Today was a gorgeous day, and it is somewhat fitting that the last day of the collecting season be sunny and warm. Yes, this was the last day... I mean it this time! As there are only 11 days left until vacation, a mountain of essays to read and grade, and the fact that winter weather is going to return and stay in earnest, today was it.
The rocks were heavy and hard as always. I didn't come away with as much material as some of them were absolute duds. Like last time, most of the gains were made from a single rock. Let's lead off with the usual suspects:
Left: I think I found this one on a previous trip, but it was in my bag when I was emptying it. Likely a Mystrocephala stummi with mineralized goop on the posterior border of the shell. Right: the ever-present and readily available Crassiproetus crassimarginatus. I am impressed with just how large these ones can get in this material.
There were plenty of Pseudodechenella pygidia (and free cheeks galore), but all of them were on the small side and situated in the middle of larger rocks, so not really worth the effort to reduce and bring home.
When tubercles are showing, that means lichids are in the house. I'll need to clean this one up.
I also found (not pictured) the thorax of a Pseudodechenella that needs to be glued, and a very well defined cranidial fragment (median lobe) with exquisitely detailed tubercles.
This one is pretty tricky to photograph as it seems that my devices try to overly blend the specimen and its matrix. The left is the positive, which still has some parts concealed under matrix. On the right is the negative. Yes, another candidate for Echinolichas eriopis.
A few more attempts to photograph the positive from different lighting angles. What are the chances of finding a new lichid twice in as many days? This one is as large as the one I found Sunday. Whereas the former one has a bit better detail on the pygidial ribs, this one has evident pygidial spines (with tubercles!). There is still an opportunity to reveal more on the right side.
It was nice to end the season on a high note. Although I never quite seemed to find an absolute complete trilobite in this material, these last three months have been filled with surprises. Trilobites in the Amherstburg are very much a faunal minority compared to the thickets of coral and bryozoans, but I made out okay for the effort. The site will now be waiting for me in spring.
Down tools. For real this time!
At this point, I'm just about ready to summarize some key findings, pulled from my field notes, about this imported material. As stated in previous posts, it is reasonable to assume judging by the lithology and presented fauna that this is material from the Amherstburg/Lucas Fms. The nearest and cheapest source of this material for the purposes of a drainage area riprap would likely trace this material to a quarry or quarries in Ingersoll. As it is unsuitable material for cement, this material is generally stripped off.
The fauna is suggestive of a minor reef community. Apart from the thickets of toppled rugose coral (likely due to wave action) and some colonial rugose as well as tabulate (Favosites) communities that have considerable in-fill suggestive of rapid sedimentation burial, the common presence of bryozoans as binders does point to reef development. Bafflers such as crinoids are more scarce in these sediments, possibly suggesting a lack of cohesion and maturity of these minor reef complexes. In some of the materials, thin black layers may suggest a shallowing sequence and possible subaerial exposure in shallow, possibly peritidal conditions. Deeper waters are reflected by the appearance of some packstone pulses with larger grain-size limestones. The upper portion of the material with black stained shale partings or a higher appearance of chert nodules (indicative of siliceous sponges) may contain stromatoporoids, branching bryozoans, and rostroconchs (?Conocardium cuneus). Likely presence of algal mats.
What is known is that this environment would have been situated in the Appalachian basin, southeast of the Findlay arch (by current orientation). It is not unreasonable to expect shared faunal elements with equivalent strata found in New York, such as the Onandaga Fm, and more particularly with the Edgecliff, Nedrow, and possibly Moorehouse Members.
Trilobite fauna are generally represented as a minority fauna in these relatively small coral bioherms. When present, disarticulated moults are suggestive of higher energy conditions, likely swept into gaps and pockets in the biohermal mass. Of note is the complete absence of phacopids, suggesting the environment was not well suited for their spread into this particular biohermal region. Instead, burrowing proetids are relatively abundant, including the illaenimorph Crassiproetus crassimarginatus that appears most commonly in these sediments, followed by Pseudodechenella sp..
Here is a comparative table of trilobites of equivalent geologic age appearing in three locations. A-SITE = the area under study; A-ON-FR = Formosa Reef, Ontario (Michigan basin); O-NY = Onandaga of New York.
As is evident from the table above, only two species of trilobite are shared between the three locations. My location shares three trilobite species from the Formosa Reef, and five with equivalent strata of New York. Two species (in bold) are shared across all three strata.
