Thursday, April 30, 2020

Goniophora hamiltonensis pelecypod from the Moscow Formation

The large shell of Goniophora hamiltonensis is easy to recognize but the trapezoid shape with a rounded anterior end and an angular posteior end with two straight edges that almost meet at a 90 degree angle. This specimen is somewhat 3D in shape so the ridge, that angles down from the umbo to the margin where the straight edges meet, is very prominent.  Concentric growth lines finish off the decoration on the shell exterior.

Looking down the ridge

This specimen has a few interesting features that I interpret as worm tubes and an inarticulate brachiopod that lived on the interior of the shell as it lay on the seafloor. My interpretation of this is based on the presence of linear bumps that have the concentric growth lines passing over them. the roundish blob that is near the ridge of the shell look like the cemented brachial valve of a Petrocrania sp. type inarticulate brachiopod.  All of these interpretation make me think that this fossil is a cast of the original shell.

This specimen was found at a borrow pit on Deep Springs Road in Madison County, NY which exposes the Windom shale member of the Moscow formation (middle Devonian in age, Givetian stage.)

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