Spent four hours yesterday at my Bois Blanc location specifically targeting Terataspis. Overall, it was a great day for it -- sunny and warm. In fact, it was the first time this season that I've had to strip down in the field as I was actually sweating, and now bringing water to digs is essential. That weighs one down, but dehydration can impair a good dig.
Let's kick it off with Deb's lovely find. A lot of it is still buried in matrix. The telltale small, rough tubercles are present, which says Terataspis.
A field shot. Likely a portion of the pygidium, thoroughly eroded. The character of these rocks make it a challenge to find nice pieces if one were to rely solely on just surface collecting. The real trick is to investigate breaks in the rock for long lines where their parts are still buried, or to find a small piece showing on the surface that continues under the matrix.
Another in the field eroded piece. It appears to be a a disarticulated series of thoracic segments, but there is some work in the lab to determine if that is the case.
An isolated pygidial spine with the characteristic barbs. There could be more, but doubtful much more. Some time in the lab cleaning it up will say.
What looks like a pitiful, junky rock may actually be covering over a nice piece here. The more obvious component with the tubercles may point to this being a glabella.
More rocks that many people might not even bother noticing. But this is the trick with these rocks: anything that has a chance to be complete will be under a few thin (but tough) layers. Since the whole trilobite is covered in tubercles, any time I see a few tubercles isolated across the surface, that suggest the possibility that it could very well turn out to be impressive.
I suspect this is showing a glabella and a right cheek. With close inspection, one can make out that the tubercles appear at a few places on the surface, again suggesting a much more complete piece underneath the matrix.
These are not small trilobites, so the rocks one brings back will not be small. Be prepared to fill a bucket very fast. In this broken rock, at the top appears to be an outline. Ventral? Eroded?
Here is a lateral view of the break in the rock, the lower piece. Note the jagged line in the middle. That is the continuation of the trilobite. This will likely be a horribly difficult prep where at some point both halves will be glued together after I determine the orientation (ventral or dorsal). The obvious question might be, "why not trim a bit in the field and separate the overlying matrix from that line?" Absolutely not. The nature of this rock does not allow for that kind of easy separation; instead, going that route will just destroy the specimen.
The trick to finding good Terry specimens in this material is to look for traces on the surface and lines on the side, taking home the most promising pieces to be worked on in the lab with a scribe, abrasion, and eons of patience. Given the high percentage of hard chert, splitting these rocks is going to yield virtually nothing but disappointment or heartbreak. Anything good will shatter right through due to the chert that comes apart in jointed blocks and not clean bedding planes.
Do I have a nearly complete specimen in the last big rock? I won't know for a while. Unlike much easier formations and lithologies, one cannot just rely on clean splits or what is obvious. With this material, you have to take chances and bring what may be promising home for further work.
Spent overnight at the Bois Blanc Formation site with a great field comrade. The focus this time was less on the arenaceous hardground, and more on the hummocky material. Although, to be fair, we were fairly systematic in our sweep. Overall, we made out pretty well, and on at least one register, pretty damn amazing. So, on to the report...
This shows the big difference between the two lithologies. On the left is a giant rugose coral in the hummocky material, and on the right is a tabulate on the arenaceous hardground.
I don't get into the habit of picking up corals, but these were small and interesting enough to find their way into my pocket.
Calymene platys occur occasionally in this material, and usually their only announcement is as an outline on the edge of the rock. In most cases, if you can see the outline, it means much of it is already worn away. The specimen at the bottom does continue into the rock, so there is hope it may be complete, even if there is almost no way of preserving that flaky shell in the process. This material can be tough and sticky at the same time.
A small Burtonops cristata that appears to be complete. I've put it under the scribe briefly, and I haven't got as far to see if the pygidium is there, but the remainder of the thorax appears to be.
And now for what was truly exciting, but may not appear so thrilling in photos. We encountered material where there seemed to be a concentration of Terataspis grandis fragments, suggestive of a moulting ground or tidal sorting. Some rocks were so filled with fragments that it was like they were just layered right on top of each other. Nothing complete, but some good parts, including a glabella.