The seasonal highs for the year have been sticking around after our initial arctic bursts. So, on a sunny Sunday I was back out to my Amherstburg/Lucas Fm spot.
Some rocks I had written off as not as viable have turned out to be much more productive than I thought. Case in point would be another larger piece of armour stone to break down. It seems that, for each trip, there is usually that one rock that gives up the most goodies. So the focus here is on a single rock this trip.
No doubt about this rock being from the Amherstburg Fm, as here is a Mystrocephala stummi (albeit in a rather poor state). Several fragments of the proetids Crassiproetus and Pseudodechenella appear as well, as is usual with this material.
This looks to be another genal spine (possibly belonging to Acanthopyge contusa), but it seems to be curving up and out. The two tubercles on the right appear to be on some kind of axial ring? Huh? I'll need to clean this one up a bit more to figure out where this fits. I initially picked it up thinking it might be a thoracic segment. But the spiny processes seem identical in their orientation to previous genal spine fragments.
A closeup and greyscale image of a fairly mashed lichid cranidium, likely Acanthopyge contusa with the tell-tale scattering of tubercles.
This was the trip-maker. Positive and negative. As is usual in these rocks, the preservation is not ideal. Also, the amount of force needed to split these rocks sometimes results in unavoidable damage in the field where parts of the rock are pulverized forever with no chance of retrieving much more than dust and flakes. The state of the positive (left) had me utter an expletive, but let's focus on what this is and not fixate on its aesthetics. This is not like the many small (~1-1.5 cm wide) Acanthopyge contusa pygidia. This whopper measures 3.5 cm wide.
Notice the middle of the pygidial axis and that it has a kind of prominent "bit" that looks like an oversized tubercle. That is actually the base of a spinal process.
I've grey-scaled and boosted the impression side to better show the pygidial outline. So what is it? We can likely rule out Acanthopyge contusa on account of a few factors (the robust width of the ovoid pygidium, the additional number of pygidial spines --three on each side plus two smaller ones on the postaxial border, the presence of pygidial rib annulations). The pygidial morphology seems very similar to that of Terataspis grandis, with the exception of the short, backward curving spines.
So it's not quite a match for either Acanthopyge or Terataspis -- and yet those are the only two Devonian lichids reported in Ontario. So I tapped the expertise of our Fossil Forum trilobite master to assist in finding the right fit for this oddball. According to him, it may be a match with Echinolichas eriopis, listed as Lichas (Conolichas) eriopis in Hall and Clarke (1888):
(Image from: Hall, J. & Clarke, J.M. 1888
Palaeontology VII. Containing descriptions and figures of the trilobites and other crustacea of the Oriskany, upper Helderberg, Hamilton, Portage, Chemung and Catskill Groups. Geological Survey of New York, Natural History of New York, Palaeontology: Volume 7:1-236.
The spinal process, if complete, would have been quite long. Hall & Clarke report it as being in the "corniferous limestones," which was later revised to the Onandaga Fm. The equivalent strata in southwestern Ontario would be the Amherstburg/Lucas Fms so it fits the geologic age of the material. J.A. Fagerstrom draws from E. eriopis as the type specimen from which he distinguishes E. parallelobatus in the Formosa Reef (Amherstburg Fm), but Rolf Ludvigsen (1987) distinguishes the Formosa Reef lichid as being Acanthopyge contusa. It is not unreasonable to consider E. eriopis as appearing in strata equivalent rocks in Ontario given a shared cratonic basin with New York, but it is not yet reported in the literature, making this perhaps the first of its kind on this side of the border as far as I know, and according to the literature.
So, once again a lichid fragment has me all excited. It means there are still hidden surprises in these rocks after three months of diligent field work. As it looks like tomorrow will be warm and sunny -- perhaps the very last warm and sunny day left in 2019 -- I plan to return to the site and continue my exploration in the hopes of finding more.
Completely unexpected, but the last few days have been about 4-5 degrees above freezing, which has allowed the snow to melt. A partly sunny, snow-free day at 5 Celsius happily coincided with my day off, so I went out back to my Amherstburg/Lucas Fms fill.
I spent most of my time with one very large piece of armour stone that weighed north of a ton. Persistent sledgehammer + chisel + pry bar meant I could reduce it to chips. It was a generous rock, too, with abundant trilobite pieces from top to bottom. In fact, it had numerous representatives of 4 out of the 5 species that appear in this material.
My best find was this Acanthopyge contusa pygidium. Although the rock split was unfortunate, the preservation is actually quite good for this material as I can make out the pustules and pygidial ribs fairly clearly:
I also picked up interesting brachiopods and gastropods (not pictured) that will be going into a gift box. Here are some other trilo fragments from the rock that kept on giving. I am trying to perform relative due diligence in collecting these as I may need to consult with some earth science colleagues to unravel a few mysteries about this material.
Not a bad haul on a cooler day.
So is this finally it for the season? Perhaps, but pending how steady my final essay grading goes, it looks like there will be another potential dig day next week.
And to close out this post, my fossil comrade Malcolm sent me pics of the Eldredgeops iowenesis southerworthi cephalon I found back in the summer. It very much needed stabilization, so I entrusted the prep-master himself. This is stabilized with paraloid as the whole thing was crumbling apart (as is common with Hungry Hollow material).
There's been snow on the ground fairly consistently since the beginning of the month, but I did manage an encore visit to my local spot on November 4, and may have another opportunity for the same this week when the temperature "soars" to about 6 Celsius. When we've seen a few days of arctic blasts that make it feel more like January, you take what you can get!
I've been scratching the fossil itch in a number of ways. I'm reading a few fascinating dissertations and journal articles on isotopic analysis of the Hungry Hollow Member, another on the deposition conditions of the Kettle Point Formation shale, and one on measuring coral ridges as paleoenvironmental indicators of the Widder Formation. And at least one classic by Brett and Landing on the Givetian disconformity in Southwestern Ontario. Some ask why I don't just go and earn an earth sciences degree as (as one postdoc told me) I seem to be far more capable and knowledgeable than most recent BSc grads. Flattering, yes, but I suppose I haven't been presented with that option being a true crime of opportunity. Besides, the one advantage I have in being a well-versed amateur is that I don't have to split my time between the field and the lab (+teaching and grant-chasing); it can be all field fun for me! Besides, if I wanted to pursue a degree in everything I am interested in, I'd need a few lifetimes. The happy medium is to read voraciously and talk shop with the professionals.
This past weekend I went to the annual London Rock/Mineral show. It was great to talk shop with diggers, knowledgeable vendors, and some geo-scholars. It was more a social visit of several hours, as there are not that many fossils at shows like these -- mostly minerals and jewellery. Most of the fossils on offer were the usual common stuff, like polished Madagascar ammonites, Utah trilobites (i.e., endless Elrathia kingii), etc. But I did buy something from a French vendor who was a geology teacher in Morocco and knows all the big paleo names that have done research there.
Fairly common Moroccan bugs that I got as a package deal. Not the best prep, either, but passable (and not butchered). The vendor was up front about some areas that have light restoration, although I could pretty much tell upon having the specimens in hand. To my collecting shame, I didn't yet have a complete Reedops cephalotes, which is fairly common. My first one is missing half of its back end, so it was nice to have one complete and prone. It is about 80 mm. The one at the top of the picture is the classic Paralejurus rehamnanus and measures about 70 mm.
The other fossil-y thing I did this weekend was get back to some drawing that had been put on hold due to teaching/grading duties (and so is again back on hold as I navigate what remains of the semester!).
Calling the season's time of death today on November 1. And so it is down field tools for 2019, and taking up the prep tools for winter (may it be short and merciful). Unless there is a miraculous change in weather to permit an encore, this is it. The next two weeks look like pre-winter is setting in, and the last two weeks of November are a bit of a write-off as the end of semester grading will suck up all my available time.
In retrospect, it is tough to pin a qualifier on this collecting season; neither was it the best nor the worst. Like life itself, there were incredible moments/finds that punctuated a series of disappointments. Not that many new trilobite species were added to the collection this year, but the few added were nothing short of exciting. I ranged from the Ordovician to the Devonian.
I’ll kick things off with this year’s disappointments first to get that out of the way.
1. My local honey hole that had pretty much ran dry the previous year had not produced anything new from weathering; in fact, it has been steadily overgrown since I first collected there in 2013. A few desultory visits during the spring mean splitting shards from my own previous trips. Tapped out.
