Phacopids had a late start in the Ordovician, and were wiped out by the end of the Devonian. They were extremely diversified, and we can credit them for the development of schizochroal eyes as opposed to holochroal lenses. Someone like Richard Fortey is all over the eye development of trilobites like a dirty shirt! Pictured here is the iconic Eldredgeops rana (previously Phacops rana for all the older collectors out there!). Note those distinctive eyes. We really start bumping into this new bumper crop in the Ordovician with all the Flexicalymene, Calyptaulax, and the incredible diversity of the cheirurids. By the Devonian, their diversity thinned out. There were some massive calymenids in the early Devonian, but all the cheirurids were gone after the Silurian. Eventually, it was these phacopidae and Geesopines that survived. As my dear collecting comrade says, Eldredgeops is like the cockroach of the Devonian. Their emergence in the Eifelian and Givetian was madly prolific. Proof? Now that is one gregarious assemblage!
Given their diversity, it is no wonder that almost half of my collection (roughly 60 of 150 species) is phacopids. Unlike asaphids and lichids, they never attained massive proportions. They were, however, very resilient and there is likely no continent on earth that doesn't have a few phacopids in their fossil record! Exceptions to big sizes might be Drotops from Morocco or oversized Ceraurus. The biggest authentic Drotops I've seen is about 16 cm in length -- not tiny, but not exactly a mature Uralichas either. They're bumpy, spiny, and ugly... And they are my absolute favourite of the trilobite orders. They are also fairly rare to find, and even digging in the postal formation means paying top dollar for what amounts to an expensive taste in trilobites! Many lichids have a great deal of very developed microsculpture, with spines and tubercles likely an evolutionary trait designed to deter predators. They were particularly successful, ranging from the mid-Cambrian to the upper edge of the Devonian. Perhaps the very best researcher on lichids would be Thomas Holloway. His work on the phylogeny of this Order is worth the read. Lichids have many classic and coveted members, including Arctinurus boltoni, the "emperor of the Silurian seas." Some of them were bona fide giants, such as Terataspis grandis, which is the third largest trilobite ever recorded. Pictured here is just one of many fragments of Terry that I have found. Although localities in Morocco and Russia have some very impressive lichids, Canada is near the top of the list as well. In our Ordovician deposits, we can count Hemiarges and Amphilichas among our crew. In the Devonian, we can add Echinolichas, Acanthopyge, Ceratolichas, and of course the great Terataspis. If we only had more outcrops of the recessive Rochester shale of the Silurian, Arctinurus would be popping up more often! And there is no doubt that we still have some undiscovered lichids in our arctic, too. I've been fortunate to find most of Canada's lichids, albeit as fragments (and I probably have more Terataspis fragments than any museum on the planet!). The early days of lichids in the Cambrian were fairly modest in terms of how dramatic they became. If we consider Damesella with its fine granulations, it more resembles a cheirurid than a lichid. An illustration of one I did last year: So let's compare to the great Terataspis. This reconstruction line drawing will need some revision, and that will happen once I have all my pieces prepared. Included here is an Arctinurus that I think is at the ROM. Despite the very dramatic surface features, their hypostomes are surprisingly dull. I have collected nearly all the Devonian lichid hypostomes in Ontario, and they are nowhere near as defined and eye-popping as an asaphid's. Pictured here is a Terataspis hypostome I found in some glacial till. Pretty unremarkable!
Corynexochids are the second longest surviving Order of trilobites, ranging from the Cambrian to the end of the Devonian. We know this bugs mostly from their more common representatives like Illaenus or Bumastoides. One feature many of them have in common is the effaced nature of their cephalons and pygidia. These trilobites were uniquely adapted to very muddy environments, likely preferring to burrow in sediment. I've taken more of an interest in this Order in the last few years, for despite the simplicity of their body plan, they are fascinating creatures. In the Rochester shale, they can be more commonly found among bryozoan thickets, suggesting some kind of potential symbiosis or food source. Not all of them were devoid of ornamentation. If we consider the genera of Zacanthoides or Changaspis from China, we see that they were not all effaced. And then we have the Moroccan genera of Paralejurus and the scutellids like Scabriscutellum and Thysanopeltis with a distinctive rim of pygidial spikes. The scutellids and styginids are fascinating in terms of phylogeny. In entomology, we know the term "scutellum" referring to a posterior feature resembling a shield, and we see that quite distinctly in the deeply incised furrows of the pygidium of Scabriscutellum (Morocco) or Scutellum lunatus (Minnesota, USA). Another interesting feature was that they could attain to impressive sizes. If we consider Ectillaenus giganteus from Portugal or Ectillaenus benignensis from Morocco, they could reach fairly robust sizes. Canada is not as blessed with corynexochids. We can count among them Bumastoides, Bumastus, and Ekwanoscutellum, I consider myself lucky to have 15 distinct species from this interesting Order, including the handlebar mustache of trilobites, Illaenus tauricornis. Having prepared a few from Russia and partials here in North America, I have come to deepen my appreciation of this true mud bugs.