To most people, these would just look like a big bunch of rocks with a few blackish bits, but throughout and buried in the matrix are the telltale pustular signs of the giant lichid. It will require a good deal of time and patience in the prep lab to get this up to par. The shell is flaky, but there are intervals where they are quite robust and inflated in the matrix. The evidence of them was so ridiculously abundant that we only took the best pieces home. Not many trilobite collectors can say they even have the tiniest fragment of this species, and so we were definitely spoiled. I'll post an update once I can spend some quality time in the lab with these.
UPDATE: Just a preliminary abrasion on this piece, before and after. I'm thinking this is a ventral cranidium (maybe... I have no idea). Other pieces I sampled... wow... They seem to just go on and on in the rock, which means I could get some very nice pieces once all is said and done.
And a few more works in progress:
I managed to spend eight hours at my secret Onondaga spot yesterday. I am starting to lose shoreline as the water levels rise, which is not great in terms of short term collecting as it means only exposing material above the highest watermark which is brutally hard. However, it is good in the long term as it may soften up a few more rocks when they are submerged, making splitting more of a joy when the waters subside again, likely in autumn. But there was still enough material to play with yesterday.
Brachiopods are by far the most abundant fauna in this material. The big, round globular kind leave huge globular divots in the impression side of the bedding plane.
Rostroconch seem to be following me around this year. I still pocket the smaller brachs pictured at the bottom if they are matrix-free and possess both valves.
Here is a monster-conch. 4.5 cm wide, or nearly 2 inches. I was able to free most of it from the matrix. The upper portion comes off like a lid so that one could see the detailed structure inside.
Coronura fragments, and this is not even all of them. Some I even left in the field. It is immensely frustrating to go through so much volume of rock and never find much more than this intact.
Odontocephalus cephalic denticle brims.
This is where the revision part comes in. I've been casually assuming all this time that these were Anchiopsis anchiops. Well, hold on there. These are actually likely to be Odontocephalus pygidia.
More to the point, a morphological comparison of an Anchiopsis I found recently at another location, and on the right the Onondaga material. The main differences include width and terminal caudal spine. The former seems obvious here, but the latter was the source of my error. I had thought the pointy tip of the spine was just too delicate, resulting in getting broken, but each of my Onondaga specimens where the spine is present has this notch in place of a pointed tip. Also, note the relative robust width of the base of the spine in relation to the pygidium. Reexamining all of my assumed Anchiopsis bits leads me to the conclusion that this material does not possess this taxon, but that it is in fact Odontocephalus as the only other match among the synphoriinae that has this notched bottom at the end of a longer spine.
And now for the oddball. Just as I can cross off one species from the list at this location, I can add one more. It was getting late in the day, and my eyes were getting as tired as my hammering arm. I nearly tossed this aside as just another Pseudodechenella pygidium but instinct had me look much closer. It was small, so I took a photo and enlarged it to see the tell-tale nodes and pygidial ribs terminating right at the border. Yes, that is a Mystrocephala. It was in the same rock as all the other usual trilobite suspects, but I don't believe it is reported in this material, relegated as it is to the Amherstburg. This is yet another mystery that underlines the need for more sustained research in Ontario trilobites!
A nice time yesterday to head out and make the 1.5 hour drive to the Bois Blanc Fm spot prospected on April 18. Less than a week later, it was essential to give the site more than a 45 minute once-over. The site itself is a good mix of a lot of Bois Blanc Fm material, including natural outcrops and the stuff ripped out of those that are in nice, tidy piles of about 5 metres high by 10 metres wide, and spanning about 60 metres long. There are also more than one outcrop, and more than one rock pile.
There are roughly two main types of strata.
The first is the wavy, bumpy, lumpy calcareous material that weathers blue-grey like Verulam Fm limestone. This material contains abundant rugose corals (some of them human arm-sized!), crinoids, platycerid gastropods (some of them real monsters), bryozoans, and broken bits of Burtonops. The calcareous stuff is only superficial, as it is just mudflows. In the meat of the rock sandwich is abundant, crystalline chert and quartz.
The second type has arenaceous surfaces that weather to expose a lot of massive coral colonies (tabulate, rugose, pipe, etc.), but underneath which are very fine-grained, mostly blank intervals. Bedding planes, where they exist, do not follow around fossils. IN other words, splitting will more than likely shatter through anything viable. This rock is very tough -- perhaps the toughest on par with Dundee Fm -- and Ludvigsen's statement of it being "perversely" so is accurate. There is no sense bashing into the harder material where the bugs are without having some evidence that something is inside -- a trace hairline, for example. Most of the rocks will split blank or with bits, and is a real time commitment.
