Dear forum friends.
I ran Google searches for quite sometime with no success on the matter and knowing that collectively we posses a lot of good knowledge I decided to ask for your help once again. We found this fossil looking slug or leech while hanging out at the beach in Cozumel Mexico a while back. I thought it would be cool to share this find plus We re dying to know something about it so we'd really appreciate any info towards identifying it. If you guys think it is not appropriate for the forum let me know and I will gladly delete the topic. Thanks for your time.

Woah...I have no idea! It looks cool though. 

The ribs almost make it look like a turtle's shell, but it doesn't look like there's a cavity. 

It could also be come strange type of coral...I'm not a marine biologist at all fyi haha 

Thanks for sharing Chris 

Wife found that it is a type of coral. Its a peice of brain coral.

I know exactly what it is.   But. .... I'm going to hold off on saying for wee bit to see what everyone comes up with. 

I know. ... is mean. .... sorry Chris!  Don't worry, I  won't make wait to long. 

I think this is where I insert the evil laugh. .....

I already spilled the beans! !

Cool pic Richard, looks a bit deferent though. We found a lot of the corals also. This one looks very symmetrical and way smoother.
Come on Scott don't be a teaser. ..lol is it a coconut seed or something?

Don thanks for taking a guess , we had the same thought also but like you said it looks solid and possibly a type of sea slug.

It definitely looks like a coral to my eye.  (I've seen fossilized coral here in NJ -- not exactly like that, but similar enough to know the look.)
This may not necessarily be a fossil, especially given that you were in tropical waters.  It could just be small coral head that broke off and has been battered around by the waves and sand for a while.  That would smooth out the rough edges.  Many of the old curmudgeons on the forum will remember "sea glass" -- pieces of broken glass bottles that have been "sandblasted" smooth from being knocked around in the surf for years.  This would be the same principle.  (Plastic bottles don't get polished down in quite the same way...:-(
Cheers,
Jim

 Rose coral.

Picture this coral below with all the sharp edges smoothed out...

 

Ha! Hoosierbanana beat me to it!

You all made me laugh out loud.  Way to go everyone, yes,a piece of brain coral that has been worn down in the surf. There's really not enough left and to difficult to tell from the picsto tell you the species. 

Most likely a young Diploria strigosa.

Way to go Richard ,you got it first. Thanks guys I would have never guessed it was a coral. Scott you knew it all along. Well done , mystery solved! !!

In another life it was kind of my thing.

"Diploria Strigosa" -- Isn't that the spell that Hermione Granger used to turn Lord Voldemort into a fossilized sea slug in the last Harry Potter movie?

needaclone- I have been to Big Brook near you a few times, very abundant shark teeth. The same formation runs down to Delaware and you can find fossils along the C+D canal in the spoil piles. Lots of cool stuff there but not as many teeth by a long shot.

I dunno Scott, looks more like rose coral to me. Just going off the pattern, shape and size of what is left. Chris pointed out that it didn't look quite right.

I'm with Hoosierbanana on this one.
Looks like manicina areolata  (rose coral) or manicina meandrites (maze coral).  And after looking around on the web a bit, it could very well be fossilized...

Hoosierbanana -- Yes, Big Brook is an awesome place. My extended family and I try to get there once a year (give or take).  It's great to have all the brothers/sisters/aunts/uncles/nieces/nephews/cousins digging around in the stream beds and gravel bars looking for the perfect shark tooth (an other fossils).  I don't think we ever went on a collecting trip where we didn't come away with something.  You're right, though....I've been to about 4 other places that are part of the same formation, and nothing compares to Big Brook.

It's possible that it is Manicina areolata, yet not likely unless it was the specimen was imported from Florida or the Bahamas. 

It definitely looks like something related to one of those three, especially if it is a young one that is still had a relatively symmetric pattern.  If it is fossilized, any of those species (or their ancestors) could have had a different range due to different climate conditions (compared to the present day conditions of that location.)

I very nearly caught the "saltwater coral reef tank" bug about 15 years ago.  Man, I'm so glad I didn't.  That would have been so much work.  This fig hobby is SO MUCH EASIER what with all the cuttings and propagating and fungus gnats and potting up and fig shuffling and... ;-D

Sorry guys,having a hard time with the Internet connection lately and it is almost impossible to keep up with the forum. Thanks for the amazing info, I was looking at the brain coral pics on Google search and it is unlikely it is a match. I ll check out the rose and maze corals . Thanks again.

"Brain coral" is a generic term used to describe a vast number of species including rose, maze and many, many more.  With as worn as your specimen in Chris, it will be nearly impossible to positively ID.  Therefore, it is probably better to just leave it as a brain Coral. 

You re so right Scott. I ve been looking at all kinds of pics of corals and they all look amazing. The closest in size and shape that I saw was a couple of rose coral pics but like you said the fact that is been exposed to the elements for who knows how long ,has altered its appearance a great deal. What amazes me is how it feels to hold something this old in my hand !

It is difficult to judge how old the piece is, the coral itself was most likely only 2 or many 3 years old when it died, based off of growth rates of corals I've had that are closely related. Where did you come across the specimen Chris? This could add insight as to it's age and origin.

Oh by the way it definetly is a fossil. It feels more like a solid piece of rock rather than a coral ,in weight and texture!