Hunting the Roadcuts of Indiana's Ordovician

[digit]

And here are two Flexicalymene retrorsa minuens specimens I found that I thought were missing the cephalon:

That explains the two enrolled specimens I found that look just like yours. I couldn't see a cephalon in the field and when I pulled them out of the collecting bag at home to get a closer look under magnification I couldn't see the head parts and couldn't understand how they might have been covered up by the rolling up. Now it makes sense that, much like Washington Irving's horseman of Sleepy Hollow, this one is a little light in the head department.

Liking the images so far--helpful to see named finds from the same areas we collected as it helps with my comprehension of the species I now have in my collection from the area.

Hash plates from the St. Leon roadcut are pretty spectacular with their high densities of Strophomena brachiopods. Many of the pieces that had eroded out from the formation were quite easy to collect--not requiring any tools whatsoever, just selecting whichever pieces looked interesting. One of my favorites is a larger slab with interesting bits on both long surfaces--the edges show that the layers of fossil material are continuous throughout the piece. I showed photos of this one before but I'll repeat those images here:

I wanted this piece to be easily viewable from both sides and so I decided the piece should stand up for display rather than lying down. To that end I decided I would saw off one edge perpendicular to the long plane of the plate so that it would sit flat and balance well. Most of the tile saws available from home improvement stores come with a 7" blade (unless you want to shell out several hundreds of dollars--or more--for a professional model). Because of how the blade is mounted in tabletop tile saws only a small amount of the blade protrudes from above the table allowing material of a maximum of just over an inch to be cut. This is fine for most tiles as they (by their very nature) tend to be thin and flat. Cutting a nearly 2 inch thick hash plate was going to take bigger equipment. I decided to rent a more professional size saw--one capable of taking on thick paving bricks. As we are having a 3-day weekend this year due to July 4th falling on a Monday, I decided it would be a good time to rent a tile wet saw for the weekend. I could pick it up on a Saturday morning (and not have to return it till Tuesday. As most rental stores are closed on Sunday, Saturday rentals will generally give you a free day with the equipment but the holiday afforded me even more time. As it turned out the saw made quick work of what I wanted to do and I was done with what I wanted to do in a couple of hours anyway.

I trimmed several of my larger hash plate slabs by selecting an appropriate edge for the plate to rest on and then determining where I'd make the cut. With the plate clamped onto the sliding table (under a fixed overhead rotating diamond saw blade cooled with continuous streams of water pumped onto either side of the blade) I was able to slowly and steadily make a nice smooth cut along the selected edge of the plates I was prepping for display in this way. Here is how this one turned out:

While I had the wet saw set up I decided to do a little bit of pre-processing work on some of the silicified fossil coral I had collected from the Withlacoochee River back in 2014. I have some nice specimens on display that were very generously cut and polished by John (Sacha) but the bulk of the material I chipped into smaller pieces with a hammer and I've been tumbling those into nice smooth forms with a high-capacity rock tumbler that I bought for this very purpose. I've already run through several loads of this chalcedony "chert" material and formed some nice looking pieces. Some of the chunks of this silicified fossil coral resisted being reduced to smaller sizes by smacking it with a hammer and so I wanted to turn to a wet saw. The best way to reduce this material to smaller pieces for tumbling is to break off smaller shards by whacking corners and edges with a hammer--much in the same way that the Native American craftsman would have done to produce preforms to knap projectile points and other sharp instruments like knives and scrapers (though my disassembly of these coral chunks took significantly less skill). Smacking smaller chunks of this rock to try to break them up doesn't work very well and generally only ends up creating cracks in the material that are often visible in the final tumbled pieces. For this reason I chose the slower and more precise method of slicing up some material on the wet saw. This chert material is very hard and so as to not overtax the diamond impregnated saw blade I moved through the material at a very slow rate. In a couple of hours I was able to trim several hash plates and prep my remaining cache of chert pieces that will keep me tumbling for several more loads.

Cheers.

-Ken

[digit]

While doing a little internet research on this great area for fossil collecting, I came across this most excellent overview that was put together for a roaming field trip of university students back in 2013. I'm sure that all of the folks who are already quite knowledgeable in the taxa and localities of the Ordovician outcrops of the Cincinnati Arch have probably seen this publication already but for the benefit of newbies like me, I'm including a link here as I think this paper has some really great information in it:

http://opus.ipfw.edu/geosci_facpubs/82

Cheers.

-Ken

[digit]

I did find this:

Edrioasteroid.jpg

It doesn't quite look like the photos in my book, but I think it's a juvenile edrioasteroid! On a piece of Rafinesquina shell. It's certainly smaller than the edrios I've seen before (at rock shows; this is the first I've found), and I can imagine that the usual structure might develop with size. This one is just under a 1/4 inch across.