2. Our upper Widder spot was quickly made off limits by mid-April. Fortunately, I did find a really nice and large placoderm dorsal plate before the window of opportunity slammed shut. As that spot was the regular go-to for our out-of-town crew (and fossil comrades who visit once a year), that put a major dent in options this year. This would be the first year since I started that there would not be a season to develop the site and extract Widder goodies. Also, extensive work at that location for so many years has pretty much made it unsafe and not so viable for excavation. We had to fall back on prospecting new areas, and defaulting to the Hungry Hollow Member, which is not exactly the easiest stuff to work with -- it's muddy, chunky, coral-infested, fragile or shattery.
3. The annual trip to NY at the end of April was brutally cold with sleet and snow. I also came up empty-handed from my trip to Deep Springs Road (apart from field comrade gifts, of course!). So no full Dipleura found.
4. A second trip in August to Penn Dixie did net a few buckets of material, but the exposed area for excavation was brutally hard, unweathered, and likely a point where the trilobites were pinching out laterally. It meant twice the work for half the haul.
5. A road cut in the Cobourg Fm that I prospected in July turned out to be a bust when exploring it in more detail in late September.
6. A second trip to Bowmanville, which is usually the capstone of the collecting year in autumn, was preempted by car trouble.
6. Plans to visit some very coveted private spots did not materialize for one reason or another.
But it wasn’t all a bust, strikeouts, and skunked trips. I can count a few victories this season:
1. Finding one of the largest placoderm dorsal plates found in the Widder.
2. Plenty of improvement at the prep bench, in addition to new tools (PT Aro and ME-9100), new higher capacity compressor, and a top shelf camera.
3. Finding a perfect Flexicalymene croneisi prone specimen during the June Bowmanville trip. Finding them prone is rare as opposed to enrolled.
4. Prospecting that new spot near Nottawasaga Bay — even if it turned out to be an unproductive dud later on in the season.
5. Any and all time spent with field comrades from near and far: Malcolm, Greg, Kevin, Roger, Don, Paleo Joe, Tim, Jeffrey, Jay, James, and everyone else I broke rocks with this year.
6. Finding a nice, large cephalon of Eldredgeops southworthi in the Hungry Hollow coral-tangled muck-rock. We sourced the layers from a new, untouched spot (now pretty much tapped out).
7. Finding a new local honey hole on August 22 that was a real game changer that truly turned the season around. It is there that I pulled out my first Terataspis grandis fragments, and two nearly complete Pseudodechenella sp., in addition to a healthy number of Acanthopyge contusa, and a two examples of Mystrocephala stummi.
8. A fascinating trip to the type locality of the Formosa Reef member of the Amherstburg Formation, focusing on the windward flank netted plenty of goodies.
9. Not collecting-related, but I took to drawing trilobites seriously this year with substantial improvement — enough to have a few of them featured in The Trilobite Papers.
10. Compiling a master list of Ontario trilobites has become its own archivist’s passion.
So, on balance, 2019 had its ups and downs with the “ups” cancelling out a lot of the “downs.” With more site closures and stuff tapping out, this was a year to forge ahead and explore new possibilities as opposed to being resigned in not letting the hammers ring. I didn’t buy many trilobites this year, which can account for the decline in species-adds this year. That being said, costs were still a bit high given new equipment and a few sunk costs on accommodations.
Trip Totals (days):
Local honey hole (old spot): 4
Local honey hole (new spot): 25+
Penn Dixie: 5
(~50 days) (last year ~34)
I was able to get out there more this year than last year despite a narrowing of site options. Now on to what I consider to be this season’s top finds:
New species to the trilobite collection that were a result of my fieldwork include Pseudodechenella sp. (from the upper edge of the lower Devonian; not yet clear on which species, but they are distinct from other examples of the genus found later in the Hungry Hollow Member), Terataspis grandis, Acanthopyge contusa, Mystrocephala stummi. So that makes two new proetids and two lichids. So, like 2018, my self-collected tally for new species was 4. There may be more than that, but I would need to spend time with Lieberman’s text on proetids of Eastern North America to determine if I have any species variants of the many Crassiproetus pygidia I’ve collected from my Bois Blanc / Amherstburg material.
