Sunday, June 30, 2013

Pleurodictyum from the Kashong shale of New York

Pleurodictyum is a favorite coral of mine and recently I found a couple of specimens at a site that exposes the Kashong shale member of the Moscow formation in New York. Both are smaller than most that I find but the details are well preserved.

Specimen #1 - This one was found by my friend Mikey who gave it to me since I had not found too many of my own yet.

I need to clean the shale off the bottom of this a little more to see if I can find an impression of what the coral settled on when it started to grow.

Specimen #2 - When I first found this specimen I thought it might be Alveolites as it was growing on the side of a Crinoid stem section. After cleaning I can see that it clearly is a Pleurodictyum americanum.

Below you can see the flat base of the Pleurodictyum. If this were an Alveolites then the coral would wrap around the Crinoid stem and there would be evidence of constricted growth of the stem itself. There is a bryozoan that had previously grown on the stem so I think this was a case of the Pleurodictyum colonizing a piece of crinoid stem that was partially buried in the mud. The first poylp settled on a hard surface (the crinoid stem) and started growing before being later smothered by shifting currents or a storm flipping it over.

The Kashong shale is a member of the Moscow formation within the Hamilton Group of New York. It is dated to the middle Devonian (Givetian stage).

Friday, June 28, 2013

Spinatrypa spinosa from the Windom shale of New York

I've profiled Spinatypra from the Windom shale before but recently I found some specimens that have many more of the spines that decorated the shells intact. I was exploring a hillside exposure of the shale that my friend Mikey had led me to and I came across a total of three specimens. The shells had been compressed flat but amazingly there were spines still in place.

Specimen #1 

Specimen #2

Specimen #3

These are really neat specimens that help to better understand what the animal looked like. Most specimens that are found do not have the spines since they break off either prior to burial or upon extraction (mechanical or via weathering) from the rock. It's interesting that these specimens are smaller than those I've found at the Penn Dixie site. The exposure of Windom shale is also much thicker at this hillside site than what is found at Penn Dixie and 18 mile creek. The Windom shale is a member of the Moscow formation which is dated to the Givetian stage of the middle Devonian.

Wednesday, June 26, 2013

Protoleptostrophia perplana from the Windom shale of New York

Protoleptostrophia perplana is a very thin shelled strophomenid variety of brachiopod. Often the only way one can find and preserve a specimen is when it's attached to a rock surface. Lucky for me this specimen was robust enough to weather out of the rock and be found on a scree field of rock from the Windom shale.

Pedicle valve


Brachial valve


A smaller specimen that popped off a rock I was splitting. The fossil is so thin that light shines through it.

Both specimens were found in the Windom shale member of the Moscow formation (Devonian, Givetian stage).

Monday, June 24, 2013

Strophodonta demissa from the Windom Shale of New York

I was first introduced to Strophodonta demissa via fossils from the Silica Shale in Ohio. Subsequently I have found it in the Widder Formation and now from the Windom shale member of the Moscow formation. I found the below specimen along the shoreline of Lake Erie and it's the most inflated example I've found to date.

 Pedicle valve
Brachial valve

This is the first loose specimen that I've found from the Windom Shale but I have found other examples that are embedded in the rock or broke apart upon extraction. The Windom Shale is dated to the Givetian stage of the middle Devonian.

Saturday, June 22, 2013

Goniatites from the upper Devonian of New York

On a recent trip up to the Buffalo area I chanced across a recent fall along the Lake Erie cliffs. It was rock from the upper Devonian layers that lie above the Moscow formation. The geology is well documented in this area but when you have a random jumble of rock at the base of a cliff it becomes a little more difficult to figure out. As I was exploring the rock fall I found a number of good examples of Goniatites.

