A short post today before I'm off for three days at three different quarries.
So I spent the latter half of the morning at my usual spot just beyond my backyard, cracking rocks in the rip rap pit. There is a wide variety of formations present, all of them in a big jumble. I do know that they largely span the early to mid Devonian. I was not expecting to find much as I've been there so many times that it has become the victim of my picking it over! However, surprises still happen on occasion.
A new entry to be included in the trilobite gallery. Initially, I thought this was just another Anchiopsis anchiops, as their tail fragments are among those I find on occasion in these rocks. But it is not quite right. These are images from Rolf Ludvigsen's 1979 book, Fossils of Ontario: The Trilobites. The one on the right is the closer match: Coronura aspectans, which is found in the Dundee Fm.
.How I can suspect it is Coronura is based on a few observations: 1. The pygidium of my specimen does not taper in the same way as an Anchiopsis; 2. The number of pleural pairs is very high; 3. The axial lobe is relatively thin; 4. There seems to be small concavity at the pydigium's edge that would either have been a single spike (no) or the two-pronged spike of a Coronura.
And so, as tentatively confirmed by my TFF friend, Don, I'm going with Coronura aspectans. Awesome!
*****But wait, there's more!*****
Actually, the tentative ID is incorrect. It was tentative, just for the record, based on a poorly preserved specimen. Scott, our trilobite expert on TFF, has given the ID as Trypaulites erinus from the Bois Blanc Fm. Not a new genus for me, but definitely a new species. Here is the picture Scott referenced, put next to another image of my specimen. We have a dead ringer!
So, a few things to mention here. T. erinus is described in "STRATIGRAPHY AND PALEONTOLOGY OF THE SYNPHORIIDAE (LOWER AND MIDDLE DEVONIAN DALMANITACEAN TRILOBITES)" by Pierre Lesperance (thanks again to Scott for the reference, and from where the image above comes).
Second point being that this specimen is only known by its pygidium; no other parts have been found. I suppose there is a chance that this is not a common find.
This year has had a lot of these moments where I seem to find uncommon/rare trilobites for which only fragments are known - or, in some cases, no specimens have been recorded where I found them (but they are described in equivalent units elsewhere). Finding fragments may seem like a bummer, and a lot of fossil collectors would pitch them aside in search of a full specimen, but there are specimens out there so rare that finding a fragment is a significant event.
It looks as though the "rip rap hill/pit" behind my home is a veritable trove of uncommon specimens. And to think, several years ago, I just ignored a lot of the rock there or assumed it was just dull Dundee stuff. I've now found five distinct genera at this location, and I can only hope more rock gets exposed for me to split. At the same time, trilobites are not abundant at this location; many have been the trips when I came back skunked without even a trace of trilobite, and I would say it is now about 1 in 5 trips that I find even a single trace. But I need more weathering and exposure. I am pretty much running out of rock to break, and spending my time sifting through tiny shards of my own previous visits is unlikely to make for a lot more winning visits.