The asaphids are an incredibly diverse and successful Order of trilobites, and one of my absolute favourites. Not all asaphids have such stout, simple body plans. If we consider the large panoramic-eyed pelagic types or Hypodicranotus with the longest hypostome in relation to the body, we see that they are anything but "simple." In Canada, perhaps the most common trilobite to find in Ordovician rocks is the classic Isotelus. Flourishing from the Cambrian to the end of the Ordovician, they certainly dominated the seas on account of the impressive sizes they could attain. In fact, the biggest complete trilobite ever found is Isotelus rex, measuring 72 cm in length, and found by Dave Rudkin and his team in Churchill, Manitoba in 1999. The asaphids have had a lot of twists and turns in their development. If we consider the Russian asaphids, we can plot out the gradual increase in eye stalk length beginning with Asaphus cornutus, and then a bit more with A. punctatus, A intermedius, and finally the classic longest eye stalks belonging to A. kowalewskii. Eye stalk length is likely indicative of an adaptive trait in being able to burrow into sea floor sediment with just the eyes poking out. Other evolutionary traits include the elongation of the cephalon and pygidium, as can be seen in Megistaspidella and Ectenaspis. It is uncertain what purpose this may have served, but it is possible it assisted in more effective burrowing in sediment, if not also possibly a hydrodynamic benefit for swimming. Of course, most asaphids (not all) were nekto-benthic. They could certainly attain gigantic sizes; in Canada, giant Isotelus could reach a length of over 30 cm. Although size can be a great adaptive trait, it also can lead to some problems. We can reasonably assume the most fierce predator of the Ordovician seas would be nautiloids, and so being a bit bulkier may have proven an advantage. That being said, maintaining that size means a heavier dependence on available nutrition. Since trilobites moulted up to 30 times in their lives, energy requirements were likely quite high. Another unique feature to many asaphids is the hypostome. These quite often take on the appearance of a "fork." The purpose of the hypostome is still debated. Was it for rasping and feeding? We can credit the excellent research of Thomas Hegna for exploring this in more detail. For reference, see Hegna, T.A. 2010: The function of forks: Isotelus‐type hypostomes and trilobite feeding. Lethaia, Vol. 43, pp. 411–419. But perhaps the most interesting hypostome among the asaphids belongs to Hypodicranotus where the very extended fork runs almost the entire length of the body.
There is no doubt that I am a big fan of asaphids! They make up about a fifth of my collection in terms of distinct species. They were fairly resilient, too. If we consider the deep anoxic environment of the upper Ordovician that laid down the black shales of the Whitby Formation, it was an asaphid and one ptychopariid genus that was able to withstand that environment. In fact, the very first trilobite to be described was an asaphid, and the first trilobite in Canada to be described was... an asaphid! Although they were beneficiaries of the Ordovician biodiversity event (ODE), theirs was a candle that burnt twice as bright and was snuffed by the widespread extinction events that closed out the Ordovician. The torch would be passed to the other remaining Orders of trilobites. While we wait out the winter, I may as well talk trilobites. Of the now 14 established orders, the Agnostida are an odd outlier in the trilobite clade. These diminutive trilobites emerged during the Cambrian "explosion" and vanished at the tail end of the Ordovician. There has even been dispute as to whether to include them as trilobites at all! Perhaps the most well known of the Order would be the very common Itagnostus interstrictus from the Wheeler shale in Utah. Agnostids were blind trilobites that may have been semi-pelagic or even benthic crawlers -- it is still a matter of debate. It can be challenging to determine what side is "up"! Not all agnostids have effaced features, as there are some from the Cambrian deposits in Russia that are quite textured.
