Stromatoporoids?

[aek]

Hi, interested to hear some thoughts on this fossil found in Chicago. It was chiseled out of a large boulder containing Silurian reef material; rugose corals, gastropods, bryozoans, crinoids, etc... I'm guessing it is a form of stromapotoroids, but I'm not sure. Any ideas? Measures 2.5" 

 

 

 

 

[Fossildude19]

Looks more like a bryozoan to me - something akin to these?

Regards,

[Rockwood]

The diagenetic crystallization makes it hard to be sure, but another possibility is that it is a heliolitid coral. The shapes look perhaps slightly too irregular for zooecia, and the holes show what could have been tabulae. Again, it is not real clear though. 

[aek]

Thanks for the input guys, I really appreciate it! I'm leaning towards heliolites.. strange as it doesn't appear raised off the rock like other corals I've found, though it does appear some tabulae are visible in corallite holes. I'm still a novice to collecting, bear with me...

[aek]

I just came across this heliolitid coral (if that is indeed what it is) freshly revealed from inside the same boulder I found the original fossil above... perhaps these images give a clearer perspective. An odd aspect of the boulder I broke open was the presence of tar... it appears the city basically paved over the majority of the Stony Island outcrops many years ago, strange how the tar oozed inside some of the fossil cavities within the rock.

[Rockwood]

I still don't see the elements that would confirm this as a heliolitid, but they are quite delicate and wouldn't always be preserved. My gut feeling is that it is.

The tar is just passing through on it's way home.

[abyssunder]

Ernst, A., Taylor, P.D., and Bohatý, J. 2014. A new Middle Devonian cystoporate bryozoan from Germany containing a new symbiont bioclaustration. Acta Palaeontologica Polonica 59 (1): 173–183.