This microfossil appears to be a Chiracanthus sp. fish scale. The field of view (FOV) is about 2 mm. It dates to the Devonian Period. The fossil was found in the Beechwood Limestone of Clark County, Indiana USA.
Thanks to Kenny for the image.
Learn more about the Chiracanthus at: https://en.wikipedia.org/wiki/Cheiracanthus
