Friday, August 30, 2013

Strophodonta crassa from Michigan

This fossil is a Strophodonta brachiopod from the Potter's Farm formation near Alpena, Michigan. I've looked through the book "Strata and Megafossils of the Middle Devonian Silica Formation" and I believe this can be classified as Strophodonta crassa. The radial ribs are much coarser compared to the typical Strophodonta demissa and the shell is thinner.

Pedicle valve
Brachial valve

Here is another specimen that is just the pedicle valve

The Potters Farm formation is part of the Traverse Group of rocks in Michigan. They are dated to the upper Givetian stage of the middle Devonian. I received both of these specimens from a member of the Fossil Forum but I don't remember his member name.

Some specimens of Strophodonta crassa are pictured on the Friends of the University of Michigan Museum of Paleontology's web site Here.

Wednesday, August 28, 2013

Emanuella praeumbona from the Centerfield

I found this brachiopod fossil in the Centerfield formation of New York. It looks superficially like an Ambocoelia umbonata except that the brachial valve is more convex and the sulcus is much less pronounced. Also the overall shape of the shell is slightly "fatter" than Ambocoelia. It is for these reasons that I am labeling it Emanuella praeumbona.

Brachial valve
Pedicle valve

The Centerfield member is a part of the Ludlowville formation and is middle Devonian (Givetian stage) in age. Compare this to Ambocoelia umbonata fossils that I've found in the Hungry Hollow member of the Widder Formation (Ontario, Canada) and the Needmore Shale (Pennsylvania)

Monday, August 26, 2013

Chesapecten nefrens pelecypod from Maryland

Another group of pictures from my folder clean up feature this Chesapecten nefrens pelecypod from the Calvert formation of Maryland. I collected this 25 years ago while on a trip to Calvert Cliffs in Maryland. It was found in the Choptank formation while staying at Matoaka Cottages.

Left valve

Right valve
Right profile

Interior of both valves. The white paint and ink lettering were a short lived attempt by my younger self to catalog my fossil collection at the time. In this case the "CC" stood for Calvert Cliffs and the number indicates that this was the first numbered specimen (but not necessarily the first specimen I found).

The Choptank formation dates to the Miocene epoch (Langhian to Serravallian stages) of the Neogene period.

Saturday, August 24, 2013

Some trilobites from the Wheeler Shale

Continuing my clean out of a folder with some older pictures, here are some Trilobites from the Wheeler Shale near Delta, Utah.

These first few specimens are Agnostid type trilobites which are fairly common in some layers of the Wheeler Shale. I believe these are called Peronopsis interstrictus. I collected them about six years ago from an outcrop that was teeming with the little guys.

Next up is a large (2" long) Elrathia kingi that popped off the shale matrix. This is somewhat common, especially if the shale is weathered a little bit. The trilobites are preserved with Calcite which is a bit tougher than the soft, layered shales they are contained in. I purchased this specimen and the next one from West Desert Rock Art, a small rock and fossil shop in the town of Delta, Utah.

Lastly we have an Asaphiscus wheeleri.

The three trilobite species shown above are the most common fossils in the Wheeler Shale. There are dozens of other species that can be found but some are more rare, or restricted to certain layers within the shale. The Wheeler Shale dates to the middle Cambrian. Here is a great page from concerning the Wheeler Shale.

The fossils are so abundant, and exposures so easy to find/mine that there are a couple of fee quarries that you can try out while in Delta. One, that I have visited, is U-Dig Fossils. If you follow that link to their web site you will see that they now offer a service where they will ship you some of the fossiliferous shale that you can split at home. A fine alternative if you can't make it out there yourself.

Thursday, August 22, 2013

Fossil Ginkgo leaves from British Colombia

I'm cleaning out a folder of pictures this week. Here are some photos I took a few years ago of a few Ginkgo fossils from the Eocene aged Tranquille shale in British Columbia, Canada.

Ginkgo dissecta

Ginkgo dissecta

Gingko adiantoides

Tuesday, August 20, 2013

Eurypterids from the Ukraine

I'm cleaning out a folder of pictures this week. Below are pictures of three Eurypterid fossils from the Ukraine. They are likely Balteurypterus tetragonopthalmus as that seems to be the most common species that I see available on in the Internet. They come from near the River Smotrych in the Kamianets-Podilskyi region of Khmelnytskyi Oblast, Ukraine. The age is late Siilurian (Pridoli stage).

This is the most complete specimen and the smallest. It's just a spall off of a larger piece of Dolostone.

This is what it looks like when put back into place.

The next fossil is a bit larger but more incomplete.

The last specimen is very fragmented and has been patched back together from several smaller pieces.

The rock in which these fossils are preserved is very similar to that which is found in New York and Ontario that are part of the Bertie group. A yellow-tan, fine grained dolostone which is interpreted to represent sabka (salt flat) type environments where a shallow lagoon is host to hyper-saline water due to higher evaporation rates than can be refreshed by the ocean during high tides. These kind of environments are found today in the Persian Gulf region. A theory posits that the Eurypterids would migrate to the lagoon to molt since the hyper-saline water would prevent predators from following and preying on the arthropods while their new exoskeletons hardened.

Sunday, August 18, 2013

Fossils from the Alden pyrite layer of the Ledyard shale

I had the chance to sample the Alden Pyrite bed, within the Ledyard shale of the Ludlowville formation, this past May in a stream bank near the town of Alden, NY. The Alden Pyrite bed is so named because it is a layer of shale that has a high proportion of the fossils replaced by pyrite and often encased within nodules of the same mineral. Karl Wilson has a nice page of what he's found in the Alden pyrite beds at his website. Here is some of what I found:

A partial Mucrospirifer

This is a pelecypod that is partially surrounded by pyrite as well as having the shell replaced. It's likely a Nuculites triqueter or Nuculoidea corbuliformis.

A Gastropod which could be of the Bembexia genus.

This was the prize of the trip for me. A nice large Tornoceras uniangulare fossil. This is a nice comparison piece those that I've found at Arkona.

Another brachiopod that was relatively abundant was Ambocoelia umbonata

Another small Pelecypod

The day I was at the creek there was another gentleman who was actively mining the layer. He found two Spyroceras fossils, one of which had a large nodule of pyrite at one end. The Ludlowville formation is middle Devonian in age (Givetian stage).