Thursday, July 22, 2010

Ptylipora sp. bryozoan, not Plumalina? from the Mahantango formation

Edit 11/17/15: Thanks to Steve Pavelsky, who commented on facebook regarding these fossils, for recognizing them as the rare bryozoan, Ptylipora sp. (possibly striata).

I was doing research for a trip up to NY and Ontario last April and was reading through Karl Wilson's excellent website "New York Paleontology" website and I came across a page talking about the Hoxie Gorge. On the page they talk about a rare fossil that is relatively common at this site call Plumalina. As I was reading and looking at the pictures I realized that I'd found something similar twenty years ago when I was a kid exploring a local Devonian Mahantango formation exposure. I'll go into more detail about the site another time but here is the fossil:

Here is a pic from the aforementioned website for comparison:

You can also see some superb pics on this Flickr page: Click Here

Seems that this might have been related to Hydrozoans. I'd previously thought it was part of a Conularia but it doesn't look right. I even asked someone at the Smithsonian to take a look at it years ago but they said there wasn't enough to make a determination.

Recently I think I found another example of this rare fossil in the rocks of the Mahantango formation (Centerfield member) near Stroudsburg, PA. This specimen is a faint impression that is best seen with the light at an oblique angle. Below are pictures of the specimen taken from different angles to highlight the herringbone like structure:

I don't think these are Crinoid pinnules as they are much too long and unsegmented. Maybe they are leaves that are partially decomposed? At any rate, it is interesting how one can recognize a fossil that is in their collection just by looking at other people's pictures.


  1. Those first ones... nice! While the spacing of the "pinnules" appear to be more dense, it sure looks similar. As you know, I'm not much of a plant guy, but the latter ones appear to be plant like. In Plumalina, there is a chevron pattern that appear to be missing in your recent finds. I was thinking some kind of lycophyte???

  2. I meant to ask: what is the depositional environment?

  3. Solius, These come from a deltaic environment. The first specimen is in a sandy siltstone while the second is more of a limy siltstone. Geographically they are 15 miles apart but are in different horizons of the formation. I haven't quite worked where and when yet though.

    I see something of a chevron pattern in the last specimen, close to the base stem, but it is not as well defined as the first specimen. I'm still skeptical about the first being Plumalina as the depth of the fossil is more than I would expect for a soft bodied creature. Then again, there is no obvious segmentation or other structure to prove otherwise.