Hederella filliformis on a Sterolasma coral from 18 Mile Creek

As you walk along the shore of Lake Erie, next to the cliffs, you will find quite a few examples of the rugose coral Sterolasma rectum eroded out of the rock. This particular specimen features some Hederella filliformis bryozoans encrusting it's surface.

Note in the above picture how the Hederella grows facing down while the coral grows facing up. What I think this represents is the coral being tossed by waves until the calice is embedded in the mud. This could have happened after the coral had died. Once in it's new position the Hederella colonized the surface and grew in the direction of the currents where it would have a better chance at catching food.

Here is a closer view of the Hederella colony that I cobbled together from several shots that I took with my Zorb microscope camera.

The rest of the coral is barren but a very good example of Sterolasma rectum.

The calice is well exposed and somewhat intact as well. Most specimen I find have much of the calice walls broken off as they are somewhat thin and fragile.

This specimen likely came from the Wanakah shale (part of the Ludlowville Formation) which is middle Devonian (Givetian stage) in age.