Pristeroceras timidum cephalopod from the Bertie Formation

This is one of the oddest fossils I've found in the Bertie limestone, it's a cephalopod called Pristeroceras timidum. It appears to have possessed a very thin shell or maybe one that was not permineralized like other cephalopods.  Pristeroceras timidum is considered a breviconic type of Cephalopod in that it did not form a long conical shell but instead opted for a subovoid shape. In the Bertie formation the shell is often very compressed and so fossils do not present many details.

This is the specimen as found in the field. Note the light colored pattern on the darker colored shell.

The other side of the enclosing limestone broke into a number of smaller pieces that I've glued back together.

The cast of the fossil popped off the matrix and allows me to see both side. Here is the impression of the side that was hidden from view in the first picture.

A closer view of the top limestone later

Here is the body fossil itself. The pattern that is evident on the shell is the opening where the animals head and tentacles emerged.

The back side of the fossil shows a wrinkled pattern due to the compression.

I got some of the info for this post, including the image below, from the following paper:
"A Restudy of the Silurian Nautiloid Genus Pristeroceras Ruedemann"by Walter C. Sweet and Willard P. Leutze,Journal of Paleontology, Vol. 30, No. 5 (Sep., 1956), pp. 1159-1164

Eurypterus lacustris from the Bertie formation

This past fall I finally found some Eurypterid fossils while visiting the Ridgemont Quarry near Stevensville, Ontario, Canada. It was my fourth or fifth trip to the quarry and previously I'd only found isolated parts of the animal. None were 100% complete but all were more than I had ever found. At the quarry the fossils are found by splitting thin bedded dolostone. The beds formed in a lagoon like habitat that was shallow and low in oxygen. Because the rock is dolomite this can be taken as evidence that the paleoenvironment was very warm with rapid evaporation. This is further reinforced by layers that have mud cracks preserved. Most of the fossils of Eurypterids that are found are molts of their exoskeleton. Depending on how quickly they became buried they would often break apart into smaller individual segments and be scattered by the currents. Thus to find any specimens of whole or nearly whole bodies is rare.

Here is the pit I was working

My finds as I had them set aside before I wrapped them up

Specimen #1 is a positive and negative of the same fossil that is just the front half of the animal. Note that the lower plate is two smaller pieces that I glued back together. This is not uncommon at the site as the dolostone is very fragmented in places with cracks from previous blasting (it is an active quarry after all).

Specimen #2 is mostly intact but has many bits and pieces scattered about. The exoskeleton may have started to disintegrate just before it was buired or the pieces are from a different exoskeleton.

Specimen #3 is the most intact with nearly the entire Teslon (the spiny tail bit) and one of the swimming arms. I have no idea what happened to the upper half of the other side. I must have lost it among the rock debris during excavation and was not able to find it.

Inocaulis fossil from the Bertie formation of Canada

One of the odd fossils that I've found at the Ridgemont Quarry near Fort Erie, Ontario, Canada are these positive a negative specimens of an enigmatic fossil called Inocaulis plumosa. It's been something of a mystery for a number of years and has been thought to be an algae or possibly a graptolite. Well there is a new paper coming out (in Alcheringa, the Journal of the Association of Australasian Palaeontologists) that states, based on new fossils from China, that it most certainly is a graptolite (possibly a dendroid or tuboid type).

I photographed the fossils wet to better show detail.

 

Graptolites were colonial animals that lived similar lives to a coral or bryozoan in that they filtered the water for food. Most were free floating but some did attach to the substrate. They are more closely related to vertebrates than invertebrates. The fossil does show some "hairy" extensions around the periphery of the body. This is only part of what was likely a larger group of animals. The specimen was found in the Bertie formation which is Silurian (Pridoli stage) in age.

Cooksonia plant fossils from the Bertie formation of Canada

Cooksonia is one of the first recognized vascular plants. That means it had a system that allowed water and nutrients to be distributed internally. This is an important step for a plant if you are going to exist outside of a watery environment. The specimens below are individual pieces of what could be C. hemisphaerica likely before they fully produced their sporangia.

Specimen #1

Specimen #2

Specimen #3

All three specimens came from the Bertie formation (upper Silurian, Pridoli stage) in Ridgemont quarry, Fort Erie, Ontario, Canada.

Fossil Algae from the Bertie formation in Canada.

I'm a little surprised that I hadn't posted anything regarding some plant fossils I found last fall in Canada. These next few posts should rectify that starting with some humble Algae. The carbon coating on dolostone below is thought to be a fossil algae and was found in the Bertie formation at Ridgemont Quarry, Fort Erie, Canada. The Bertie formation is better known for it's Euryptid fauna but plant material is actually more rare.

This was collected last fall from the Ridgemont Quarry which is kind enough to allow collectors access to their property to prospect for fossils. The Bertie formation is late Silurian (Pridoli stage) in age and has been interpreted as a shallow lagoonal deposit.