With the long weekend in full swing, I decided to get up early and have a look at the pit/pond just beyond my backyard. Much of it is Bois Blanc and Dundee Fm fill. I've made a lot of posts about the area in the last five years. This time around, I found something new.
I spent some time in a 10 m x 10 m area by the pond, breaking whatever looked promising. I've found some interesting gastropod steinkerns in the past, and this one was no exception.
Trilobite partials to the left, a brachiopod on the right. Typical fare for these lower to mid Devonian rocks.
A nice split with a little bit of everything - mostly brachiopods and one horn coral calyx (the round item).
A high-spired gastropod steinkern (partially buried in matrix) with its impression.
Closeup of a bryozoan.
More trilobite partials (two pygidia impressions and one cephalon impression fragment)
Eldredgeops sp. cephalon fragment.
Believe it or not, this was the major find of the trip. Although it is only about 2.5 cm wide and kind of looks like it could be a fragment of coral, it is indeed a trilobite fragment... but which one?
I also ensured to collect the negative as well. It is a good idea, when in doubt about a specimen, to collect it - and all the other pieces it is associated with!
So to which trilobite does this "toothy" fragment belong? Courtesy of our resident trilobite expert Scott, on The Fossil Forum, the answer can be found here:
Stauffer, C.R. 1915
The Devonian of Southwestern Ontario.
Geological Survey of Canada Memoir, 34:1-341
It is Odontocephalus sp. and as Scott tells me, in the last century or more, this trilobite has only been reported in a few papers from Ontario, thus making this a far from common find! Pictured below is a simplified line illustration of what it looks like complete.
So... that's quite exciting! This site has now yielded up the following trilobites in the last few years:
Odontocephalus sp. (?selenurus)
This figure from Lesperance and Bourque (1971) shows the evolutionary branching from the genus Roncellia. My recent find means that I have representatives of each of the three major synphoriinae branches (Odontocephalus branch, Anchiopsis branch, and Trypaulites branch). What distinguishes them significantly is both the anterior glabellar process/border, but also the pygidial "spike" (or lack thereof). Note here the bifid spine that appears in both Odontocephalus and Coronura.
At this point, I am a bit more confident in assigning this one to the species of O. selenurus given the presence of 9 rather than 11 glabellar denticles as would be found on O. aegeria (which is also not reported to be found outside New York).
According to Stumm (1954), only three fragments of O. selenurus have ever been found in Ontario; the first, by Carl Rominger in 1888, and two by Stauffer in 1915. Assuming no further fragments have since been found, my find would be the first in 103 years, and the fourth in Ontario's paleontological history. This makes this find quite exceptional and rare!
This particular species is cited only a few times, including in Stauffer (1915), Stumm (1954), Lesperance and Bourque (1971), Lesperance (1975), Sanford and Norris (1975), and Ludvigsen (1979).
1. Lesperance, P. (1975) Stratigraphy and Paleopntology of the Syphoriidae (Lower and Middle Devonian Dalmanitacean Trilobites). Journal of Paleontology 49.1: 91-137
2. Lesperance, P. and P.A. Bourque (1971). The Syphoriinae: An Evolutionary Pattern of Lower and Middle Devonian Trilobites. Journal of Paleontology 45.2: 182-208.
3. Ludvigsen, R. Fossils of Ontario: The Trilobites. ROM.
4. Sanford, R.V. and A.W. Norris. (1975). Devonian stratigraphy of the Hudson Platform. Geological Survey of Canada, Memoir 379 I. 1-124; II. 1-248
5. Stumm, E.C. (1954). Lower Middle Devonian Phacopid Trilobites from Michigan, Southwestern Ontario, and the Ohio Valley. Contributions from the Museum of Paleontology, University of Michigan XI.11: 201-21.
6. Stauffer, C.R. (1915). The Devonian of Southwestern Ontario. Geological Survey of Canada Memoir, 34:1-341
Despite some flirtation with the freezing mark the past few days that is looking to put my Friday trip to Arkona on hold, on the whole spring is definitely showing itself. This one is just a short post to highlight some river finds, and show off my newest Russian asaphid. UPDATE: actually, two.
