Monday, May 18, 2020

Retispira leda gastropod from the Moscow formation

Retispira leda is a Bellerphonid type gastropod that had a large, conispiraled shell with a wide flaring "skirt" at the front aperture of the shell. The shell must have been thin walled as I most often find it crushed nearly flat.  The key features that help to ID this fossil is the central rib that shows concentric, back curved growth lines. That and the cross hatching present on the rest of the shell, the results of linear striae running along the direction of the shells growth crossing concentric growth lines. The first specimen below has some of the flaring aperture intact while the second does not.

Specimen #1 - ventral view
 Dorsal view - at the top of the specimen you can just see the shell as it curves over the edge and continues spiraling under itself.
 This view shows you how flat this once bulbous shell looks now.

Specimen #2  - ventral view

Dorsal view - this has less matrix obscuring the coil
 A view of the now squished shell from the side.

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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