Platyostoma gastropod and Stereolasma coral from the Mahantago

As I'm parsing through my findings and cataloging the pieces I want to keep, two new species will joining my collection of fossils from the Mahantango Formation of Pennsylvania.

The first is this internal mold from the gastropod Platyostoma (Nanticonema) lineata. It is somewhat intact and free of any distortion unlike some fossils found in nearby exposures in the same pit.

...and this partial rugose coral that I think is Stereolasma rectum. All that I found is this little stump with septa converging on the interior

and what may be septal grooves on the exterior. I wish I could have found the rest of this guy as rugose corals are somewhat rare in the Mahantango.

Both of these specimens came from an exposure of the Mahantango Formation (Devonian, Givetian stage) near Liverpool, PA.

Chonetes sp. brachiopod with spines from the Mahantango formation

Chonetid type brachiopods are fairly common in the Mahantango formation on Pennsylvania but a recent find deserves a little more notice. It's a shell with small spines preserved coming off the posterior hinge. Only three are visible, the yellow iron staining helps set them off, but this is a somewhat unusual occurance based on my experience. Most all the fossils found in the Mahantango are the results of storm deposits, very few are "smothered bottom" type. As such delicate details like the spines are often lost when the original shell is tossed in the waves.

I collected the above specimen was collected near Seven Stars, PA from the Mahantango formation (Devonian, Givetian stage).

Modiomorpha pelecypod from the Mahantango

I have posted some specimens of Modiomorpha from the Mahantango formation before but this specimen is different in that there is some shell material preserved. It's not the original shell but more likely a replacement by Calcite.

The shell cast is not complete but this is still an uncommon occurrence from the Mahantango formation (Devonian, Givetian stage) since I often find the weathered, leached molds of pelecypods. This specimen came from near Liverpool, PA.

Some gastropods from the Mahantango formation

I'm going through some boxes of findings from the Mahantango formation (Devonian, Givetian stage) and came across some decent gastropod fossils that I found at Liverpool, PA.

This is a Cyclonema mold in matrix with a little bit of the exterior shell cast intact. There is also a Nucula varicosa pelecypod just above and to the right of it.

Then there is this mold from the internal chamber of a gastropod. It's tightly coiled and the whorls stack internally rather than rise up like most snails fossils I've seen. It seems to be a fairly wide living chamber and the width of the whorls increases rapidly unlike the Goniatites of the era.

Here you can see the groove where the whorl pressed against the previous shell area.

Maybe this is a Straparoullus or Tropidodiscus? With the small amount of info that I can find online I'm leaning towards Tropidodiscus.

Fossil branch from the Mahantango

Being that the Mahantango formation is Devonian in age, more specifically Givetian stage, it is not uncommon to find pieces of pyritized branches. Sometimes they can be a bit difficult to ID as fossil wood because they are thin and often could be confused with worm burrows. On a recent trip to Deer Lake, PA I found a piece with what I believe is unmistakably a fossil branch. On the specimen below you can see the brown-orange staining from the breakdown of the pyrite which is the first clue.

Next is this closeup which shows a branching structure that could be the remains of a rachis (central vein to which the pinnules of leaflets were attached in tree ferns).

Lastly is the patten of the preserved structure which is entirely different from the surrounding rock. It looks striated and rough where as the rock is smooth and homogenous.

I could still be wrong and this is actually a worm burrow. There are no other preserved "rachis" which should be regularly spaced along a main branch. On the other hand the fossil is very straight with no obvious undulations that might be the result of the worm moving through the sediment.

No matter what this is an interesting specimen and makes one think about the paleoenvironment that it was deposited in.