This is a good time as any to feature all the Acanthopyge contusa heads and tails from my new local spot:
As I also found genal spines (but no determinate thoracic segments), I sketched a quick reconstruction that perhaps I'll try to formalize as a better illustration in winter:
In my dogged pursuit of long dead things, I shared my collecting spots with living things, too:
And, O! the messes we will make. Some snaps of sites and fossil comrades breaking rock together.
Now that fieldwork is at an end for 2019, it is time to start planning for 2020. Last year I didn’t plan as well as I could, which meant kind of starting off on the back foot. That, and a delayed spring and taking a few sites for granted, meant not optimizing on the time I usually have off once the academic year is over. So now begins a sitting down with the maps and to carve out the areas throughout Ontario that could use some pioneering work in exploration and prospecting, if not also visiting now forgotten spots.
I also received a lot of of great gifts from other collectors this year, and performed a lot of prep, but this end of year report is already fairly picture-heavy as it is.
Although I don’t have a massive amount of material to prep for winter, I still have some work I can do. Perhaps it is just as well since in terms of time: I’ll be teaching a heavier load in winter in addition to taking a sunny holiday in February. There will be more blog posts in the off-season as I tend to get caught up in some fossil thing or another.
On a warm Sunday, I made it up north to the Formosa reef road cut. It was likely my last major trip of the season, and it certainly did not disappoint. I had read and re-read the research papers on this site, which is the type locality for this massive biohermal feature situated in the Amherstburg Formation. The two main sources would be these:
Fagerstrom J.A. (1961) The Fauna of the Middle Devonian Formosa Reef Limestone of Southwestern Ontario. Journal of Paleontology 35.1: 1-48.
Ludvigsen, R. (1987) Reef trilobites from the Formosa Limestone (Lower Devonian) of southern Ontario. Can. J. Earth Sci 24
The road cut itself is quite sizeable, and represents a massive knoll. My focus was on the windward side of the reef where skeletal debris would have been swept in by currents. The wackestones and stromatoporoidal boundstones contain a staggering amount of faunal diversity. There were certainly corals, both tabulate and rugose, but just about everything else including gastropods, brachiopods, bivalves, crinoids, and a profusion of different kinds of nautiloid. Of course, there are trilobites as well, but none have been reported complete.
The cut runs along both sides of the road, with additional access from behind the reef as well.
And it is fairly tall, too. There really is an abundance of material, much of it more fossil than matrix. What we collected in 2.5 hours is hardly representative of what this material has to offer.
This was the main focus of the visit: the windward side of the reef. Every single rock was full of fossils -- and not just coral. The weathering and oxidation made for some interesting steinkerns.
Although the material looks quite dense as it weathers a dark grey (inside is a creamy off-white with orange oxidation), it breaks apart easily. Unlike a shale that will split in sheets, this material breaks apart in angular chunks, a little like the material at Hungry Hollow (but much clearer to see what's inside). Pictured above are some usual surface features including a nautiloid cast and a chunk of tabulate coral. The material was quite easy to work with.
It took just a matter of minutes to start piling up stuff to bring home. Every rock and every split had something new and interesting. Of course, I wasn't too picky about what I was collecting as this was my first visit. It is a little like someone's first visit to Arkona when the tendency is to fill buckets with horn coral!
Nautiloids were abundant.
Weathering made for some very neat looking cross-sections, as pictured here with the exposed siphuncle.
This would be my first cyrticonic nautiloid. Quite neat!
I found a number of these small rostroconchs, too. Of course, I'm pretty full up on rostroconchs from my local imported fill site.
Plenty of gastropod steinkerns, some flat and others high-spired. Some also contained large crystals inside. There were also plenty of brachiopods of varying types, but I didn't manage to collect them this round.
Deb found this large, double-valved bivalve that popped free of the matrix. I had found a smaller more beat up one, so this example was the clear winner to be taken home.
Corals, corals, everywhere. Some had very nice crystallized cross-sections among the rugose variety, but we left those in the field. Despite this being a reef, the corals were less "in the way" compared to the Hungry Hollow Member at Arkona; many more types of fossils were given equal billing. Also not pictured were the crinoidal hash.
So what about the mud bugs? Ludvigsen reported that trilobites were rare in this material, and that is not something I could confirm from experience; just about every rock had some kind of trilobite fragment, be it a pygidium, cranidium, or librigena. By far the most abundant species would be Crassiproetus crassimarginatus (subspecies brevispinosus). Pictured above is just one (exfoliated) example of about ten or more I brought home, leaving about as many or more in the field! Ludvigsen's text reports 222 fragments found over a matter of a few years; I could probably acquire that many in a full day there. Of course, no complete example has ever been reported, and it is unlikely due to the nature of the depositional environment. One has to be content with partials.
If Crassiproetus is the most abundant trilobite represented there, the second most would be Mannopyge halli. Pictured here is a rather beat up version, and it was odd I only found the one -- but then I may have missed a few in the haste to make the most of our short time at the site. You can see the pygidial nodes like a necklace along the right edge.
In third place for relative abundance would be Mystrocephala stummi. I was pleased to find this fairly nice example which looks a bit more well articulated and robust than the more flattened examples I've found at my local spot (yes, I found a second fragment a day before this trip!). No traces of the other two most rare trilobites in this material (Acanthopyge contusa, and Harpidella sp. of which the literature reports a single cranidia).
Overall, this was an incredible trip filled with new surprises. Although I had to miss out on Bowmanville this autumn, this certainly was a significant event of the season. I do plan on returning there again, either later this year or more likely in the spring. I hardly did this site justice as there is still so much to explore.
The long October weekend is here, and despite it raining this morning, I was able to get out yesterday and have plans to make a few visits to my Bois Blanc Formation rubble between bouts of turkey and getting caught up with essay grading.
The number of rocks that are highly fossiliferous is dwindling, but I'll have enough to see out the rest of this year. This small haul of trilobite partials would be considered a fairly good outing: three fragments of Acanthopyge contusa and two fairly preserved pygidia of Crassiproetus crassimarginata. That brings my total Acanthopyge fragment count to about 9, and 13 lichids overall. If I could only find a complete example, I could stop collecting the fragments.
As the material is very rostroconch-dominant, I only pick up the odd one on occasion if they look nice.
I hope to get out a few more times in the next while and update this post if more neat finds are made. So, to be continued...
So another four hours out back, and I didn't do too poorly. It took me a bit longer of trial and error to find the right productive rock, and it was this one rock -- and only this rock -- that produced the days finds.
I suspect this to be another lichid genal spine (possibly Acanthopyge contusa). Left: negative and positive. Right: closeup.
Just missing its cheeks, an otherwise complete Pseudodechenella sp. None too shabby! This would be the day's best. Perhaps I'll have another go tomorrow.
Well, it was a challenge to find more productive rocks to split. Four hours, and not much to show for it. In fact, it was the first visit in some while where I didn't even find a trace of a lichid. But sometimes a small find can be just as rewarding.
This looks very much like a Mystrocephala stummi to me (compare with the image from Ludvigsen on the right). If so, that would make a new species find for me. Although the pygidium axial width is not 1/3 or more of the entire pygidial width, I can make out the little nodules along the heavily incised pygidial ribs. Of course, the fact that it is only reported in the Formosa reef (Amherstburg Fm) possibly problematizes the assigning of this rock to the Bois Blanc, but so did the appearance of Acanthopyge contusa. There's trilobites from both formations here, sometimes on the same bedding plane. Perhaps another visit tomorrow? For now, round 1 of turkey.
Five hours and I've pretty much managed to tap out a section of much of the viable rock. It wasn't until the last half hour that I was able to find anything at all, with much of the time spent splitting duds, blanks, bits, and other false leads. If the fourth of four sections has any viable rocks left, they are massive armour stone boulders that even I can't either move or do more than splinter/fracture the edges. So on I moved to section two.
As with a lot of the lichids in this material, the preservation is generally poor, but this Acanthopyge contusa positive and negative is still fairly articulated with the course tubercles and delineated goblet-like pygidium axis. That brings me to 15 lichid fragments, with eleven of those from this species. I probably have more examples of this species than any museum.
Once more into the breach before I give the site a rest for a bit. My focus tomorrow will be a return to section two. There's still some source rock to go through from where I obtained this pygidium. If time and energy permit, I might poke around section one (fairly tapped out) and section three (mostly blank or lenticular coral limestone + domes). I've put in 16 hours in 4 days.
And another five hours in the proverbial hole, and that will be all for now as I need to get back to much-neglected work. But on to the finds that close out these five days of persistence.