What was odd about these rocks was the rarity of brachiopods That is not something I am used to in the Devonian. Also, these intervals had virtually no chert nodules.
If the shell had been complete on this one, it would have come home with me. This is an example of one of those giant platycerid gastropods. In this case, a very long lived one.
This one I did keep, despite missing some shell. All of these are more intact and larger than the ones I find in the Hungry Hollow Member at Arkona.
Plenty of examples of the arenaceous, sandy surfaces. And, not by far, the only or best examples either.
Not much comes out small in the lower Devonian! Anyhow, on to talk about the bugs
Anchiopsis are fairly typical inhabitants of Bois Blanc material, but they were not exactly numerous. In most cases, when they did appear in the calcareous material, there were broken and eroded almost to the point of non-recognition; on the arenaceous surfaces, they would take on the pitted, eroded appearance as seen here. I encountered bits of Burtonops and the impression of a Crassiproetus -- neither species examples I took home.
This one floored me. It is new to the collection: Calymene platys. Sadly, the top of the glabella was sheared off by forces long ago. Still, it is a substantially sized and robust specimen. It is very similar to the Moroccan Flexicalymene ouzregui, and just like Moroccan Devonian material, it is nigh impossible to split this rock without shattering through a bug. I will have to glue the head here, and then prep it a bit.
You can see how robust the bug is at the top of this picture. The skin is missing, but I collected the impression where the skin stuck. That will be a tough prep job.
Have a guess what this is. No, not a gastropod. I'll reveal its identity by the end of this blog post.
Some Calymene partials, and stuff I put in my pocket as the day went on. Those Pleurodictyum at the bottom are quite large!
Now what is this? It comes from the same mystery species as above. It is indeed most of the left genal spine of a Terataspis grandis.
The modified illustration above indicates where it would be placed. This fragment would have belonged to an individual of about 400 mm in length. Hardly the biggest (which would top out around 600 mm), but definitely a find to be proud of. This, and the other fragment, makes two examples in a day.
This has already been an incredible season, and it is still just shy of 50 days in. My checklist of Devonian trilobites is steadily filling out -- and I've still not visited Arkona yet this year. My 2020 goal of laser-focusing on Ontario trilobites has been paying off well. Now that much of the Devonian is "done," what remains are repeat visits to obtain more complete and better specimens, and to go a bit farther afield to prospect some Silurian and Ordovician spots.
I spent four hours Monday at my nearby spot with the Amherstburg and Lucas Fm material, and likely split the last remaining viable rocks in the former that could potentially have bugs. The rest is pretty much stromatoporoidal Lucas Fm trash.
A really sad split. This would have been a fairly good sized Trypaulites sp. pygidium, but it just wasn't worth taking home. And so ends what was once a very productive location. I hoovered it well, draining it of its bugs. There may be some stragglers in some of the harder, more blank material, so it will remain my site of last resort. It lasted for well over 100 visits, and it has been very kind to me in giving up 7 different species of trilobite, 3 of which were new to my collection, and 2 of those being exceptionally rare lichids, and one dalmanitid that has never been reported in Ontario rocks. I never found anything complete, but I came close twice. The Devonian in Ontario is a big tease.
I'm fairly thorough and persistent, and so can say I've emptied two honey holes in my immediate vicinity. But a new one cropped up today. I've been meaning to have a look-see at this very large location for a while. It is certainly filled with layers upon layers of sand alternating with water-worn rock that spans the lower to middle Devonian, interspersed with lots of igneous and metamorphic gumbo. At a depth of about 300-500 feet, it is steady waves of glacial backwash. You'd likely have to dig a mile to hit bedrock in this town.
Devonian formations present include Bois Blanc, Onondaga, Dundee, and even some paper shale filled with Leiorhynchus that you find in the Hungry Hollow Member in Arkona. I started finding pretty sad Eldredgeops rana bits, but that was a sign of more to come. This was only meant to be a quick recon, but this place is massive and takes a while to traverse.
To the highlights, then...
This is the only E. rana I picked up and will show here. Why, because it's a roan red rana, that's why. This appeared in some Dundee material that is just littered with tiny red brachs all the way through, like the rock is infested with fat mites. The same process of mineralization that turned them red seemed to have worked its magic on this pygidium.
This battered bug bit is not even worth focusing the camera on. If, as my field comrade Kevin says, E. rana is the cockroach of the Devonian, Pseudodechenella may be a close contender for that title. Both of these have a very long stratigraphic range. No, I didn't take this one home.
Now this is where I get excited. Dalmanitids. These are not bad at all in terms of preservation, and possibly a bit better than how they come out in the material at my secret Onondaga spot. These both came out of the same rock. In fact, all the following Anchiopsis anchiops were found in it. This was truly a good rock that seemed to be a moulting ground.
The tails come paired with heads. The one on the left is sadly just an impression. The one on the right is likely complete, and I just need to do some cleaning and light scribing to reveal it in full. I've never found a full cephalon of this species before.
More bits and pieces.
No, it is not a fossilized chihuahua head, but an impendent hypostome belonging to Anchiopsis anchiops. This is the better of the two I found. This was a great rock. If I could find a lot more of it, I would be splitting all day.
And what is that pustular bit in the centre? Likely a Coronura bit, so make that species number four at this location.
So that was a nice three hours of exploring. I do plan on going back, of course, and it's nice to add another hot spot to the prospect list. I am hopeful my new backpack comes soon as I'm not sure if my current one will hold up for another adventure. Although my tactical pack is barely a year old, it is torn in a lot of places, and the straps have had to be tied and knotted to other hoops and loops several times. It doesn't help that I carry around about 30 or so pounds of tools in it, and then add another 20 pounds of rock. The thing was bulging at the seams, threatening to burst. Not what you want to have happen in the field, far away from home.
Site knowledge: it's a Devonian buffet. There is no sense in creating a trilobite list associated with the stratigraphy because the rocks are transport erratics from all over.
In other fossil news, I have created a fantastic prospecting field document for Silurian trilobites of Ontario, and am eager to get on the road to trial its effectiveness. Obviously I won't post that here unless my goal was to ensure others would scoop up everything first. But, a few of my field comrades will hopefully benefit.
Tomorrow looks like a rainy, ice-pellety day. A good one to do a bit of prep. On Friday it is back to my secret Bois Blanc spot to do a whole day's work. Stay tuned!
Yesterday was a good day to get out and prospect, what with the nice weather and the fact that the flora hasn't grown in yet (just some budding on the underbrush). So off we went to check on a lead I got back in November, to a spot atop the Niagara escarpment. My maps indicated that the material would be Silurian in age. To my great and utter shame (or from lack of opportunity), I have yet to find any Silurian trilobites in Ontario. That being said, Silurian outcrops represent a narrow band in southwestern Ontario, with much of it being blank evaporites, anhydrites indicative of salt which is mined (yes, we have salt mines -- a perfect place to send one's children!).
The site was an abandoned quarry where the main pit was flooded some many decades ago. The exposures were apparent, and mostly around the fake lake, running the circumference (probably a good 500-750 metres) and a depth from top to waterline of about 3-5 metres. The first thing was to check each interval along the strata. Here is just a small section of the exposed stepped wall:
A lot going on. Some layers were more blocky and massive, others were thin and seemingly calcareous. But whether they were thick or thin, they were almost entirely blank with some tough, dense tiny mineralization when split. It looks a lot more promising than it actually is. Lumpy, muddy, and blank with only a few tiny brachiopods on very rare occasion, and some burrows, and pretty tough to break cleanly. But that is the Silurian for you: plenty of largely blank layers from less than ideal deposition and preservation. There are some layers in the Silurian here that are exceptional; this was not one of them!
From the sensational Silurian! This was my major haul from probing those layers. Muddy little brachs. Well, live and learn! So off we went to do a site-seeing stop.
The Devil's Punchbowl's stratigraphic range, oldest to youngest, would be Queenston Fm (upper Ordovician) to the Lockport Fm (middle Silurian). It's a conservation area, so any excavation would be quite illegal. So, it's a take photos, leave footprints visit.
Here's a nice view of the Lockport Fm that caps much of the escarpment. Both the Ancaster and Gasport Members are shown here. Buried beneath my feet would be the coveted Rochester Fm shale, home of the great Silurian trilobites. Sigh.
