Since my last post, Covid-19 has become even more serious. I've been keeping busy and getting on top of grading final papers. Of course, I also took the opportunity to get out as much as possible. So this post will be a triple update: finds, a purchase, and a drawing.
The first trip was to locate the source of my Amherstburg Fm material. We may have found it, but there were no natural outcrops. The closest was in enormous pits behind barbed wire fences and no trespassing signs -- in other words, a zero-access quarry. So, I fell back on my usual spot in search of more trilo-bits.
Some stuff I wasn't looking for. A large gastropod steinkern on the left, and a big brach and bivalve on the right.
Yes, large and very cool rostroconchs, but I'm getting a bit sick of them!
Left: looks to be part of a Trypaulites sp., and the most complete I've found. Lucky me that it stops right at the natural edge of the rock.
Right: bookend pygidia of Mystrocephala and Pseudodechenella.
And even more Mystrocephala. Preservation is pretty poor.
Lichid pygidia. The one on the left is too damaged to make out. It could be Acanthopyge or Echinolichas. The one on the right is definitely Echinolichas. I lost the positive due to the nature of this material's tendency to explode.
Hypostomes! On the left is likely an echinolichine, and the one on the right is a beat up Acanthopyge contusa on account of its shape and pustular ornamentation.
Although I was skunked on my attempt to dig through the source of my Devonian material, I at least came home to my first harpetid in the mail. Not the best preservation and prep for this Harpes perradiatus from the Devonian of Morocco, but pretty good given the price I paid.
And, as promised, a new drawing. I have about four more queued up, but they will take eons to complete as they are all ridiculously complicated... and my carpal tunnel is dogging me.
Hopefully I'll be able to get out a bit next week once the rains are done, assuming they don't put us on lockdown and home confinement. I do have some trilobite-related stuff to do around the house if that happens.
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...
Well, now that it's the apocalypse, what better thing to do but avoid the drummed-up panic of the masses and go out for some bug hunting? A great thing about fossil collecting is that the chance of contracting the coronavirus from the Devonian is infinitesimally small. As my university has canceled classes in preparation to move everything online, it sees me with some free collecting time. Of course, I'll be revising my materials to be digitally migrated, and undergoing the final big wave of grading, but I may be able to sneak away a bit more often.
Today was another visit to my Amherstburg/Lucas Fm site. A lot of rock was split, almost all of it massive armour stone frustratingly rooted deep under every other rock. For all the rock split, just about none of it was of any interest to me -- just the same old, same old.
In the image above, I've already popped off the cap of this armour stone. Well, actually, it was a lot of digging, and then driving the chisel with the sledge for eons until all my bones rattled. There were a few traces of proetids amidst the usual coral clutter, brach bumpf, and bryozoan bunches. So, nothing really worth keeping. A few neat gastropods were encountered (a platycerid, and a high-spired steinkern in the chert of another rock). But the real find to make this post worthwhile...
Although a bit in rough shape, this is 2.5 cm of lichid. More importantly, is that it is a lichid with both pygidium and thoracic segments. Equally important, perhaps, is this is likely an Echinolichas sp (cf. eriopis). In Ontario. Two-thirds complete. There's a bit more hiding underneath the matrix. I doubt it will have its head, but -- who knows? I almost didn't see it as it blended right into the background matrix. To the best of my knowledge, I don't think a 2/3 complete and intact example of this species has ever been found.
Definitely a trip-maker. Got to find all the amazing lichids during the end of the world!
UPDATE: As a fellow trilobite expert pointed out to me yesterday, if it lacks the medial axial spine, then it may be a much better match with Echinolichas hispidus as opposed to E. eriopis. Here on the left is the illustration in Hall and Clarke (1888) matched with the photos of my specimen (thanks to S.M. for the stitching!), and on the right is a photo of the holotype (NYSM 4553) in Thomas and Holloway (1988).
In E. hispidus, in place of the large spine is little more than a basal bump. Of course, given the poor condition of this specimen it cannot be stated with great certainty that this belongs to one species or the other. After some light scribing to reveal more of the pygidium, I am leaving it be until I can get it in better hands to reveal more.
As it is so faint and blends with the matrix, I have experimented with different lighting as well as creating a negative in the hopes of sussing out more diagnostic details. This will be a study piece for the time being!
To recap, this is certainly rareness factor 3: firstly, a Devonian lichid in Ontario, even as a fragment, is quite rare as only two species are officially reported and confirmed in the Formosa Reef and the Bois Blanc Fm (with some questions of others having been cited by Stauffer in 1915); secondly, it is exceedingly rare to find a specimen here where it is not just an isolated pygidium or cranidium, but a pygidium with its connected thorax (those tend to disarticulate quickly); thirdly, a species not actually reported in Ontario rocks (but in corresponding NY rocks).