Yes, it's yet another Acanthopyge contusa. Although the photo doesn't do it much justice, this is a very nicely preserved cranidium despite missing a lobe on the right. The tubercles are nice and clearly defined.
The trip-maker? What appears to be a cranidium that compares favourably to Terataspis grandis. Image on the right is from Ludvigsen's text. But, sadly, it is just another Acanthopyge.
Here is the same specimen in sunlight, and the negative below.
So, the final tally:
5 days (21 hours)
12 Trilobites (7 lichids, 4 proetids) = 7 Acanthopyge contusa, 2 Pseudodechenella sp. (one almost complete), 2 Crassiproetus crassimarginatus, 1 Mystrocephala stummi
Not bad at all. Spending all this time out there has forced me to revise assumptions about this material, and it may be a blend of Bois Blanc, Amherstburg, and Lucas Fms. Not sure when I'll be going back, but my hammering arm needs a break!
When it rains, it pours.
With what were to be the last big two trips of the season -- one to my prospected Cobourg Fm roadcut near Nottawasaga Bay, and the other to Bowmanville -- were bust.
The trip up near Collingwood did not yield any complete trilobites. Worse, the stuff was weathering into blank, undulating nodules with the occasional bits. Small, junky fragments of about five typical Cobourg Fm trilobites were all I came away with, and the usual giveaway gastropod steinkern and miscellanea. I spent a good deal of time (including in a misting rain on a cool morning) splitting to no avail, and surface collecting the weathered rubble to slightly better luck. Photos of my underwhelming finds:
So, Isotelus, Flexicalymene, Ceraurus, Pseudogygites... in fragmentary form + gastro and sundry bits.
The "prize" were all these Thaleops cephalons. So, fairly skunked for an eight hour round trip drive. I won't be bothering this roadcut anymore.
As for Bowmanville, funny story. Forty clicks out from London as we are making our way, our car decides to give up the ghost on the 401. That means getting a tow back into town, it means not being able to get refunded for a hotel room some three hours away, and it definitely means no coveted Bowmanville trip for me. As trips to the quarry are limited to the two times a year they let collectors in, and with a new rule about putting a hard cap on the number of collectors, my luck in not being bumped to the waiting list for next spring meant little if our wheels would not get us there.
So, what was going to be the final big trip of the season went up like a puff of smoke. That bummed me out a bit. But the season is not quite done as I continue wrestling the stone at my personal backyard spot.
It's a lot of fighting to get the rocks out and broken down, with some just too large to do much other than shatter. But here's another pygidium of Acanthopyge contusa.
Genal spines belonging to another lichid, but unsure if it belongs to Acanthopyge or Terataspis. None of my literature describes the genal spines of Acanthopyge contusa, so it remains uncertain.
A giant and fully inflated Crassiproetus pygidum.
Two poorly preserved lichid pygidia, and an uncertain fragment.
Another Acanthopyge contusa cephalon (two angles).
The mystery deepens, or am I closing in on the formation these rocks are coming from? I still need to retrieve the positive, but my trilobite comrade Scott says it seems to compare to Trypaulites erinus. Initially, I had passed it off as a Pseudodechenella until I got home and looked at more closely: too many pygidial ribs and an axis much more tightly tapered. A dalmanitid! This one sits on the exact same bedding plane as the Acanthopyge pictured above, with only about 3 cm of daylight between them. So... what are these rocks? According to the reported material, the Bois Blanc Fm has the following trilobites:
The ones in bold are those that I have found in this imported fill. But the trilobite out of place here is the Acanthopyge contusa that is only reported in the overlying Amherstburg Fm. The evidence seems more to suggest that a) I am dealing with Bois Blanc material for sure, and b) Acanthopyge specimens in the mix may mean it had a longer geological range, first appearing a bit sooner. That would not be an entirely absurd hypothesis.
The rocks at my spot are starting to thin out in terms of giving up nice finds, taking much more effort for less reward. As the days grow shorter and colder, the fossil days of the season are in their twilight. That being said, it is not officially "down tools" yet; there are still a number of weeks left where I can squeeze out the odd day or two a week between teaching duties.
