Wednesday, August 11, 2010

Pholidostrophia and Ambocoelia

While I was in NY this past spring I collected from the Wanakah and Moscow formations and found two Brachiopods that were new to me: Pholidostrophia and Ambocoelia. As the formations are concurrent with the Mahantango I was very happy to add them to my knowledge of the Middle Devonian.

Pholidostrophia is another member of the class Strophomenata and is most easily recognized by it nacreous shell when first exposed. These specimens came from the Wanakah Shale exposed in the cliffs along the shore of Lake Erie near the mouth of 18 mile creek.

This first piece has the nacreous shell in place.

These next two don't have any of the shell material left but looked golden (due to pyrite replacement) when I first broke the rock apart and found them.

Ambocoelia is a member of the Spiriferida order, although to me it looks more like a Productid. It's a shell that has a large pedicle valve and a flattened brachial valve. In some parts of the Moscow and Wanakah formations these brachiopods can be found in huge concentrations. In fact there is a bed at the base of the Windom shale member of the Moscow formation that is 8 inches thick and packed with Ambocoelia. I believe these next couple of specimens come from that layer since they were collected at Cazenovia Creek in an area that likely is the base of the Windom shale.

Here is a cluster of specimens

A single shell that is inverted in the rock and exposing the brachial valve

Some good pics of individual specimens (they are tiny and my pics didn't turn out), check out the first picture on Karl Wilson's page of Brachiopods from the Windom shale.

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