I can't say that I have too many specimens of this unique Order (just a few) as I don't collect much material from the Cambrian. They are not particularly showy given their size and simple morphology, and they are closely related to the eodiscids, which have since been erected to their own standalone Order. Shergold (1991) argues that they are distinctly different. In many ways, they resemble other trilobitomorphs, but they have just enough similar morphological traits to include them under the trilobite banner. Those interested in learning more about the agnostida are encouraged to delve into the Treatise O: Arthropoda. See as well: Cotton, T.J. & R.A. Fortey. 2005. Comparative morphology and relationships of the Agnostida. In: Koenemann, S. & Jenner, R. (eds.). Crustacean Issues 16, Crustacea and Arthropod Relationships (CRC Press: Boca Raton). 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. There may be snow on the ground, but my mind closely orbits the shining star of the 2021 fossil season to be. At this point, I have plotted out several of this year's routes that will pass through many, many locations, with a goal of trying to top 2020's spectacular season. As I look longingly at the calendar, or check the long-range forecast for any hint of a possible early spring, fossil-related activities continue (albeit of the indoor variety). First up would be a long delayed and necessary reorganization of the entire collection, in addition to a deep clean / reorg of the prep area. And this would not have happened without my wife, Deb. I am sure I would just live in a cluttered squalor without her, not being able to find key fossils without much difficulty. It was her intervention that got me organized, and that she and her son put up an enclosure around my prep area to cut down on dust. For those who have collected, and stayed, with me at chez nous, one could not have a much more understanding and perfect spouse. When we are away for a week, coming back all furry and smelly, subsisting on a road cuisine diet, Deb gives us a perfect meal and beer. I am the luckiest ever! Anyhow, let's get to Deb's inspired reorg... This was an eight hour task, necessitating going through each of the fossil flats and various containers where I dumped six years of collecting. Much of it was mixed up, so I had to sort by location and formation. I transferred everything into beer flats and labeled them. A few hundred pounds of junk were pitched away. All of that had to go somewhere, as opposed to being in near-toppling stacks in the living room and all over the basement. So, this wire shelf unit that can take up to 2,000 lbs. About 33 flats all organized. Phase two was a thorough cleanup of the prep area. This also involved cleaning out 3-4 inches of dust from the blast box. I've even MacGuyvered an old tool belt attachment to hold my scribes (tips rest on an old work glove). There are four flats of fossils that are my prep queue. The bonus of going through all of this, apart from finally being more organized, is I kept bumping into fossils I had forgotten about, some of which I had tried to prep with primitive tools and abandoned. Phase three was the addition of a thick plastic enclosure to keep the dust at bay, secured with tuck tape and with one slit to allow me entry. It's very ET/quarantine of me. Not pretty, but functional. Taking the prep area out for an initial try-out, while doing some prep on Neuville Fm material, I happened to uncover this neat little number. It is a plate from a rhombiferan, likely Cheirocystites anatiformis. I'm doubtful there is more, but I can poke around and find out later. This was on a small slab with a partially enrolled Ceraurus pleurexanthemus. This was a welcome surprise. I had found this Bellacartwrightia at Penn Dixie in October 2018. The photo on the left was its field state. I tried prepping it (with hand tools, no less -- argh!) and it seemed to me to be headless, so I dumped it in waste box of misfit fossils. My organizational frenzy rediscovered it, and I decided to do a bit more investigation under the scope. Lo and behold, it is near complete. The cephalon is tucked over on the other side. These tend to more commonly appear like flat sandwiches. But this will be a neat project of a rare trilobite (the occurrence is something like 1 of these for every 10,000 Eldredgeops rana found). I will need to abrade the left side and then work on the cephalon on the reverse side. It will take a bit of stabilization first. Sadly, it is missing some of its right pleural tips, but those may be easy to restore.
A notice in the mail says I have a package waiting for me at the post office, and it is likely my six Russian bugs to prepare. I picked the right time to organize and clean! It's been a while since I updated the blog. Welcome, 2021! I have been working steadily on planning the following year in between my day job responsibilities, coordinating planning with my field comrades, and priming myself for a hopefully early spring. There will no doubt be some incredible adventures this year, most of which I will sadly not be able to disclose publicly for fear of mercenaries looking to steal a march on all our hard work! My trilobite searches are rigorous. To quote the great Ludvigsen from 1979(!): Exceptionally preserved specimens of trilobites are becoming increasingly difficult to find in Ontario. Yup. And that was before no further quarry access, housing development, park designations, and sites being tapped out in the last 40+ years. Sometimes I think those of us collecting now are the hardest workers of all. But I have a feeling this year will be a banner one. But I'm almost ready. So, for this post, some updates. Hoo-boy! This 11 cm beastie is the classic Megistaspidella triangularis purchased from my very favourite Russian connection who also digs and prepares his finds. This was a bucket-lister for me. Note the triangular prow that likely was in service for digging into sediment. Our closest equivalent in the Ordovician Iapetus ocean here in Ontario would be Ectenaspis homalonotoides, originally dubbed Isoteloides. Asaphids finally got some purity in the last year when the trinucleidae family was turfed and raised to their own Order. It was folly to include them in the first place! And a drawing, which took me a ridiculously long time to finish. A Basseiharges mellishae from Jorf, Morocco. These lichids appear in partially metamorphosed rock, which accounts for their diagenetically reworked plasticity in appearance as opposed to showing crisp pustules, which would be more typical of most lichids.
I do have two others in the drawing queue once I get the momentum and time to do them. One is a fully pustulose Metopolichas, and the other the classic Arctinurus (also pustulose). Pustules take forever to draw meticulously. It takes longer to draw than to prep them. So, much blood and treasure shall be spent in the adventures this year, so I'm hopeful of some kind of return. I have a number of other pieces coming that will be prep jobs, so brace for updates on that. In terms of me giving clues to where I'm going -- not a chance in such a public space! But they will be remarkable. |
Kane Faucher
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