On Monday I went back to the river on campus, remembering this time to bring my trusty rock hammer. There was not much to be had among the dull, plain, river-worn rock and the plentiful limestone only filled with tiny shell hash, but closer to the end of my time there before having to teach, I pulled out these odd beasts. Once I got confirmation of what they were, and that they are somewhat rare, I went back to collect the rest the next morning.
So what are they? I've seen these before and just dismissed them as some kind of wacky brachiopod. Not so! They are somewhat related to bivalves but occupy a place all their own as being rostroconches. These planktic, valved creatures would more resemble a taco than a clam. Their hinges are somewhat weak, and they have a long rostrum (the piece on the far left, centre shows it best - the striations that appear like someone scraped it). Looking at the comparable species in the general strata, it may be a Conocardium cuneus. It is a first for me ... at least the first time I've kept one. It was interesting to learn that finding these is far from common, and yet I pulled all of this from a single rock.
This is another lovely Russian asaphid, the fifth that has arrived in my collection, and with five more to come. This would be a nice, prone Asaphus plautini from the Mid-Ordovician, Aseri Stage, collected from the Gostilitsy Quarry near St Petersburg, Russia. It is about 62 mm long, so about average for this species. Here is the evolutionary sequence chart from thefossilmuseum.net:
But wait, there's more! Today I welcome species #6 to the family, Asaphus kotlukovi:
Last I checked, it's still winter, and that means no possibility of getting out to collect. However, needs must when the devil drives and all that, so I have been doing some collecting indoors.
I am going to kick this post off with something very close to home (as in, at home!).
This pygidium was found among the many pieces I collected from my honey hole in town. When I first found it, I thought little of it and just threw it in the bag. However, now that the snows keep my troublemaking relegated to the indoors, I decided on a Sunday afternoon to look a bit closer at stuff I stuffed into containers from the previous year. This one is bereft of an identity at the moment. I've searched the literature, from Ludvigsen to Lesperance, to Levi-Setti to Whittington, and can't seem to get a proper ID on this lower Devonian trilobite. If anyone out there knows, I'd be grateful to hear from you in the comments.
So, setting aside mysteries, I purchased a few trilobites - one from eBay and two from a fellow forum member.
This is the eBay acquisition that I got very cheaply: a Declivolithus ?alfredi from Morocco. This is a neat looking asaphid trilobite from the Ordovician with a kind of textured "fan" that reminds me of harpetid bugs.
Adding another Moroccan trilobite to the collection (recalling I also have a Drotops megalomanicus acquired in July, 2017), this is an exquisitely well-preserved Hollardops sp. I got from a fellow forum member. The eye lenses show great detail, and I can tell it's genuine as opposed to the many fakes out there because of one very telling detail: notice the crack that travels across the specimen? The first picture shows it best. That is known as a discovery crack, and that is how these trilobites are found in Morocco. The matrix is ridiculously dense, so trilobites do not come out nice and clean. Instead, diggers will find a whisker line that shows the presence of a trilobite. From there, they glue the two pieces together and prep it out. This one looks very similar to Greenops, but this style for phacopids was quite popular in the Devonian!
From Russia with love! Yes, this is an Ordovician trilobite from Russia, Asaphus kowalewskii. It is a commonly sought after specimen due to its long eye stalks, or peduncles. Sadly, despite all noble efforts from my friend on the forum, the postal service still managed to damage this one, so it took an hour of trying to reattach several pieces of the peduncles. They may not be in their proper orientation, but you haven't explored your full lexicon of expletives until you try to use crazy glue and tweezers to try and restore broken peduncles. Despite its current state, it still finds a home here.
These trilobites, for some reason, developed long eye stalks. It has been reasoned that it was to be able to see in highly turbid waters, or to be able to continue their benthic existence safely while being buried up to their eyes. What is particularly unique about them is that they are only found in Russia.
And that isn't all. Yes, wait, there's more! - But that will have to wait until packages arrive. I have traded some spare trilobites with forum members in the Netherlands and South Korea who have some lovely bugs to send me in return. I also have another exotic Moroccan bug coming from England. I'll update this post or make a new one when they all come in.
Apart from that, I did some online shopping for fossil necessities. Coming in the mail will be a pin vice, which will spare my poor hands and fingers in using sewing needles for fine prep. I'm also awaiting a tactical backpack to replace my rather worn backpack that is pretty much unusable now as a cat peed on it.
But, so far, 2018 has seen the arrival of three new species to my collection, and one mystery unknown! I anticipate from between 4-8 new specimens in the next few months. Starting off the collecting year - in pre-season - strongly!
Pictured here is the very inviting forest path that leads to my little honey hole out behind my home. I have to say that this spot has treated me very well this year. Just as I think I've picked it clean and there are no new things to be seen, I get a surprise. No surprises this time, though.
Having spent four years coming back to this place, each year has presented something new. But it is perhaps in this last year that my finds from there have really been great. Back in 2013, I was shocked to find some Eldredgeops rana, but this year I've been able to be more systematic in identifying some of the imported fill by rock type, and direct my efforts accordingly. No fewer than three new trilobite specimens (all partials, sadly, but still interesting) have been logged into my collection: Anchiopsis anchiops, Mannopyge halli, and Trypaulites erinus.
(Pictured above: an apparent large, albeit incomplete, gastropod steinkern)
I must have picked over these rocks in the pit, hill, and surrounding area about 30-40 times this year - if only because it is conveniently just beyond my backyard. Rocks from the Dundee, Amherstburg, and Bois Blanc formations abound. Of course, there are hardly any larger rocks left to split so perhaps a good winter will weather out some promising rock for next season. I do secretly wish that more rock gets imported, but it has been a few years now.
(Pictured above: a few brachs, including some lovely vermillion-coloured Leptaena - a brachiopod that is fairly abundant in this area).
I have a soft spot for this location ever since I found some coral and a spirifer back in 2013. I had been walking the trails back there since 2010 or so every autumn, but finding those fossils rekindled a childhood passion of mine, and at a time when things were particularly very challenging in my life.
(Pictured above: more Leptaena)
How far I've come since, and as I've changed and grown, so too has the site itself. Every year it takes on a radically new appearance, with new exposures, new lines of undergrowth. When I started picking things over here, all I had was a rusty old nail hammer and a wood chisel. Today I have my arsenal of precision rock hammers, sledges, and cold chisels. With better tools, better knowledge, and a better eye, better specimens have been the happy result.
(Pictured above: trilobite pieces (cephalon fragment, pygidium fragments, thoracic fragment).
I've collected at locations that have far more diversity, fossil abundance, and more interesting specimens, but this collecting location is special to me. It is the place where it all began (or at least picked up where I left off in childhood). It is the place that provided me with respite during very bad times. A place of solace and surprise, situated where I am the happiest: in nature, among the rocks and trees.
This site has been exceedingly kind to me this year, and even if next year's finds may be minimal, it has been generous enough already. And although I may only come back with something of interest to me once out of every 4 or even 10 visits, it is still a place where I never feel the time spent was time wasted. And just when I least expect it, that there is really nothing to be found on a visit, it just takes one rock split to transform a casual visit into a trip to remember.
So today I decided to spend part of the morning at that site near my house, the infamous "riprap hill" and associated pit. I've long suspected most of the rocks I split there were trucked in, and have confirmation of that due to the three different kinds of trilobite I've pulled from it (two in the last four months - Anchiopsis anchiops and Mannopgye halli).
I had been finding examples of rock from the Hamilton Group, Dundee Formation, Bois Blanc Formation, and the Amherstberg Formation. A good and wide range of Devonian age rocks.
As can be seen above, the usual assortment of brachiopods and a gastropod. My expectations were low as I'm running out of rocks to break after four years of scouring the place.
Ok, but what about this? I get the line by Morpheus in the Matrix in my head saying "what if I told you everything you knew was a lie?" So at first I was in disbelief: this must be a shell impression, not the impression of a trilobite pleura. But I've seen this before. In the Ordovician. Yes, it is a fragment of a Pseudogygites. The nearest Ordovican outcrop is 300 km away.
If I needed further proof, I flipped over this piece of shale and saw a fossil barely bigger than the head of a pin. Putting it under the microscope, it is indeed the cranidium of a Triarthrus.
Oookay, then. Confirmed: dumped rocks that span over 100 million years. From a field perspective, this is going to make things much tougher in terms of certainty over finds, but I suppose it means a veritable potential bonanza of finds spanning a much broader range of geologic history.
I spent the entire morning on Saturday at the hill & pit just beyond my backyard. My expectations were fairly low given how much I had picked the place clean over the years, so it was my goal instead to take pictures and record some of the fossil fauna there for posterity. How plans can get upended - sometimes in unforeseen yet lovely ways.
This picture is not exciting, nor was it meant to be! I began on the southwest portion of the hill (which is now pretty weedy with burdocks and spiky plants, by the way!). I had not spent a lot of time in that lower quadrant as I always seemed pulled to the upper southwest and southeast areas. Pictured here is a typical brachiopod assemblage - some spirifers, an atrypa-type, a Leptaena, and other assorted kinds. As I said, the purpose was to photo-document the typical stuff of the Bois Blanc Formation.
Another very typical assemblage from another distinct layer of the Bois Blanc. This tiny brachiopods can be quite numerous (I forget their name at the moment). So numerous, in fact, that some of the rocks bearing them actually are more shells than matrix, and just crumble. There are several examples of this type of assemblage in the area where the brachiopods are stained a kind of vermillion.
A similar assemblage to the first picture - some atrypas, a leptaena, and a large ?Strophodonta. Bored yet?
Performed a brief scan of the upper south quadrants and assembled a few of the specimens I had set aside from previous visits. If you zoom in for detail, you'll see, left to right, a rather chunky brach assemblage (name escapes me at the moment!), a lingulid pelecypod, a horn coral, and a typical (for particular layers in the Bois Blanc as a signature feature) cherty rock with a few corals showing cross-section. By this time, I had enough of the hill and was ready to give the adjoining pit another try.
Oh, but wait - I was distracted by a rock I had split and left behind some weeks ago. I decided to break it down to pluck two bryozoan specimens. The first pictured above is a typical fenestellate bryozoan. The next is a bit more peculiar...
Now what the heck is this? I made inquiries on The Fossil Forum, but at best we might describe it as Sulcoretepora. As described by a single specimen in the Amherstburg Formation by J.A. Fagerstrom:
"This specimen is a short bifoliate stem with three rows of apertures on each flattened side and none on the edges. Slightly raised longitudinal ridges separate adjacent rows of apertures. Apparently no mesopores are present between apertures but they may have been destroyed by recrystallization" (17).
Fagerstrom, J.A. (1961). The fauna of the Middle Devonian Formosa Reef Limestone of southwestern Ontario. Journal of Paleontology 35(1):1-48.
There are some interesting branching, radiating patterns in this one, with two zooecial apertures near the upper left and upper right corner (the dimply stuff). Colony form here is likely remnant of bryozoan encrusting substrate (with thanks for our experts on the forum). But why are we even talking about Amherstburg Formation? Let's keep this flagged for the time being.
I was not expecting to find any trilo-butts, but I managed to find about six. So now I am in the pit and can confirm that it contains Bois Blanc formation rocks. I dug this rock out of the wall of the pit, and pictured above is the pygidium of the dalmanitid trilobite Anchiopsis anchiops (which only appears in the Bois Blanc), but missing its full trademark pygidial spike.
Some in situ photos from the pit as I work the same rock. The top picture shows some typical assemblages, while the two lower pictures are closeups of the most frequent brachiopods.
Trilobite impressions (Anchiopsis anchiops). I took the positives home.
After I patrolled the rest of the pit and did not find much more to my liking, it was time to go home and take stock of the finds. Pictured above is a gastropod steinkern (the inner whorl occurs on the reverse side). Beneath that is a nicely inflated clam, and on the right is another spike-deprived Anchiopsis anchiops.
This specimen, found on the hill, is the real "meat" of this post. This is not a trilobite that appears in the Bois Blanc, but solely in the Amherstburg formation. The Amherstberg is a younger formation, contiguous with the Bois Blanc if there is no Sylvania formation intervening. Note the nodules on the fringe of the pygidium.
Consulting Ludvigsen's 1979 text, Fossils of Ontario. Part 1: The Trilobites, there is a specimen reported that looks nearly identical to this one, but it is simply called Dechenella halli. The name was updated by Ludvigsen in 1986 and recognized as a new genus: Mannopyge halli.
Here is a plate from the Ludvigsen 1986 text on the left, compared to my find on the right:
Quite exciting, as this makes the 19th species of trilobite in my expanding collection (I've more than doubled it since March of this year alone). Let's learn more about it:
"A warburgelline with pear-shaped glabella, deep sigmoid 1s furrow, narrow (tr.) and faint 2s and 3s furrows; no preglabellar field, tropidium, or tropidial ridges. Large eyes located anterior of cephalic midlength; genal spines short. Semicircular pygidium iacks a flat border,-axis with 9 - 10 node-bearing rings, eight faint pleural furrows and incised interpleural furrows, each pygidial rib terminates abaxially as a rounded node isolated by moderately deep paradoublural furrow. [...] No other warburgelline has a semicircular pygidium, and none possesses a conspicuous row of fringing nodes such as that of Mannopyge. The pygidial pleural ribs of M. halli, however, are of the flat-topped warburgelline-type (Owens 1973, Fig. 2), and there is no reason to doubt that Mannopyge is a late member of the subfamily Warburgellinae." (Ludvigsen 1986, 683).
Ludvigsen, Rolf (1986). Reef trilobites from the Formosa Limestone (Lower Devonian) of southern Ontario. Canadian Journal of Earth Sciences (24): 676-88.
Two remarks: First, this tells me that there are some Amherstberg formation rocks in the mix at this site. Second, trilobites in the Formosa reef limestone are not particularly common, dominated as it is by coral and stromatoporoids. Of the uncommonly found trilobites in that limestone, it is mostly dominated by Crassiproetus, followed by frequency occurrence Mannopyge halli, followed - in descending order of frequency - by Mystrocephla, Acanthopyge, and Harpidella.
I'll leave off today with a few more pictures, mostly to underscore that my picture-taking ability has seen a little boost in quality on account of having acquired the third-party app, Camera+, so that I can take proper macros. Using an iPad to take closeup images can be a bit unsatisfactory, but the app I purchased allows me to get in much closer and increase the resolution (which is probably why those of you with slower bandwidth are cursing me right now). As a test, pictured above are two sides of the same piece of crinoidal limestone found at Penn Dixie.
And this is a closeup of a coral piece from Arkona. I'm pleased with the detail.
Ok, enough from me until next weekend, when I'll be headed to a quarry east of Lake Simcoe for some serious Ordovician collecting. Until then, thanks for reading!
Now that the course I was teaching is done, and the heavy rains are behind us, thoughts turn back to the hunt. The heavy rain system that lashed a lot of Ontario and western Quebec left a great deal of flooding. Fortunately, not as much here, but the rivers and lakes had been dangerously high, making any collecting near them too dangerous.
But as it is the long weekend, Deb and I got out to Arkona for a five hour hunt. Overall, not a hunt that bagged the best specimens, but we weren't skunked either.
This is the north bank. The photo does not show the proper scale for the bench I worked out. It was already started by someone else, but I was able to lever out two enormous slabs weighing maybe 300-400lbs each. The slabs were partially covered by overburden, so I underestimated their size until I started seeing a crack. But with a lot of grunting and levering with the pry bar, I freed them and rolled them down the hill to be worked on.
Anyone who has worked the Widder shale before knows all too well that one has to go almost quite literally through tons of it to find a full Greenops. Instead, hundreds of moulted bits are quite plentiful.
There are layers in the Widder almost entirely dominate by spirifer brachiopods, but they are trilobite-poor.
Patience and a lot of hammer blows / rock busting can be rewarded. I was able to call first blood on a likely near-complete Greenops widderensis after a few hours working the slabs. Sadly, this one is tucked in the matrix (but can be worked out) and is missing a chunk of its right cephalon.
But it seemed a pretty good day for nautiloids. Pictured above are three Michelinoceras sp.
This one may be a bit more of a challenge to make out, but if you look closely you can see the spiral shape, with a bit of the texture showing in the upper left (the brassy, pyritized stuff). This would be a Goniatites, and a fairly large one for this strata.
And last up: Deb found her complete Greenops (also tucked in matrix, but in better shape than the one I found). On the right is another semi-inflated pyritized Michelinoceras that I'll have to chip out of the rock.
Pictured above is a before and after picture of the nautiloid I found, prepped with a Dremel. Came out fairly well, but this is as far as I dare to take it using an engraver. One day, air scribes and compressors will be needed!
So that's about the long and short of the five hour Arkona trip. Below are some other odds and sods:
Paid a visit to my local rock shop run by two very nice folks. I picked up these two Flexicalymene ouzregui (Ordovician) from Morocco's Anti-Atlas mountains.
A busy brach hash plate from the Bois Blanc Fm fill out in my back nine.
Nice big brach + impression from the same area.
And lastly, another example of Anchiopsis anchiops - pygidium missing its pygidial spike. Lower right I suspect is just a worn and partially buried Eldredgeops rana. Below is a close-up of the Anchiops with some diagrammatic details provided by our Fossil Forum's resident trilobite expert, Scott. "Anchee," as I will call it, is a dalmanitid trilobite, and the way to tell it is by such an incomplete specimen would be the incised axial rings, shown by the arrows in the re-cropped photo below:
I actually didn't anticipate posting again until after the upcoming dig at Penn Dixie, but two consecutive days of collecting at my riprap hill nearby has brought some excitement into the collection.
For some many years of collecting from this place, I knew a lot of that material was shipped in. My assumption was that it was more locally sourced (and thus mostly Dundee Formation). Many of the fossils I was pulling from there are reported as part of the Formation. Until I found one that wasn't. But also peculiar were the fossils I was NOT finding that are typical of the Dundee. Not even typical of the Hamilton Group (Arkona, Widder, etc.). I guess I was blinded by what I assumed to be true as opposed to facing the cold, objective truth as evidenced by the biota.
Yesterday I found this:
And a closer view:
So, fairly eroded away, leaving only a cast/mold of a part of the cephalon of this trilobite. But it is a whopper. I don't really find Devonian trilobites approaching this size (Ordovician ones, yes). So I posted it on the fossil forum, and our resident trilobite expert Scott weighed in and said it was either Trypaulites calypso or Coronura aspectans, both of which are recorded in the Dundee Formation. There isn't a lot of diagnostic details to go on, but you can make out the distinctive occipital ring and the deep furrow on the lower left of the cephalon. So, we know it could be one of these two dalmanatid trilobites, right? Hold on...
I spent another four hours today carefully taking on any rock on the hill, splitting it, and seeing if anything interesting might come up. As I've pulled Basidechenella from there in the past, I was hoping for more than just another pygidium. There was this one greyish, round rock about the size of a softball lying there. I wasn't going to bother with it as I thought it would just be another blank, or just one of those dense balls of largely erosion-resistant rocks where you have to bring out the big guns to split it and find only a tiny smattering of brachiopods. But I was already sitting in the gully breaking rocks, not in a hurry to get back up, so I thought, "why not while I'm here?" So glad I did, because this was the rock that became the key for determining the origin of many of the rocks on this hill - and thus explains the biota.
Without double-checking, I thought, "ok, another Trypaulites specimen. That's pretty lucky to find two in less than 24 hours." I assumed from my patchy memory of looking at a Trypaulites in the Ludvigsen volume. I really should have looked more closely to confirm that assumption. I was still tickled pink to find another specimen. But when I posted it, Scott chimed in again by saying it was NOT a Trypaulites. It was instead a Anchiopsis anchiops, and those only occur in the Bois Blanc Formation.
The only significant outcrops of Bois Blanc are hundreds of kilometres away, in the Niagara escarpment. So what the heck was it doing here in London, Ontario? There is no doubt on the ID of this one. I checked the literature and, Scott was bang on as usual. Scott then revised his earlier ID on the big cephalon above and said it was also Anchiopsis, but missing the distinctive occipital spine. Here are the images Scott presented for comparison with what I found:
So I went back and took a longer look at the several finds I've made in this location over the past four years. I compared those to what was listed in the Bois Blanc, and there they all were. What didn't tip me off is that there is a great deal of overlap of species between the Bois Blanc, Dundee, and other formations in the Devonian. For example, the trilobites Eldredgeops rana and Basidechenella sp. appear in both formations. I had reasonably assumed that the materials delivered and dumped to make this hill would be more locally sourced, as that would seem more economical. And thus I stuck with my first assumption that everything I pulled out of the hill was likely Dundee Formation or thereabouts. But the presence of the Anchiopsis throws all of that out, as it ONLY appears in the Bois Blanc. So, in sum, I am collecting from the Niagara escarpment pretty much in my backyard. The stratigraphy is as follows in descending order of age:
The Bois Blanc is the second oldest Devonian strata, underlain by the Oriskany. According to Armstrong and Dodge (2007):
"The Oriskany Formation is disconformably overlain by the grey to brown, very cherty, fossiliferous, argillaceous limestones and dolostones of the Bois Blanc Formation (Uyeno et al. 1982). Thin beds of glauconitic quartz sandstone that occur near the base of the Bois Blanc are assigned to the Springvale Member (this member is not shown on OGS maps). The Bois Blanc Formation outcrops and subcrops in a narrow belt from Fort Erie on the Niagara River to MacGregor Point on Lake Huron. North of Norfolk County outcrops of this unit are sparse."
According to Ludvigsen (1979), there are five major genera of trilobites in the Bois Blanc: Phacops [Eldredgeops] rana, Basidechenella sp, Crassiproetus sp, Anchiopsis anchiops, and Terataspis grandis. I have so far collected three of the five.
I could dare to dream in finding, say, one of the most famous of all trilobites - a monster at over 50 cm or more, for which only fragments have been collected, Terataspis grandis:
I'm not saying I will find one, only that it is now possible. The probability of finding one is entirely different story.
So I've now had to reassess my assumptions that have been engrained for years, and I am delighted to be wrong and to welcome yet another new species into my collection - quite a few with the season just beginning. I'll sign off with a pic of some other finds of the day:
As temperatures slide into spring, the semester drawing to a close, I am back out in the field ending my cabin fever. Pictured here are a few finds from one of my nearby honey holes, some of which I've found in the past but did not post pictures of.
Pictured above and in the next two pictures, are pieces of a coral. It has been identified as likely Triassic or Jurassic in origin. How it came to be in a largely Devonian area is a mystery to me!
Here is a bigger chunk of the same coral. The shell type at the top is likely oyster.
This one was found along the Thames River at the university. Initially I thought this might be a transversely placed Megastrophia sp. brachiopod showing only the hinge, but it just doesn't seem to fit. Could it be a worm tube? Seems a bit too straight to be one. A mystery!
Above: a picture of the "riprap hill". Below: typical littoral.
Simple brach hash.
Nothing wow here: a chunk of tabulate coral, two brachs, a worn piece of Aulopora, and a general marine hash.
Worn gastropods. Hormotoma type on the left.
Leptaena sp. brachiopod, red on brown-grey matrix.
Hash plate with trilobite pygidia.
Fragments of two new species of trilobite for me. On the left is a piece of pygidium from Trypaulites calypso, found along the Thames River. According to Ludvigsen (1979), no specimen of this species has been collected in Ontario, although the equivalent strata elsewhere would suggest it should appear. This * might * be the first confirmed find of this species in the Dundee Formation in London (very exciting!). On the right is a partial cephalon impression of Basidechenella sp. to go along with a few of the pygidia that I sometimes pull from this area.
This now brings my trilobite tally to 10: Eldredgeops rana, Greenops widderensis, Greenops boothi, Basidechenella sp., Trypaulites calypso, Flexicalymene ouzregui, Pseudogygites latimarginatus, Triarthrus eatoni, Proetus sp.
This year, if time and travel permit, I hope to add a few more - particularly from the Ordovician. Stay tuned, for I'm returning to Penn Dixie this week for a multi-day dig. For now, here is a pic of me and the missus from last October that the PD folks put up on their website:
Keeping closer to home, I've managed to pull some interesting if not typical specimens from the Dundee Formation along the Thames River. I even found a pitifully small trilobite pygidium (really not worth showing). The more visually interesting specimens happen to be coral, a few brachiopods, and bivalves. Unless otherwise indicated, these are all from the Dundee Formation, of the Devonian age, Eifelian stage. Not shown in these images were the plentiful and more robustly ribbed Brevispirifer lucasensis. So, let's show rather than tell:
A fairly well-preserved chunk of colonial coral (?Favosites sp.). I don't usually go in for coral, but this one was a must-have.
Another busy hash-plate containing some rugose corals (?Zaphrentis sp.), a brachiopod (Rhipodomella sp.) and a bryozoan (Fenestella sp.).
Now that I'm back on campus teaching again, I took a few more pictures of the fossils in the wall of the Visual Arts Centre. The picture above already appears in my pre-blog entry, and I had misidentified it as a coral rather than a sponge (although it is nicknamed a "sunflower coral" due to its resemblance to a sunflower). It is a Fisherites ?occidentalis (formerly Receptaculites occidentalis, Blainville 1830, genus changed in 1979, Finney & Nitecki). The building's composition is Tyndall Stone (trademark of Gillis Quarries), Ordovician in age (Maysvillian stage), in the Selkirk Member of the Red River Formation quarried in Manitoba - incidentally the same material used in the Parliament Building. It is a dolomitic limestone mottled by many corals and thalassinoides.
Another image of the same limestone sporting two fairly large nautiloids side by side, siphuncle showing in the specimen on the right. There are also several large gastropods if you take the time to scan the exterior of the building.
And here is one such gastropod, Hormotoma sp.
The mottling of this limestone was a bit of a puzzle for some while. The mottling is something of enormous interest for the ichnologist (study of fossil burrows and traces). Here are some helpful papers on the subject:
Kendall, A.C., 1977. Origin of dolomite mottling in Ordovician limestones from Saskatchewan and Manitoba. Bulletin of Canadian Petroleum Geology, v. 25, p. 480-504.
Myrow, P.M., 1995. Thalassinoides and the enigma of early Paleozoic open-framework burrow systems. Palaios, v. 10, p. 58-74. (PDF)
Sheehan, P.M. and Schiefelbein, D.R.J., 1984. The trace fossil Thalassinoides from the Upper Ordovician of the eastern Great Basin: deep burrowing in the early Paleozoic. Journal of Paleontology, v. 58, p. 440-447.
And that is all from me for now. I'll be heading back to the Penn Dixie site in early October, now as a new and proud member of the Hamburg Natural History Society, for a two day dig.