Monday, November 22, 2010

Orthostrophia strophomenoides

After a month to catch up I am starting my regular blog posts again with a series of ID posts concerning the fossils found in the Haragan formation of Oklahoma. Most of the specimens that I will be illustrating have come from an old estate collection and it's taken me many hours of research to ferret out the names of the many different fossils. The Brachiopods are the easiest since there are whole volumes describing them and their distribution in Oklahoma by the Oklahoma Geological Survey. So without further ado I will start with Orthostrophia:

Orthostrophia (Hall 1883) is fairly common genera in the Haragan Fm. and is found in great numbers at the famed site known as White Mound. The specimen pictured below is likely the species O. strophomenoides based on the book "Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region" 1958 Thomas Amsden and Arthur Boucot, Oklahoma Geological Survey, Bulletin 78 pgs:41-45.

Brachial Valve


Pedicle Valve



The name of this genera tends to throw my mind for a loop because most shells (that I've studied so far) with "strophia" in the name tend to have convex pedicle and brachial valves. This specimen came from an old estate collection of fossils that were collected in the 1960's to 1970's from the Haragan Formation at White Mound, OK. The Haragan formation is thought to range from the upper Silurain, 418mya, to the lower Devonian, 411mya ( Pridoli to Lochkovian). This would correspond to the Birdsong shale of Tennessee and the Helderberg Fauna of New York, Pennsylvania and Maryland.


  1. Welcome back!

    Do you think the brachiopod in this post is also an Orthostrophia?

    I used the Ancient Shells at the Falls of the Ohio Part I: Brachiopods to determine that fossil's name.

  2. No, I think you have a Orthospirifer, not an Orthostrophia. Orthostrophia is pretty much extinct by the middle Devonian.

  3. Oh and thanks for the welcome, Mike! I can't keep up with the rate of posts that you do. But I'm trying my best. :)

  4. The brochure I referenced earlier refers to the same brachiopod (shown in the brochure in Figure 2) as both an Orthospirifer and Orthostrophia. So that appears to be a mistake.

    Thanks for clearing it up.

    While I have the quantity of posts you surpass me on quality/content of posts.

  5. Hi Dave, welcome back! As I'm sure you know, the "stroph" refers to the hinge of the critter. Think of the strophomenids; they are generally highly strophic, but plano, or concavo, convex.

    Here, they are common, and I rarely pick them up. If you would like some, shoot me an email at solius "underscore" symbiosus "at" yahoo "dot" com and I will send some.

    Cheers, Tim