Howellella (?) from the Keyser formation

This fossil is from the Keyser formation but I'm not entirely sure of it's name. I think it's a Howellella but it could also be Megakozlowskiella, Delthyris or some other Spirifer. All are known from the Keyser so ID is difficult.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

The Keyser formation is Silurian to Devonian in age (Pridoli to Lockhovian stage).

Gypidula from the Keyser formation

Another new brachiopod for me from the Keyser formation is Gypidula. This comes from the same location and the Whitfieldella and Meristina I posted about before. I distinguish this from Whitfieldella by the lack of a sulcus.

Specimen #1
Pedicle valve (with small bryozoan colony)

Anterior

Brachial valve

Posterior

Profile

Specimen #2
Pedicle valve

Anterior

Brachial valve

Posterior

Profile

This specimens shown above came from the Keyser formation which is dated at the boundary of the Silurian (Pridoli stage) and Devonian (Lochkovian stage).

Whitfieldella from the Keyser formation

From the same exposure as the Meristina brachiopod I blogged about a few weeks ago comes this Whitfieldella sp. brachiopod. It's a fairly large fossil with a clear sulcus or "divot" down the middle of the pedicle valve. superficially it looks similar to a Meristina but it's longer and not as wide.

Pedicle valve

Anterior

Brachial valve

Posterior

Profile

The Keyser formation is grouped across the boundary between the Silurian (Pridoli stage) and Devonian (Lochkovian stage) so it's hard to know exactly what ages the rocks are that I found the fossils in.

Meristina brachiopod from the Keyser limestone

This is a brachiopod I found in an exposure of the Keyser formation called Meristina. It's fairly plain and featureless except for the sulcus.

Pedicle valve

Anterior

Brachial valve (weathered)

Posterior

Profile

The portion of the Keyser formation that I found this in is thin beds that are fairly shelly but have lots of complete specimens. This would indicate to me that it was a low energy reef like environment. Interestingly enough there are few bryozoans, coral or stromatoporids, which are typically the reef builders, in the same layer. So far I've not found any brachiopods in life position so it could represent a "pavement" or sorts that was periodically buried.

Eccentricosta from the Keyser formation

At one locality where I collect from the Keyser formation I've found an interesting brachiopod called Eccentricosta. That name is was created in 1963 as a way of moving fossils called Chonetes jerseyensis into it's own genus away from Chonetes. This was done due to significant differences in some of the shell anatomy such that it deserved it's own genus. There is a paper that explains how and why this was done available from JSTOR.com

Now onto the specimens! The shells that I have found all have been partially buried in the rock. This first specimen I cleaned off with a wire brush to expose it more. I can't tell if it's a pedicle or brachial valve though. The most telling feature are the radial ribs that decorate the surface.

Specimen #2

Specimen #3

Specimen #4

These fossils are fairly rare though as I read reports about the Keyser formation there is mention of zones that are traced via this fossil. I'm still learning how that works but I think faunal zones are designated by somewhat rare or unusual fossils.

Possible Hexactinellid sponge from the Keyser Formation

Another strange item that I've found in the Keyser formation are these fossilized "threads". I've found several instances of these fossils and they do not look like a geologic phenomena. When viewed normally they look almost like grass, leaves or wood but that is not possible as the Keyser formation is upper Silurian to lower Devonian in age and plants were not yet that developed.

A closer look reveals a definite fibrous structure and lack of layering. The "threads", as I call them, overlap and diverge from one another seemingly at random.

Another specimen with good examples. This has been polished a little by my Dremel tool to see if any other details emerge. I was starting to think they were fossilized algae or trace fossils.

I'm truly stumped by this one so I went to the Fossil Forum to see if anyone else recognized what they were. The general consensus is that they could be some root structures from a Hexactinellid sponge. There is a lack of good information on the fauna of the Keyser formation and so I'm still trying to determine if there are any known Hexactinellid sponges that have been found within it. I've found Stromatoporid sponges in the Keyser formation before and blogged about them Here and Here, but they don't have root structures; instead preferring to encrust and form mound like shapes. If anyone has any ideas please let me know.

Possible Cystoids from the Keyser formation

While searching an exposure of the Keyser formation near Mt. Union, PA I found some odd rounded objects.

I think they may be Cystoids but when I found them they had no discernible markings. Thinking them to be chert nodules I soaked them overnight in some vinegar and that is why they look a little etched. It wasn't until I got a closer look at the etched pieces that I noticed what looked like a pattern of plates. You can see what I am talking about in the specimen below.

As you can tell from the pictures above it seems to have a diamond shaped cross section so maybe that represents a top and bottom. I do not see any clear evidence of a stem or arms though. At this point it looks like the pattern may be an internal mold of a Cystoid or Crinoid but I doubt I'll ever be able to ID it since there it little to go on.

The Keyser formation is upper Silurian to lower Devonian in age (Pridolian to Lochkovian stage).

Orbiculoidea

Orbiculoidea is a genera of inarticulate brachiopods that are common throughout the paleozoic. Despite this I have not found many here in Pennsylvania. Not long ago I was exploring some abandoned limestone quarries, with permission of the current land owner, in Montour county that exposed the Keyser formation and I found some rather large examples.

All are partials but the interesting thing is that the shell is preserved as a dark color against the lighter host matrix.

Note the concentric growth rings and the (implied) terminal tip of the shell offset from center.

Specimen #2

Specimen #3 has the least complete shell but the most well defined growth rings.

Based on the shape and growth pattern these shells all look like they are inarticulate brachiopods, however could they possibly be a monoplacophoran instead? Monoplacophorans are gastropod like mollusks which have a cap shaped shell rather than a spiral shape. I'm not sure if they are known from the Keyser formation due to the lack of good information regarding the fauna found within the formation. The Keyser formation is upper Silurian to lower Devonian in age (Pridoli to Lochkovian stage).