March 9, 2019 at 10:07 pm #47106
What kind of productida brachiopods are these?
I collected these productida brachiopods from the Kibbey Formation in central Montana. This group of rocks and fossils are late Mississippian. Location is slightly north of the little Belt Mountains. On Highway 89 north of Riceville Rd.
This type of produtida brachiopod appears to have a bundle of spines projecting from the pedicle and scattered spines projecting from the shell. The spines are very long and about as thick as angle hair pasta. The spines are more or less straight and are as few inches long. The photo shows both the pedicle and brachial valve. The valves many times are deeply wrinkled and folded.
Attachments:You must be logged in to view attached files.March 10, 2019 at 5:35 am #47108Jim ChandlerParticipant
Cool fossil! I am an amateur like you. I did some searching on the web and found an article about brachiopods with spines. Perhaps the author has the knowledge you are after. Also there are some references about identifying similar brachiopods you mentioned. Good luck hunting let me know what you find out.
Jim ChandlerMarch 10, 2019 at 12:28 pm #47167
Hi Jim Chandler,
Yes, I am familiar with the woostergeologist blog and I have read the post on the permian productid brachiopods collected from Texas. Those he writes about are a little younger. With brachiopods knowing the age of the formation where they were collected is really important. But there are a huge variety of brachiopods forming a confusing hay stack of almost look a likes. Ages and locations narrow the possibilities.
Thank for you advice.
David.April 25, 2019 at 7:58 pm #55456
Any chance those might be Echinoconchus sp?April 26, 2019 at 11:55 am #55471
Thank you for your inqury. Based on some research the productida Echinoconchus sp are younger and found in a different region. The examples of Echinoconchus sp lack or do not show signs of spines.
Where as my specimens have spines projecting off the pedicle valve and pedicle opening. These spines are long. I have seen these spines extend a few inches into the matrix. The pedicle valves are very wrinkled. These productida are found in western edge of the late Mississippian age silty shale which are part of the Big Snowy Group. These rocks were once part of the edge of a large sea or tidal lagoon.
If you right click the posted image to view photo, you can them view the image in magnification to see spines and valve details. The photo shows both valves of this type of productida.April 26, 2019 at 2:59 pm #55475
Echinoconchus are quite large and occur is some abundance in the Keokuk Formation in my neck of the woods (Midwest USA). I believe the time frame on that Fm is late Osagean, but I may be off a Stage. Still, that should be similar in age to your stuff. Index Fossils of N America states that spines are present on both valves of Echinoconchus, but are seldom preserved.
Is the Big Snowy Group in the Chesterian Stage?
I for one have never found any Echinoconchus that have the spines preserved. Whatever genus/species yours turn out to be, they are flat out gorgeous!April 26, 2019 at 5:56 pm #55476
Your formation is older. It would be equivalent to the Lodgepole formation which is part of the Madison group in Montana. I also have some Productids from that formation too.
The examples of Echinoconchus I saw were from Kansas coming from Penn age rocks.
The productids in the original post are from the Kibbey formation which is Chesterian late Mississippian.
All of the brachiopods on the plate are produtids. They can grow to a large size. The bachial valve on the younger ones start out flat but then become convex. I have only seen spines on the pedicle vales, never seen the bachial valve. These guys are very fragile. It is likely they are Echinoconchus. I tend to be conservative on identifying brachiopods.
I have a two more plates I am working on now. I collected them yesterday.April 26, 2019 at 9:49 pm #55477
Thanks for the information. The roughly equivalent Formation here in my area would be the Pella Fm, which is Chesterian. The Pella has lots of great stuff in it, but nothing that reminds me of those fabulous productids of yours, that’s for sure.
There must have been shell banks of those things in your area for you to find so many slabs full of them. I still cannot get over those spines!!April 27, 2019 at 8:53 am #55478
There is a strata that contains productids. It rest on a bed of mixed bryozoans. The shale is about 15 feet thick. It rest on a breccia limestone Bed. The breccia is evaporate crusts that were pilled by tidal activity.
In these shale I found part of a plant fossil. I am hoping to find more. So far I have not seen any fish. There are clams and crinoid bits.
Thank you, the specimen above was pure luck.
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