I'm quite uninformed about the fossil fauna of the outcrops in this area (certainly different from the much younger fossil material I normally encounter in South Florida) but I enjoy picking up on interesting things like this and then delving in to learn more about things that interest me. I call this randomly non-linear chaotic form of learning bits and pieces "tangential learning" where I allow myself to go off on a tangent and investigate more about some new topic that has come to my attention. I'll take a deep plunge and get a good overview for a particular topic before moving on to something else that catches my attention. It could easily be termed ADHD learning but I like my term better. I'm trademarking it now so you owe me a quarter every time you use it from now on.

While looking more into edrioasteroids I came across the paper in the link above. On the same page of that paper where they show a drawing and a photograph of an edrioasteroid, they give examples of many of the other echinderm taxa that might be encountered in the area. I found the Cincinnaticrinus pentagonus crinoid of which we found many column segments and also saw the species Plicodendrocrinus casei which seems to have a much more 5-pointed star shape in cross-section. While looking at your likely juvenile edrioasteroid on a Rafinesquina photo above, I spotted a few markings where it appears Plicodendrocrinus stem segments may once have been located. I can see what appears to be a star shaped outline with the pentagonal inner contour visible. I could be totally wrong on this ID but then that would just lead to another opportunity for learning so win-win either way.

Looking forward to seeing more of your material from the later two stops of the day.

Cheers.

-Ken

[erose]

Some of your Hebertellas may be Plaesiomys.

The edrioasteroid is an excellent find and ;looks to be well preserved. I believe the two star-shaped items are crinoid holdfasts, not column segments and are another special find. That one piece alone would have made my day!

Good stuff!

Edited July 3, 2016 by erose

[Mediospirifer]

Thanks, everyone! I do agree that I have some good pieces. Especially the edrioasteroid with its associated epifauna! That one's going into a gemjar, as are the F. retrorsa minuens. The star-shaped markings (I've spotted 3; there's one on the extreme left edge visible in the photo, too) are holdfasts, I think, and may be Plicodendrocrinus. I don't have a good reference for crinoid stem ID yet.

Speaking of F. retrorsa minuens, here's photos of both sides of my complete specimens:

If you look closely at the bottom edges, you can make out the tip of the glabellas. The heads weren't visible until I had (carefully) cleaned them with a toothbrush and water.

digit, I like your slab! Good job with the saw; I've never worked with tile or rock saws, just wood.

[doushantuo]

Marvellous stuff,Medio,Digit.Mouthwatering hash plates!

[Tidgy's Dad]

On 6/12/2016 at 3:35 PM, Grimlock said:

First off, HAPPY BIRTHDAY Ken I'm glad you had a good adventure up there. Now you got me wanting some deep dish pizza.

Yes, a slightly belated happy birthday, Ken. 

[Tidgy's Dad]

On 6/20/2016 at 12:24 AM, digit said:

 

I found one brachiopod with some smaller fossils attached to the shell. I'm wondering if these might be the Tentaculites that I learned about from Mediospirifer?

Cornulites flexuosus, I think. 

Great thread. 

As you probably know, Lepidocyclus capax is now Hiscobeccus capax which is generally smaller and with fainter growth lines than Lepidocyclus perlamellosus found in the same beds. Both seem to have been posted here.

[digit]

9 hours ago, Tidgy's Dad said:

Cornulites flexuosus, I think. 

 

Seems to be a match: https://strata.uga.edu/cincy/fauna/tentaculitoidea/Cornulites.html

 

" Cornulites has traditionally been considered a polychaete tubeworm, but its internal structure suggests that it is allied with the tentaculitids, which may both belong within the phoronid worms (Vinn and Motus, 2008)"

 

I love modern day phoronids. They are often mistaken for polychaete tube worms but their radioles (feather-like feeding/respiration appendages) look different and they are more often found in clusters in soft substrate.

 

 

Cheers.

 

-Ken

[Tidgy's Dad]

1 hour ago, digit said:

 

Seems to be a match: https://strata.uga.edu/cincy/fauna/tentaculitoidea/Cornulites.html

 

" Cornulites has traditionally been considered a polychaete tubeworm, but its internal structure suggests that it is allied with the tentaculitids, which may both belong within the phoronid worms (Vinn and Motus, 2008)"

 

I love modern day phoronids. They are often mistaken for polychaete tube worms but their radioles (feather-like feeding/respiration appendages) look different and they are more often found in clusters in soft substrate.

 

 

Cheers.

 

-Ken

Yes, very interesting, especially as many recent researchers are tending to place the phoronids and tentaculitids into the lophophorata, often as closely related 'sister-groups' to the brachiopods.