Saturday, July 11, 2015

Costellirostra singularis brachiopod from the Kalkberg formation from New York

I don't have any specimens that are free of the matrix of this next fossil , but they do occur in profusion in some layers of the Kalkberg Formation. It's a brachiopod called Costellirostra singularis and is fairly distinctive. The shell is ovate in shape and wider than long. The pedicle valve is convex around the beak and concave towards the margins with a prominent fold or sulcus. The brachial valve is convex and, when viewed from above or embedded in the rock, appears like it has three lobes as in the below specimen.

In reality it is a view that highlights the strong strong fold on either side of a central "ridge".
The other distinguishing features of this species are the very fine, radiating striae that decorate the surface of the shell.

Here is a specimen that is mostly free of the matrix. Brachial valve
Pedicle valve

As I indicated above, some layers of the Kalkberg formation have a profusion of this species and many are distorted or flattened.

Compare these specimens to Costellirostra singularis that I found in the Licking Creek formation of Virginia.

The Kalkberg formation is lower Devonian in age (Lockhovian to Pragian stage). I collected these specimens from a roadcut near Shoharie, NY.

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