There are fossils in it, of course. In the ceiling of a small cavern, a nautiloid impression. Lots of nature to see, and likely a place we'll visit later in the year by hitting the paths. So off we went to hit up one more location before heading home. This time, it was an engagement in younger rocks: the lower Devonian, Bois Blanc Fm.
The photograph washes the colour out a bit, but there is the tell-tale blue chert of the Bois Blanc Fm. We arrived at the area, at which point I got out of the car and did a very quick field scan. It was not the ideal spot to start digging, so we opted to go on a bit farther to find a better outcrop with a different faunal constituency and composition ratio. Prospecting is serious work, well beyond the weekend warrior's penchant for, say, just going to fossil parks and breaking a few small rocks with a mallet!
There are layers in the Bois Blanc that are just choked with corals, forming considerable reef systems and bioherms. The rocks here are not terribly ideal for faunal diversity, and so I'm moving on...
Now here we go. Yes, there will still be corals blocking the view, but these layers are a thinner, blue-grey, highly calcareous shale that splits nice and easy. It has the same colour and consistency as the Verulam Formation, and the similar issue of not always being able to make out the fossils from the matrix when freshly split as opposed to weathered. In the shot above, what appears to be a crinoid head is rolling along with a toppled rugose coral.
Aha! Bingo. There's not much left to the trilobite pygidium here, but I have an eye for trilobitic shell material. Only the margin is preserved here with the underlying coral poking through. This was all the evidence I needed to get cracking into this layer. I knew there would be bugs, but the question remains as to what will result in the best return on investment in each layer?
A much more definitively diagnostic trilobite tail. Just as a refresher, the (work in progress) list of trilobites in the Bois Blanc include the following:
?Dalmanites comis (Hall & Clarke)
? Dalmanites phacoptyx
?[Kettneraspis] callicera [The Acidaspis of Hall & Clarke]
Pseudodechenella sp. aff. clara
Pseudodechenella sp. aff. nodosa
Note that the only phacopidae in the group is Burtonops cristata. There is a species with less microsculpture (Viaphacops pipa) that I need to add to the list here. So, let's settle the difference and call it Burtonops sp. -- At least for now. As a small sidenote, these two species were once Phacops cristata and Phacops pipa (and before that, Phacops cristatus var. pipa). Well, once all the Phacops of eastern North America were taonomically reclassified so that Phacops does not apply here as they do in Morocco, names were changed (for example, Phacops rana = Eldredgeops rana). And so these very, very similar species got split into two genera: Burtonops and Viaphacops. Confused yet?
Another Burt the Bug, this one enrolled and crushed to show the anterior/ventral side. This shale is fragile in spots, which is good to know when it comes to likely preservation (and the need to keep the field kit well-stocked in super glue). That horn-like feature to the left? Not quite sure what it is. I have some ideas that range from the banal to the wishful.
So not a bad outing at all. It began as a failed prospect and turned into something very promising. I only spent 45 minutes at this new spot, and there is a good amount of material to get through. There is some urgency, though: the spot is slated for development and will be buried under houses as soon as construction projects are given the green light to resume. It means I need to hope for the grand trifecta of time, weather, and opportunity to make the most of the spot before it is gone forever.
And this also makes the 40th day of the 2020 season. Out of three slated prospect areas, only one was viable, but batting .333 is not bad at all given that prospecting new sites usually has a success rate of about 1 out of 10. I've also encountered one other site by accident (the Onondaga stuff). So far, I've visited 6 spots total, 4 of which are viable. I haven't even been to Arkona yet this year! This is pretty good given that the borders are shut tight, and it is doubtful that our one last quarry in the Ordovician will be letting us in this spring.
Of course, this is just the first few steps into an adventure that may see me in much longer, sustained periods of prospecting, farther from home. As always, I'll keep this place updated when I can.
Spent another four hours at the new site, mostly probing the rocks and getting a feel for which layers will be the most gainful. There are some rocks that are just so filled with large brachiopods at the expense of anything else (except maybe a few Pseudodechenella sp. pygidia), and others that are almost all rostroconchs.
This image and the closeup gives some indication of the typical beds that come out, sheet after sheet, of almost exclusively brachiopods of mostly decent size.
