really can't be hauling back anything more than fragments!
Case in point would be this chunk (closeup detail on the right). This stuff is very dense, and without a hammer it becomes nearly impossible to crack out a piece without turning it into dust while bashing against other rocks.
Some in situ pics along the beach where the cliff was close to shore. This stuff is fairly resistant to the pounding of the waves.
Not all the patio material is derived from fossiliferous rock. Pictured here would be "fakes." The left side depict tiles that are clay and based on a mould. The one on the right is simply poured concrete with a sectioned modern shell. Using large leaves as imprints on the wet concrete give it a neat aesthetic.
Ok, so no big fossil haul, but still interesting to bump into fossils while on vacation. When I came back home, there were a number of packages waiting for me, with others waiting for pick up at the post office., They are all trilobites, with a few for me to prepare. Stay tuned...