By far the biggest attraction at the St. Mary's Cement quarry is the possibility of finding the trilobite Pseudogygites latimarginatus. In the Coburg formation they can get pretty large and make for a nice prize when found. They are also found in the overlying Whitby formation, but I will show you those fossils in another post. P. latimarginatus oval shaped with a large, flat, shield like pygidium that has strong ornamentation on it. It has a strong axial lobe with radiating ribs extending to the margin. I've not found a full specimen in the Coburg formation yet so most of what I have are pygidiums.
This is best preserved specimen that I've found.
I kept this sample as an indicator of the size they could attain. If the fossil had been complete it would have been 6" across!
On one trip to the quarry, a friend found a large lab of rock with nine+ examples of P. latimarginatus on it. Most were in great shape but a few were lesser specimens. He cut them out of the rock with a saw as the slab was far too large to haul away. I was lucky to receive one of the lesser pieces that I can use as an example and to inspire me to keep looking.
The Coburg formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
These fossils were collected from the St. Mary's Limestone Quarry in Bowmanville, Ontario. I used William Hessin's book "South Central Ontario Fossils", 2009, Self Published, pg. 200 to help identify them.
No comments:
Post a Comment