Crinoid Identification? (Jefferson County, Mo)

[calkinsc]

Greetings

I'm definitely an amateur when it comes to fossil identification, and would appreciate any assistance anyone could provide. On Missouri Highway 21, between the Meramec river and the exit for Jefferson College, are a number of road cuts. The cuts closer to the river to about the midway point frequently contain marine fossils, and are fun places to stop and search. One road cut in particular has loose crinoid segments and horn corals. Is there a good reference available on crinoid identification? I have a few fossil references, but they do not go into much detail as to the various types, and I haven't found any web sites that provide sufficient detail, either. Here are examples from that one road cut in particular:

This one shows the typical 5-fold symmetry, as many at that cut do:

http://gallery.calki.../iP1200235a.jpg

This one is also 5-fold, but has more of a central pentagon. Is this a different type, or just more or less mature than one like in the previous image?

http://gallery.calki.../iP1200199a.jpg

Some are very different, though. These are rings:

http://gallery.calki.../iP1200178a.jpg

http://gallery.calki.../iP1200208a.jpg

...and this one has 4-fold (?) symmetry:

http://gallery.calki.../iP1200205a.jpg

These appear to be pieces of calyx, but one is smooth while the other is ridged:

http://gallery.calki.../iP1200193a.jpg

http://gallery.calki.../iP1200232a.jpg

I hadn't realized that there were so many variations in a small sample from there until I took pics with a macro lens - all of these are 5mm or smaller.

Also, a nearby cut has a layer that is a mass of crinoid parts mostly, but the occasional shell (Burlington formation, perhaps?). This is a photo of the rock face, with an oval fossil in-situ. I presume that this is also a crinoid segment, but I haven't come across any documentation on what it is. This particular one is about 1cm long, but I've seen others of varying size.

http://gallery.calki...ir_P1180735.jpg

If anyone could provide info as to what these are, or could point me to references that classify these, I'd greatly appreciate it! Reference after reference that I come across just talk about crinoids in general without acknowledging differences between them (or don't provide enough information to distinguish between them), and there seems to be such a rich variety in even a small area.

Thanks in advance!

Charles

[ashcraft]

I am not aware of any guide book that goes into great details on the crinoids from the formations you are searching. There is one on the Girardeau Limestone that goes into great detail and species description of the crinoids from that formation, which is late Ordovician, somewhat younger then the rock you are looking at. I have a copy of it somewhere, that was missing some pages, so my friend gave it to me. Seems like it is somewhat pricey for a government publication. You can probably find it by googleing Girardeau limestone crinoids.

I suspect Indy will be along shortly, and he is much more familiar with that area then I am.

Brent Ashcraft

[BobWill]

That's interesting to see the stem section with 4 way symmetry. I have one with 6 way that someone said was just an anomaly, not associated with a particular species. Most crinoid IDs I've seen were for mostly fairly complete crowns but there may be some knowlege of distinctions between stems that I'm not aware of.

[Indy]

Several of the outcrops on Hwy 21 are Mississippian in age...Burlington and Warsaw Formations.

I really haven't tried to ID crinoids based on stem segments...However, this one appears to

be Platycrinites which has a distinctive elongated feature. The matrix appears to be Burlington.

Platycrinites stems have a classic twist: LINK

Stem segment for comparison: LINK

Cross-Link (Platycrinites stem segment) post on our forum: LINK

Edited March 16, 2012 by Indy

[calkinsc]

ashcraft - Thanks! I'll try to track it down. Anything that gives specifics is better than what I have now.

BobWill - It may just be an odd one out, though I did find another segment in the same area also with the same symmetry - can't tell if it is from the same individual, though. I did a little searching and found this abstract: http://onlinelibrary.wiley.com/doi/10.1002/gj.3350210407/abstract I don't have access to the article, but the abstract contains lots of 50 cent words that seem to boil down to the fourfold one that they found is either is something new, or it isn't (an "aberrant individual"). I can make the same claim.

Too bad there isn't more identification from stems alone - around here, finding more than disconnected segments, or individual discs, seems to be rare. I've found what are presumably two fairly complete calyxes in the same area. This one also seems to be in the Burlington formation (thanks Indy): http://gallery.calkinsc.com/fossils/images/ir_DSC04528.jpg This one was also found on 21, but at a different road cut than the one I mentioned above: http://gallery.calkinsc.com/fossils/images/iDSC00989.jpg

Indy - Thanks! I've been wondering what those are. We figured that they were some form of crinoid, but we've generically referred to them as "beans" when we find them, Finding them isn't common, although I did just come across another one in a creek in Femme Osage, Missouri last weekend: http://gallery.calkinsc.com/fossils/images/iP1200109a.jpg I don't have the exact size at hand, but it is about half an inch long. We have seen them in the occasional fossil mass found at the Chain of Rocks gravel bar, on the Mississippi River (Madison County, IL).

BTW, how does one identify the Warsaw Formation? Is this the same Warsaw Formation that geodes can be found in? (at least, northward from here, in the region surrounding Keokuk, IA) The area I referred to in my initial post has a lot of chat rock, though seemingly was a cave at one point - found broken pieces of flowstone in the dirt bank I was pawing through. The dirt is reddish, and running fingers through it yields the loose crinoid segments. We've also found a number of horn corals there, which seem... dessicated, if that makes sense for a fossil. Here's the biggest one that we came across: http://gallery.calkinsc.com/fossils/images/ir_DSC04544.jpg This one is in the middle: http://gallery.calkinsc.com/fossils/images/ir_DSC04556.jpg And this one is tiny (5mm or so): http://gallery.calkinsc.com/fossils/images/iP1200190a.jpg

[Indy]

This one appears to be an Uperocrinus...probably Uperocrinus pyriformis

which is commonly found in the Burlington of Missouri