Pages

▼

Wednesday, November 30, 2011

Vinlandostrophia from Napoleon, IN

While at a quarry near Napoleon, Indiana looking for fossils in the Waldron shale, I had the opportunity to collect fossils from near the Ordovician/Silurian boundary. The quarry was generally mining the Dolomite of the Silurian aged Salamore Dolomite and Brassfield Limestone (Llandovery to Wenlock series) but at the very bottom they had dug drainage ditches into the uppermost Whitewater Formation (sometimes referred to as the Saluda Fm. depending on who your talking too) which is the latest Ordovician (Hirnantian stage, Richmondian local stage). The spoils from this trench yielded a number of brachiopods of the genera Vinlandostrophia (Platystrophia of old). I'm not entirely sure of the species, since there is wide variations and one needs to account for immature individuals as well, but I believe these could be called Vinlandostrophia clarkvillensis.

Specimen #1
Pedicle valve


Anterior

Brachial valve

Posterior

Profile


Specimen #2
Pedicle valve

Anterior

Brachial valve

Posterior

Profile

Note the variation between the two specimens above, are they different species or a single species with variable shell geometry? My friend Herb states that these are Vinlandostrophia ponderosa and that these represent immature individuals. They never got any larger before they died or possibly the paleoenvironment did not allow them enough food and materials to construct the typically larger and more robust shells.

Platystrophia was renamed Vinlandostrophia in 2007 in a paper by Michael A. Zuykov and David A. T. Harper that can be found here.

I based my analysis of the stratigraphy within the quarry on the paper "Compendium of Rock-Unit Stratigraphy in Indiana" by Shaver, Robert H.; Burger, Anne M. published in 1970 by the Indiana Geological Survey. The paper is available from this page (scroll to the very bottom to download the .pdf file).
at

2 comments:

  1. NathanNovember 30, 2011 at 7:04 AM

    These orthids are tough to identify to a species level but one thing I can tell you is it is not Vinlandostrophia ponderosa as those are not in the upper Richmondian Stage which is what the Whitewater is in. http://strata.uga.edu/cincy/strata/cdpRichmond.html
    There is at least 5 species found in the Richmondian and probably more.
    Nice brachiopods though.
    -squalicorax

    ReplyDelete
  2. DaveDecember 1, 2011 at 3:50 AM

    Nathan, I agree that they can be very tough to ID unless you know the stratigraphy or they have some really odd shape. V. cypha is about the only one I can recognize on sight. I'll have to do a post on some of the other species that I've found in the Maysvillian and Richmondian stages of the Cincinnatian.

    ReplyDelete