Image credits (and further reading):
Hall, J. and 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
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
So it begins!
I still have a little over three weeks on campus, but the surprise of early spring weather means rolling in the start of the collecting season.
This year is going to be carried out a bit differently.
I'll be conducting systematic prospecting and fieldwork, which means exploring new areas and visiting long neglected sites. My fieldnotes identify several potential spots for site visits. Much of my travels will keep me focused on Ontario, and will be trained on trilobites. I have spots that span the Ordovician, Silurian, and Devonian that should hopefully result in some spectacular finds this year.
My other side goal is to continue adding to my field guide to Devonian trilobites of Ontario. To that end, I will need to explore more spots where Devonian rocks outcrop, which is not all that common in Ontario given that glacial drift is like a blanket that is about 30 - 400 feet thick in most places.
My first stop of the spring was just nearby where Amherstburg and Lucas Fm fill has captured my attention since August of last year.
On Saturday and Sunday, temperatures were hitting close to the mid-teens. Still, it takes a while longer for the snow to burn off. I set out around sunrise through the woods and to the fill area. The bonus of leaving while the temperature is still below freezing is that the mud is still frozen. It is not so great on site, however, as the rocks can be frozen together and in the ground. But that is what tools are for!
Let's dig in. Most of those rocks are rubbish. The focus is on the brownish-grey ones with bituminous streaks and lenticular coral showing. The other types of rock are generally blank or sandy/leached with mostly tiny rostroconch and crappy gastropod steinkerns. The chocolate brown rocks can be busy with bryozoans and brachs (a good sign) or muddy blanks -- you never know until you wrestle them out and try splitting them. Forget about bedding planes in many cases, or cooperative rocks that will split nicely. Some of these are brutally hard and tend to shatter. The other type of gainful rock tends to be whitish-grey and busy with well sorted smaller skeletal material. Both of these kinds of rock are reef rubble or lagoon. I don't bother with the very crumbly peritidal stuff.
A decent sized gastropod. I keep these for other people, and to record associated fauna with the trilobites.
Fairly typical fauna for this formation -- bryozoans and a few brachs. Nothing I'd take home, but anyone I take out to this spot is welcome to them.
Some pretty unremarkable lichid fragments (top two, and the lower left). I keep them for completion's sake, and lichids are generally rare anyway, and that includes fragments. The lower right is likely a Mystrocephala stummi. They are very tiny (0.3-0.7 cm wide) and quite easy to miss.
More lichid frags...
Plenty of Crassiproetus pygidia, and this platycerid.
Not that I want to jinx anything, but it looks like we have a few weeks of mild weather to look forward to, with possibly Sunday my first post-winter return to the field. It will be another engagement with the Amherstburg Fm material, but I have been quietly developing plans for new prospects.
In trilobite news, with the very recent publication of Bignon et al.'s paper, there are now 14 Orders of trilobites:
Agnostida SALTER 1864
Asaphida SALTER 1864
Aulacopleurida ADRAIN 2011
Corynexochida KOBAYASHI 1934
Eodiscida KOBAYASHI 1939
Harpetida WHITTINGTON 1959
Lichida MOORE 1959
Odontopleurida WHITTINGTON 1959
Olenida ADRAIN 2011
Phacopida SALTER 1864
Proetida FORTEY & OWENS 1975
Ptychopariida SWINNERTON 1915
Redlichiida RICHTER 1932
Trinucleida BIGNON et al 2020**
The Trinucleida were once a superfamily in the Asaphida, but have now been elevated to full Order status. And, to be honest, comparing the appearance of Trinucleids and Asaphids, they seemed an odd match insofar as they appear to differ more than they appear similar. All that being said, I'll need to revise my trilobite gallery to reflect this (and about three other Orders I've been too absent-minded to add) -- something for a rainy day. For now, another drawing:
I also experimented with some mid-tone paper, but just a really quick sketch:
So that one is just a draft for now, flagged for redoing it properly.
And this Moroccan phacopid came in the mail. I actually did not have an example of Zlichovaspis rugosa, and the price was too good to pass up. The quick snap of the bug hardly does it justice in terms of its impressive size. This is not a premium prepared bug -- visible scribe marks and a coating to hide a few mistakes is pretty customary for a B-grade bug, but even those can command high prices. In this case, I got it for a very good deal.
I am just more excited at the moment about getting back out into the field. The snows are quickly receding. I've been digging into Stauffer's 1915 text on the section featuring the Amherstburg/Onandaga material, which seems to be the most comprehensive I've seen in terms of a faunal list (albeit a number of those taxonomic designations have been revised significantly!). And, with just four more weeks of classes, serious field time cometh! Hopefully I'll make out okay this Sunday to post some finds. Until then...