Bird Feet, Bird Tracks... Or Something Else Altogether

[jordanbbates]

Found this rock on Lake Michigan along the Frankfort shoreline. I thought it would be fun to experiment with some acid, so I put it in 10% or so bath for a day. I washed it off this morning and viola... little bird feet! Or, foot prints. Or maybe not. This area was a tropical, shallow sea for a long time, so maybe bird prints don't make sense. Also, other than the ID of this... I wonder how common this is?

Any help would be appreciated.

[Fossildude19]

Sorry, but according to this Bedrock geological map of Michigan, your area is Devonian or Mississippian in age - too early for birds or dinos.

I think the acid has eroded away either some brachiopod fossils or a bryozoan, maybe something like Evactinopora.

Think ancient seafloor when looking in your area - brachiopods, pelecypods, gastropods, trilobites, corals, bryozoans, etc.

Keep looking.

Regards,

[tmaier]

I see something at the bottom of those "prints". It looks like they are molds and some of the original objects are still in there.

[jordanbbates]

Sorry, but according to this Bedrock geological map of Michigan, your area is Devonian or Mississippian in age - too early for birds or dinos.

I think the acid has eroded away either some brachiopod fossils or a bryozoan, maybe something like Evactinopora.

Think ancient seafloor when looking in your area - brachiopods, pelecypods, gastropods, trilobites, corals, bryozoans, etc.

Keep looking.

Regards,

Looking at the Evactinopora images on Google... this angle makes me think you are spot on with your guess. http://www.lakeneosho.org/Evactinopora/images/Morphology/2thumb.JPG

[TqB]

I think they're brachiopod interiors with a strong median septum - you can clearly see the outlines of the thin outside shell.

[Fossildude19]

I agree with Tarquin - My first thought was brachiopod as well.

See the attached pic:

Regards,

[jordanbbates]

Very cool. Thank you.

[Auspex]

Internal molds of brachiopods, IMO.