Need Some Help Understanding Iding

[Raistlin]

Okay, so I am looking at some Ordovician gastropods I am not 100% sure of the formation but I would say I am 85% sure. My problem though is just a slight difference in two books and ID.

The first book I am looking at is Paleozoic Fossils by Bruce L. Stinchcomb. I am using it because I know it covers Smithville fossils and few other books/recourses do. On page 47 of this book it lists the Id like this.

Murchisonia (Turritoma) acrea.

For sure these tall spired gastropods (upper left corner) in these photos are that since they are from the Smithville formation without a doubt.

The other book I am using is Index Fossils of North America by Shimer and Shrock.

Plate 185 shows a photo (black and white) of the gastropod concerning my questions Hormotoma spp. H. gracilis.

On page 457 it lists the fossil linked to that photo as this (I am putting all the information in so that I can figure out what I am looking at).

HORMOTOMA Salter 1859

(*Murchisonia gracilis Hall) High spired shells with many rounded whorls and a sinus in outer lip, and it continues with the descriptiuon pretty similar to that in the Stinchcomb book finishing with Ord., Sil. So I know I am looking at an Ordovician gastropod here as well. Then for that same fossil it finishes the listing like this.

*H.gracilis (Hall) (185-12-17). Ord (Trenton-Richmond): Widely distributed in Canada and the U.S.A.

Here is the fossil in question.

I am almost certain this is Smithville formation though it could be Cotter/Powell. In looking at recourses listing the formation/roadcut I got this from it says that Smithville reminats are pressent at the very top in places. I found evidence that these fossils are coming from the very top of the roadcut. This leads me to believe the fossil is from Smithville formation. Even the coloring (I know that is not an exact science) is like that of the Smithville formation.

Only thing I have found or actually not found proving this to be the Smithville formation is the pressence of the operculum found most often in the Smithville formation.

So my question is what would you list the Id as Murchisonia or Hormotoma sp.? And what is the difference between sp. and spp.?

Thanks for the help.

[squalicorax]

This thesis you might want to try to find or obtain. The Paleontology and stratigraphy of the Smithville and Blackrock Formations of Southeastern Missouri.

There is a taxa list here http://fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=75519

Many gastropods listed. I hope I didnt confuse you more with this list. Also finding that bathyruid trilobite

Edited May 22, 2014 by squalicorax

[Raistlin]

Now that you mention it I do have that as well. lol

It is not a lot of help and does add to my confusion as it seems to list both.

Gastropoda - Murchisoniidae

"Murchisonia (Hormotoma) indet." = Murchisonia

Gastropoda - Hormotomidae

Hormotoma sp., Hormotoma anna, Hormotoma artemesia, Hormotoma confusa

Right now this gastropod is confuse (sorry I had to do it) lol.

So I guess Murchisonia and Hormotoma are interchangeable? That is sort of what I am getting from this.

[ashcraft]

I doubt it is Cotter/Powell, never have seen any fossils come out of those deposits around here. You might try contacting Mike Fix from UMSL. He authored the Smithville paper, and could answer your questions.

fkaa

[Raistlin]

According the Geology along I-55 book the road cuts from 162-168 are Powell and I have seen gastropod imprints in the lower section of the cut (165/hwy TT) which should be Powell. The book also says that on the tops of some of the higher cuts residual material which may represent remnants of Smithville can be found.

But I have yet to see any of the operculums present there. I spoke with Bill about it and he thinks it is possible that it is Smithville but he has only found it as far north as Ozora.

Mainly though I am just trying to figure out if the Murchisonia and Hormotoma are interchangeable. From what I can tell it seems like they might be or am I reading the IDs wrong?

I will try to find a way to contact Mike though and see what he says.

[Raistlin]

I searched the site but could not find a direct contact for Mike Fix. I will see if the contact information they have can get me through to him.

The lower portion of the cut that should be Powell for sure (though now as I understand it they are debating that Powell exists in Missouri and that it is really Cotter) did not have much in the way of fossils. The stuff coming off the top though does seem to have a lot of the high spired gastropods with a few of the flatter gastropods. But I have yet to find the operculum.

This understanding ID stuff is hard lol.

[ashcraft]

Most unfriendly site to navigate.

Finally found faculty/student directory, which did a search and gave me his info.

If you can't find it, let me know and I will PM it to you.

fkaa

[Raistlin]

Yeah go ahead and pm that to me lol. I searched and search and then just contacted the university.

Thanks

[JimB88]

you seem to have two operculum in the first pic...those cap shaped fossils are operculum!

[JimB88]

Ceratopea

[Raistlin]

Yeah those are Smithville for sure. I am pointing more toward the last photo. I am not sure if it is Smithville or not. My main focus though is trying to understand the ID from the two books as well as the thesis.

The way I am reading this is that Murchisonia and Hormotoma are interchangeable. But I could be wrong. The fossil in the last photo has a strong chance of being Smithville yet I have not found the accompanying operculum at that site yet.

[erose]

Not uncommon to have several genera to pic from. In my catalog I have a field called "Identification Reference" where I note what publication(s) I used to determine the identification. I use the simple (author, year) type of notation and all of those can be found in my personal library data base. Sometimes I note things as: Prof, John Doe, personal communication, 20XX if someone else supplied the ID. All of this allows me to go back and double check on things if I find a better specimen or a better reference source.

As much as possible I try and go with the genera and species in the most current reference. I could also go nuts trying to keep up with all the name changes. For example I have not gone back and changed the dozens of Platystrophia I found before Zuykov and Harper (2007). But since then they are labeled Vinlandostrophia.

This all gets even more confusing when a new reference doesn't follow other "new" references and keeps old names in place. Certainly not an exact science in any way at all.

Edited May 23, 2014 by erose

[Raistlin]

That makes sense. I have been in contact with Mike Fix so hopefully I can ID the formation for sure. If it is indeed Smithville I will likely use the Stinchcomb ID.