In the hopper is some planning to visit the type locality of the Formosa Reef (Amherstburg Fm). Full trilobites in those reefal environments are as unlikely as my current backyard spot, but I'm hoping to find a fragmentary example of at least one species of trilobite I do not have as this year has been a bit light on collecting species I don't already own. I'm also expecting a scribe I picked up for cheap that will bridge the gap between my ME9100 and the Aro, and I have another Asaphus lepidurus coming to be prepared. Looking over my materials this year, I'm not sure I'll have enough to last me through the winter, so I may spend more time planning out the 2020 season.
But it's still the 2019 season. I will continue breaking rocks until the snow comes.
On Wednesday, Friday, and Saturday, I managed to get to my nearby site for more challenging rock splitting. On Wednesday, I found a second cephalon example of the lichid Acanthopyge contusa (see the update to my post here). Friday was a bust apart from the usual fauna, taking home only a few common proetid partials and a few unknowns that turned out to be nothing interesting when I got them under the microscope. Today (Saturday) seemed to make up for Friday's failure.
These are the tools that come with me in my backpack. I added the small pry bar today. Some of these rocks are veritable boulders that run deep, and since they are already extremely tough material to break, nothing comes easy. Even when the material doesn't shatter uselessly along a diagonal across the bedding planes, smaller chunks like to split vertically rather than horizontally as the beds can be so thinly packed and dense. Finding the right rock usually comes down to certain external features, but even then those can be blank duds or simply sparsely fossiliferous coral zones. Before committing to any larger rock, I test the edges to see inside first. The tool most often used in my arsenal at this location is the hand sledge.
When I say typical fauna, I mean the litany of fenestellate bryozoans, brachs, and trilobite partials. When I "test" the rock, these are the kinds of layers that usually show the most promise.
I am tentatively going to label this Acanthopyge contusa, although I am not fully certain it might not be another Terataspis as they have similar pygidial morphology. In some aspects, it seems to resemble both, but the preservation is not the greatest on this specimen. Going with the more conservative estimate, that would make Acanthopyge example number three.
Every split requires a careful scan so as not to miss something spectacular. I almost left it thinking it was a compromised brachiopod, but the notch on the bottom made me think it might be a hypostome. And, surely enough, it is a hypostome belonging to Terataspis grandis. Pictured on the right is the illustration by R.P. Whitfield (1897). That makes three examples of this rare lichid, although compared to those found by others and housed in museums, mine are all quite small. This example is barely 1 cm, while the one at the ROM is 7.5 cm. Still, a mini-monster is still a monster!
Sunday update: Spent another five hours out back and I would say these two partial examples of Acanthopyge contusa were the star finds:
Wednesday update: Another three hours as I steadily run out of viable rock. This is one specimen split between both halves of the rock. It is my fourth fragment of a Terataspis, specifically the genal spine. My tally now is two pygidia, a hypostome, and a genal. The likelihood of finding a complete one is along the same odds of winning the lottery, but how many trilobite collectors can lay claim to having even just a single fragment?
I'll be off this weekend to my secret Ordovician location up north, so I hope to post my finds when I return.
I've made a number of return visits to my local spot, but sadly have nothing remarkable to show for it. There is only one type of rock that is both fossiliferous and containing trilobites, and that rock type is a very thin minority at this location. I may have encountered nearly every example of it by now, including boulder-sized ones that make granite seem like butter when it comes to getting into without just creating powder and shards.
So my attention turns to other things, such as creating a kind of an updated master list of trilobites in Ontario. By drawing on the key sources, such as Ludvigsen and Isotalo (among others), this forms a basis for creating such a list. Formation names and taxonomic classification changes have been reflected in creating this list. I've added reasonable correlations based on similar strata in the US, both the Michigan and Appalachian basin. Those correlations appear in a separate column, and are not included in the Ontario species count until they can be found and confirmed in Ontario rocks.
I've also excluded Hudson Bay and James Bay trilobites on account of a lack of more sustained formal description. The list therefore only includes paleozoic rocks south of the Canadian Shield, or simply "southern Ontario."
I am told that there is some anticipated and ongoing taxonomic revision that may result in having to update this list, but revisions are to be expected anyway.
It should also be noted that more than half of these specimens could be classed as quite rare, or known only as fragments. Finding accessible outcrops remains the perennial problem for trilobite collectors and researchers in Ontario, and so even attempting to perform a reliable volumetric analysis of certain formations is imperiled by a lack of substantive sample size.
But this revised list is a good start which tells us something about the trilobite record here in Ontario. I expect to be updating this master list as new resources come available.