Some of these rostroconchs attained to a fairly robust size. All but the specimen on the right popped out of the matrix. I neglected to take a photo of a few layers where they were so numerous that they were stacking on top of each other. What the size and abundance of these confirms for me is that the deposition environment was shallow, turbulent, and open marine. Some rostroconchs could attain a length of 15 cm.
This I bucketed earlier in the day, and were not the biggest I encountered.
Gastropod steinkerns. Some could be fairly substantial in size, but extracting them from the host rock when they are of any decent size is a major difficulty.
These brachiopods are quite large and plump. The photo does not convey their rotund aspect very well, but picture crabapples or large kiwis.
Not as big on the bugs this trip (discounting the zillions of small Pseudodechenella tails!). Two fragments of Odontocephalus sp. The one on the right is an impression, but shows the eye and a bit of cheek. This genus is particularly hardy, and was able to persist in some less than hospitable environments that other bugs could not tolerate.
Anchiops anchiopsis tails. The piece with the double initially appeared as four on the same undulating plane adjacent to a plane that was very jointed. Sadly, the other two were in pretty poor shape and not worth bringing home.
I'm not done yet. I hope to get out again very soon and so a solid day's work on this stuff.
Prospecting for new sites can be a miserable business, with a failure to success ratio of ten to one. But, it is that one spot that makes the memories of all those disappointments vanish. Today was one of those days after getting skunked twice on dead leads. Of course, for obvious reasons I can't disclose the location. But keep reading as I save the best for last.
This material is plentiful, filled with sometimes more brachiopods than matrix, some bryozoans, tons of rostroconchs, and some high-spired gastropod steinkerns This seems to be classic Onandaga material.
Just riddled with fossils, mostly brachs. This material breaks apart fairly easily, in chunks or along uneven bedding planes, similar to the Formosa Reef material.
These are absolute beasts! I'm not a brach collector, but these big brutes had to come home with me. The one on the farthest right has a "wingspan" of about 8 cm.
Some people claim that rostroconchs are rare; I'm up to my back teeth in the things.
But let's get to my favourite part: the bugs! Now, keep in mind that there are thousands upon thousands of rocks at my new spot, and I only managed to get through a single slab that was about a metre wide, metre long, and 50 or so cm thick. In that rock I managed to pull four different species of trilobites. Nothing complete, but that is still pretty expletive amazing for Devonian rocks.
First two. On the top left is a Pseudodechenella. Likely the lower left is a free cheek of one as well. The rocks had an abundance of their moulted bits. In the middle is likely the dalmanitid, Anchiopsis anchiops, and a much better example with the pygidial spike (still partially buried under matrix) is on the right.
Not one, but two examples of the frontal lobe denticles of Odontocephalus sp. I've found a similar example a few years back in dumped fill near my house, but these are a lot nicer.
This was my trip-maker: a pygidium of Coronura aspectans. Note the spokes coming out of the pydigidal margin.
Did I mention that all of these were in the same rock? Wow.
Here's a snip from Lesperance and Bourque's paper on the synphoriinae. I've put big green checkmarks on the ones I found today. Again, in the same rock.
So, yeah, I think I'll be going back to that spot. Chances of finding anything complete is very low, but I'd be pretty jazzed about finding more examples of the Coronura.
I'll close out today's post with my newest doodle. Next up is a Damesella paronai.
How niche a topic can I make it? Yes, today's post is about hypostomes, and more particularly, the hypostomes of lichid trilobites (of the Amherstburg Formation).
Ever since stumbling upon my Amherstburg fill area back in August, I've certainly been fortunate to crack open many a rock to find the occasional fragments of lichids, from isolated pygidia, cranidia, librigena, and even a connected thorax (just the one time, recently). and hypostomes.
The thing about hypostomes is that they are very easy to miss for a lot of collectors in the field. They don't look trilobitic to anyone who isn't already familiar with the ventral morphology of a trilobite. When I first started several years ago, I probably left dozens of them in the field. There has been much discussion and speculation on the purpose of this hard, plate that appears just underneath the cephalon, and just as much variety in morphology (check out the spooky and fierce-looking Hypodicranotus hypostome in Ludvigsen's paper here!). It is generally agreed that they served a primary purpose as part of their feeding apparatus. On that discussion, I highly recommend Hegna, T.A. (2010) The function of forks: Isotelus-type hypostomes and trilobite feeding. Lethaia, Vol. 43, pp. 411–419.
