danu Posted August 16, 2021 Share Posted August 16, 2021 Hey all! I took my little brother out fossil hunting on the lakeshore, I myself am no expert but it's been a lot of fun- we found a number of crinoid and brachiopod fossils and some cool rocks besides. Theres a couple that stumped us though, I've been googling references but nothing looks similar to me. It looked to me like some kind of coral, the second one might just be a rock with some holes in it, but they appear in a fairly regular pattern that intrigued me. Any input is appreciated! Link to comment Share on other sites More sharing options...
Fossildude19 Posted August 16, 2021 Share Posted August 16, 2021 Welcome to the Forum. First is the internal mold of a Rugose coral. Second has an imprint of a rugose coral. Third looks like a tabulate coral. 3 Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
lulufresh Posted August 16, 2021 Share Posted August 16, 2021 The first 2 pictures look like a type of coral for sure but the 3rd pic looks an Ordovician colony of Receptaculites, believed to be a skeleton-secreting algae. Though initially believed to be a type of coral or sea sponge it is now classified as an algae. 1 Link to comment Share on other sites More sharing options...
Mainefossils Posted August 16, 2021 Share Posted August 16, 2021 I agree with @Fossildude19, the third picture looks like a coral. @lulufresh, generally, Receptaculites have small diamond-shaped plates, that are arranged in a double spiral. I don't know whether or not it is a tabulate coral, @TqB would probably know. Nice find, @danu! Regards, Asher 2 1 The more I learn, the more I find that I know nothing. Regards, Asher Link to comment Share on other sites More sharing options...
FossilDAWG Posted August 16, 2021 Share Posted August 16, 2021 As Mainefossils said, recepticulitids have diamond-shaped plates arranged in a double spiral. However, the plates are on the upper and lower surface, connected top to bottom by a column with a circular cross section. If the surface is worn enough to remove the diamond-shaped plates, you will see a series of circular structures. However, they will still preserve the very regular spiral arrangement, which we don't see in the fossil in photo 3. For this reason I do not think it is a recepticulitid. I do think it is a coral. More specifically, this sort of preservation is often seen in corals with a "bushy" (phaceloid) growth form where each individual corallite is a separate tube. A good example would be Syringopora, though there are many others. Often these corals are preserved with the matrix as a solid mass, and the corallites as hollow tubes in which the calcitic coral skeleton has dissolved. Don 2 Link to comment Share on other sites More sharing options...
FossilDAWG Posted August 16, 2021 Share Posted August 16, 2021 Very nice Heliolites! Is that one of yours? Don 1 Link to comment Share on other sites More sharing options...
TqB Posted August 16, 2021 Share Posted August 16, 2021 (edited) 5 minutes ago, FossilDAWG said: Very nice Heliolites! Is that one of yours? Don Sorry, deleted it! Here it is again, Heliolites porosus. Yes, one of mine, but from Morocco. A possible contender, if no. 3 is a body fossil rather than mould. Edited August 16, 2021 by TqB 1 2 Tarquin Link to comment Share on other sites More sharing options...
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