I’ve been very perplexed by this fossil, but my tenacious curiosity doesn’t give up easily. Follow along as I finally come to a conclusion. To begin with, the mystery fossil possesses obvious meandering ridges resembling the various brain type corals I’ve observed from my Florida collection, yet it possesses numerous deeply pitted openings very much like the encrusting sponge species below, also known to be found in Florida.
The problem with the encrusting type of sponge is that they cover a hard surface such as corals or rocks much the same way in which moss covers the ground. I don’t know enough about sponges to understand if this type of growth pattern would break loose and end up on a beach where my mother-in-law, Winkie, picked it up during the 70’s and 80’s.
If you’ll notice, the “rose brain coral” above has a few pitted holes like the mystery fossil; and if you’ll also notice, the “pink lumpy sponge” possesses a pattern of ridges, but only sort of like it. Hmmmm . . . a point I’d like to make for a second is that’s how fossil hunters learn to observe things as discriminately as they do in order to identify their findings.
So, anyway, we’re on the bloodhound trail, let’s continue observing. On the one hand, the mystery fossil is quite lighter and airier compared to the other Florida corals in my collection and it has more openings visible on all sides which also leads me to think it could be a sponge. Only, the patterns of the openings are similar in shape and size as other coral. I don’t see any distinct differences at any rate. The overall color and texture is consistent with the other corals as well.
In conclusion, if the mystery fossil on most levels appears to be a coral, except mostly for the deep pitted holes, what could have caused those holes and why so many, if indeed it’s not a sponge. You’ve most likely already guessed from the photos of the tube worms above. The clam fossil with the tube worm shells embedded on top of it came from the same Florida collection. The Christmas tree tube worms in the other photo demonstrates how they can dominate the surface of coral. I’m no expert, but I decided the mystery fossil is a type of brain coral which was apparently under attack from several tube worms of one type or another. Feel free to disagree in the comments if you know of think otherwise.
Check out the tube worms link to the right listed under CLASSIFICATIONS to learn more about them and how they can actually be quite pretty.