Specimen #1

Specimen #2

Specimen #3

Sadly they are not detailed enough to determine species but I did find this passage while reading "Geology and Paleontology of Eighteen Mile Creek", by A.W.Grabau, Buffalo Society of Natural Sciences, Pg. 7,8
 The Gray Naples Shales (Cashaqua shales).-These shales are greenish gray in color, much less fissile than the preceding, and prone to weather into a tenacious clay..... The upper fifteen feet of these shales, while rich in concretions, seem to be very poor in organic remains, no fossils having been noted in them. ... (the beds) forming a prominent band in the main section, is a layer of calcareous concretions, or better a concretionary bed of impure limestone, eight inches in thickness. This probably corresponds to J. M. Clarke's "Goniatite concretionary layer, " in as much as specimens of Goniatites are of common occurrence in it, usually forming the nucleus of the concretion. Several species of Goniatites occur, but they are seldom found in a good state of preservation. They are commonly found in a very much compressed condition, frequently perfectly flattened, and from having been replaced by iron pyrites which subsequently oxidized, much, if not all of the structure is obliterated. The external form and amount of involution therefore become the only characters by which to identify the species, and this, at best, can be but an unsatisfactory identification. In a few cases, in the specimens collected, the septal sutures are shown, allowing a more precise determination. The most abundant and characteristic species of Goniatites in these concretions are Goniatites intumescens (Beyr.) and G.lutheri (Clarke). The non-umbilicated species are rare, a single doubtful specimen having been noted.
Previously I'd thought these to be Gastropods but after reading that passage I am convinced these are Cephalopods. The Cashaqua shale's position in the cliff is above the Moscow formation and so is likely dated to the Fransian stage of the Devonian.

Thursday, June 20, 2013

Cnemidiastrum stellatum from Poland

Following up on my previous post, here is another sponge that I think is Cnemidiastrum stellatum. It is from near Zalas, Poland and is also from the Jurassic (Oxfordian stage) like the previous specimen.

These are views of the sides of this conical shaped specimen.

I'm guessing the large hole on the side is the result of another creature living within the structure of the sponge?

Top surface
Detail of the upper portion

Tuesday, June 18, 2013

Cnemidiastrum rimulosum sponge from Poland

I've not displayed many sponges on this blog with the only other instance being these specimens from the Waldron Shale. Below is a specimen from the Jurassic of Poland. I purchased it from a seller on E-bay. I think it's classified as a Cnemidiastrum rimulosum but I could be wrong.

Side profile
Side detail
Rim detail
Inner surface detail

This fossil came from near Zalas, Poland and comes from Oxfordian stage (Jurassic) rocks.

Sunday, June 16, 2013

Belemnopsis sp. from Poland

Belemnites are a fascinating group of Cephalopods and among my favorite fossils. They looked like modern squid and were related to Ammonites but they had a hardened internal shell called a rostrum. Their (possibly) closest modern relative is the cuttlefish which has a similar internal structure. They were most abundant during the Jurassic and Cretaceous periods and died out about 65 mya. Here are a couple of specimens of Belemnopsis sp. from near Olkusz, Poland.

Specimen #1 is a small guy that I suspect is a juvenile since the fossil tapers more rapidly and is shorter than the other two.

Specimen #2 seems to be a typical size and length. note the divot that runs down the center of the shell surface.

As is typical of many Belemnite specimens this is broken before the phragmocone. Were that intact the shell would be several inches longer. The phragmocone was a hollow area of the shell similar to the chambers of the ammonite shell. It was used to help control buoyancy with a combination of gasses and liquids. Note that the cross section is not perfectly round.

Specimen #3 is the longest of the specimens I have and is interesting because it has oyster spats preserved on it's exterior. In order for this to occur the rostrum would need to be exposed on the sea floor after the organic tissue surrounding it had rotted away. The exposed rostrum then would be an ideal hard surface for an oyster to attach.

 I interpret the dimple in the center of the cross section below as the start of the phragmocone.

These fossils come from rocks dated to the Callovian stage of the Jurassic. There is a really great article posted by Phil Eyden here that goes into much more detail about Belemnites. I thought it was interesting to note that studies have indicated that many Belemnites only lived for a handful of years. This would explain why they are so common in the Mesozoic fossil record.