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
I've spent many days over the last two weeks scouring my new local site. I've pored over the literature and attempted to do a systematic analysis of the fauna in each of the rock types, taking extensive field notes. In terms of finds, not counting the numerous Crassiproetus pygidia and Pseudodechenella pygidia and cheeks, there are more days I go home empty-handed rather than dancing on air.
On the third consecutive day at this site, I managed to locate the right type of rock that is generally highly fossiliferous. This type of rock is in a minority at this site, and I've already split through any of the visible examples, leading me to dig under other large rocks in the hopes of finding more of the "good stuff."
The trilobites almost exclusively appear in rocks that contain large fenestrate bryozoans. The environment was shallow marine reef (owing to the massive presence of reef-builders).
Here is Echinolichas sp. fragment number two:
I collected the positive and the impression. It is in pretty rough shape, but any fragment of this lichid will come home with me. So is the matter settled about the strata being Bois Blanc? Hold on. Also in the same rock was this:
The top image is a capture from Rolf Ludvigsen's Fossils of Ontario Part 1: The Trilobites, and it shows a cephalon of the lichid Acanthopyge contusa. The image below is my find. But this is reported in the Amherstburg / Formosa Reef. This was already a bit confusing!
Terataspis is only reported in the Bois Blanc Fm. If this were Bois Blanc material, I have not seen even a trace of Anchiopsis in the large volume of material I've gone through. Acanthopyge is only reported in the Amherstburg, and although volumetrically the abundance of Crassiproetus is indicative of this formation, it is also a poor index given that it prevailed across several strata.
Riddles upon riddles aside, I am happy to welcome my second Terataspis, and a brand new lichid to my collection!
Stay tuned, for there is still a very large source rock for me to break down that weighs in excess of a metric ton. It is where the Terataspis was found. More to come this week, I hope!
Update, Sept 18, 2019
I found a second cephalon example of Acanthopyge contusa: