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
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!
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.