Season 2, Episode 3: A Midsummer Day's Dream
As autumn stealthily approaches, and I gear up for the new year by preparing my course lectures, it is hard to resist the call of the fossils that are just a five minute walk away from my house. In this episode, I hit one of my favourite nearby fossil collecting sites and come away with a wonderful surprise.
This odd piece resembling a tricorne hat is a brachiopod, and specifically a paraspirifer (Paraspirifer acuminatus). Unlike the other spirifers I've been pulling out of this site, this one is characterized by being fairly bulky. So, the burning question on everyone's mind (well, maybe not...) is how does one tell the difference between a brachiopod and a bivalve?
As the diagram above indicates, it is all about planes and symmetry. A brachiopod is identical on both sides of its face on the dorsal or ventral valves, BUT that the dorsal and ventral valves are not symmetrical. This means brachiopods are inequivalved, whereas bivalves (think here of clams) are equivalved as they are symmetrical from the side view.
The paraspirifer I am holding does qualify as a brachiopod. Not pictured is a bit of pyritization of the foramen - or, the valve hinge. Its state of preservation is not ideal, for the ridges are slightly worn from erosion. Still, it is a fairly large piece compared to the spirifers in this particular area. |
Over the last two-three months, my frequent visits to the pit I collect from near my house has yielded up a lot of spirifers, and not all of them are pictured here. It's amazing how quickly one can accumulate them. There are 99 pictured above, and my goal is to mount 100 of the very best and complete specimens in a 10 x 10 compartmentalized box. One option would be to find the compartment cases used by typesetters, place a sheet of glass over it, and make a shadow box.
Here I am holding what I assume to be another paraspirifer very well articulated.
Here we have an interesting assortment of odds and sods. We mostly have bivalves here, but what I am holding between my fingers is a pyrite nodule I pulled from ferrous shale. The shale itself was entirely devoid of fossils, but was very rich in pyrite. This is just one of the nodules I opened, and I have two others that I have yet to open.
Pictured next to my well-used e-cigarette is a gastropod; more specifically, Euomphalus laxus (thanks to Bob from the Fossil Forum for the pinpoint ID!). I admit to being temporarily excited that it could have been a cephalopod, but I suppose I can be satisfied in adding an interesting gastropod to the collection. |
It was fairly late in the evening, about an hour before sunset, and I decided to roll in my usual evening walk with a short visit to the pit I frequent often, not expecting to find anything more than the usual assortment of spirifers. Living as I do in the seemingly endless stretch of the Dundee Formation with its monotonous biota of corals and brachs, I began exploring a chunk of calcareous grey shale-limestone transition, and out popped a trilobite. I have been revisiting this site for months and NEVER encountered a trilo before, and certainly never expected to find one. Yet, there it was!
As the sun was setting, I had to work quickly, and just a few minutes later I found another, albeit smaller, specimen. This is an Eldgregeops rana, possibly E. rana milleri, showing just the pygidium and thorax, measuring about 1 3/4 inches (with the cephalon, it would have been a little over 2 inches).
As the sun was setting, I had to work quickly, and just a few minutes later I found another, albeit smaller, specimen. This is an Eldgregeops rana, possibly E. rana milleri, showing just the pygidium and thorax, measuring about 1 3/4 inches (with the cephalon, it would have been a little over 2 inches).
This picture is provided to show a sense of scale of the new trilobite acquisitions.
Although I have read that it is possible to find trilobites in the Dundee Formation according to the lithofacial analyses, the probabilities have been remarkably low. Moreover, the lack of exposed stone does limit one's opportunities. Here in London, much of the fossil record remains buried under a very deep layer of sand, overburden, and glacial till.
I am, however, uncertain if the stones at this site are naturally occurring as a result of digging, or if there has been some importation involved. I am leaning toward the first explanation, and it would appear there is at least some evidence of E. rana milleri present in the silica-shales of this formation.
2015 season now available
Although I have read that it is possible to find trilobites in the Dundee Formation according to the lithofacial analyses, the probabilities have been remarkably low. Moreover, the lack of exposed stone does limit one's opportunities. Here in London, much of the fossil record remains buried under a very deep layer of sand, overburden, and glacial till.
I am, however, uncertain if the stones at this site are naturally occurring as a result of digging, or if there has been some importation involved. I am leaning toward the first explanation, and it would appear there is at least some evidence of E. rana milleri present in the silica-shales of this formation.
2015 season now available