Thursday, May 28, 2020

Grammysioidea alveata pelecypod from the Moscow formation

One of the more common pelecypod fossils that can be found at the Deep Springs Rd. site is Grammysioidea alveata.  It's a subtriangular shell with well rounded posterior and anterior ends. The umbo is large and protruding. the surface of both valves have fine concentric growth lines but also widely spaced and prominent ridges.  This species is similar to Grammysioidea arcuata but is not as long.

Specimen #1 - Right valve
Left valve
Posterior profile - This fossil has been compressed nearly flat.

Specimen #2 - Right valve
Left valve
Anterior profile - Another specimen that has been crushed but this is not quite as bad as the prior specimen.

Specimen #3- Right valve. This specimen is less distorted than the prior two but still shows some compression along the dorsal to ventral axis
Left valve
Anterior profile
Ventral margin

I've found this species in the Mahantango formation of Pennsylvania as well.

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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