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!
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.
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...