Saturday, May 30, 2020

Spinocyrtia granulosa brachiopod from the Moscow formation

When I think of the brachiopod species Spinocyrtia granulosa the key features are the swept back and slightly recurved pedicle valve and the numerous small bumps or "spines" that can be found on the surface of the shell. This latter feature gives it a granular surface texture that gives the fossil it's specific name. 

Otherwise the shell looks similar to cousins Mediospirifer auducalus, and Mucrosprifier mucronautus with a rectangular wing shaped shell, slightly raised fold on the brachial valve and gentle "u" shaped sulcus on the pedicle valve. The specimens below come from the Windom Shale mbr. of the Moscow formation at Deep Springs Rd., NY.

Specimen #1 - A partial specimen that is missing the "wings" on each side of the central body. Brachial valve
Pedicle valve
Left profile

Specimen #2 - A more intact specimen but it still has some damage. Some might argue that this might be a M. auducalus because of the rounded shell shape but I am calling it S. granulosa.
Pedicle valve
Another angle of the posterior
Right profile
Left profile

Specimen #3 - An isolated pedicle valve that has a nice bit of shell preserved with the granular surface.

 Compare these specimens to examples from the Mahantango formation, Hungry Hollow mbr. of the Widder formation, Morocco, Germany, and Spain.
These specimens were 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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