This snip of four line drawing representative lichid hypstomes is from page 188 of the lichid bible, Thomas, A.T., and Holloway D.J. (1988). Classification and Phylogeny of the Trilobite Order Lichida Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, Vol. 321, No. 1205 (Aug. 26, 1988), pp. 179-262. There are similarities among the genera's conterminant hypostomes, but also distinct differences as seen above.
At present, I have been able to reasonably identify three lichid genera from this material: Acanthopyge contusa, Echinolichas eriopis, and Echinolichas sp. cp. hispidus. These are consistent with equivalent strata in New York (see Whiteley, Kloc, and Brett's Trilobites of New York, or "TONY" among us bug enthusiasts).
Here are three hypostomes I have found since autumn of last year, with the one on the far right being a recent (as of today) find. I would guess that the first hypostome belongs to an echinolichine, whereas the middle one is unmistakably Acanthopgye contusa. The third one is still undetermined to me as of yet. It seems to share the echinolichine shape, and yet also appears to possess the granular ornamentation of the Acanthopyge. It is also by far the largest one I've found, with a width of just under 20 mm. That would possibly make the original owner between about 70-100 mm in length. Not excessively large, but not tiny. Of course, the preservation could be much better on the last two, but I take what the rock will give.
Hopefully in future posts about the lichids I can start organizing some of the other body parts, too.
Been moving tons of rock the last few days -- quite literally, in fact. I call it training for when society collapses and we're thrust into the world of Mad Max. Not quite, but it has been nice to get out and dig more. Here is a sequence of events of removing a single big rock:
Fun times! And what was in all that rock? Nothing much! Them's the breaks sometimes. The thing about this material is that you never know. It could look promising on the outside and along the visible edges, or it may be blank, but what is inside can only be determined by actually breaking into it. This rock was wide and very deep. It was also wedged and jammed in by every other rock, which in turn was wedged and jammed in by other rocks, ad infinitum. Sometimes the rock wiggles like a loose tooth, but just won't give.
So, any finds from my spot for all those many hours? I've bagged a few more lichid fragments (one of which was a real heartbreaker as it was the edge of an exquisitely preserved pygidium with all the pustules, but it started just before the edge of where the rock stopped. Argh! A number of very wee Mystrocephala stummi pygidia, the usual pygidial/genal/thoracic/cranidia assortment of Pseudodechenella sp. and Crassiproetus crassimarginatus that I'm leaving in the field. But here's something pretty:
A rostroconch (Conocardium cuneus). Rare as all git-out everywhere else but here. At this spot, I'm up to my back teeth in these things, spanning in size from a few millimetres up to 10 centimetres. Both the Amherstburg and Lucas Fm rocks at this location are well stocked with them. If nothing else could survive in the environment, or preserve well, these would.
And now for something ugly:
It's a complete Pseudodechenella sp. -- complete if we mean missing a tail and its cheeks. There's a bit more under the matrix, but not that much more. I might be able to expose the other side of the thorax at best. This one was lodged in a massive block buried several feet deep with only the top showing. Oh, and forget about reliable bedding planes. For the added challenge, it will appear on a rounded bump on the edge of the rock. Extraction was a bit nervy on this one, and it still shattered off a bit -- and that's why I carry super glue in the field for this kind of battlefield medicine.
I will likely make a few more trips to this spot even if the gains are minimal. I'm just biding time until Deb is free so we can get out collecting at a few other spots I need to check. We're also getting a new car (well, used, but a newer model with really low mileage), so it should hopefully not cack out when we're en route to somewhere like, say, Bowmanville for a dig that is now much harder to join up with these days. Losing my spot last October was really depressing.
I don't foresee any new updates this week unless I come away with something amazing. Most of the other stuff -- not pictured -- is just the same old stuff. Finding a complete trilobite in this stuff is about as likely as finding an intact strawberry in your daiquiri, such is the nature of the facies. It won't stop me trying to beat the odds of this Devonian casino in trying to find that mystical, complete lichid.
Since my MMA classes are canceled for the next few weeks, I might be able to get caught up on my trilobite drawings... I have a Damesella and a Metapolichas in the queue, but both are pustulose which equals beaucoup time to render.
More notes from the Devonian underground soon...