Halysites (?) specimen

[LisaL]

I found this pretty little chain coral in southwest Michigan glacial drift a couple of days ago. I'm interested in whether it's possible to narrow the ID down between a Halysites species or another genus, like Quepora. My simplistic understanding is that coenenchymal tubules would indicate a Halysites species, so that's what I've been focusing on, although I know there are many other indicators, like size and shape of corallites. size of ranks, shape of luminae, structure of longitudinal tabulae, etc. This piece is probably too silicified to tell without thin sections, anyway, but I thought I'd throw the pics up, in case there's a coral person here who can help me interpret any diagnostic features they see. (The tape measure I tried to hold up in the last photo is cm)

 

Many thanks!

 

 

 

 

 

 

 

 

 

Edited June 4, 2019 by LisaL

[FossilDAWG]

This is almost certainly a Halysites compactus Rominger.  The short chains (2-4 corallites) and correspondingly small lacunae are characteristic.  It is certainly not a Quepora; as far as I know that genus, which has spine-like septa, is found only in the Lake Saint John area of Quebec.  Halysites compactus is widely distributed in northern Michigan and adjoining areas; I have collected it in the Lake Temiskaming area (Ontario and Quebec border).  

 

Don

[TqB]

Great specimen and photos - I agree with @FossilDAWG.

It's a new one on me so I checked the Treatise. It is now Hexismia compactus, the type species of the genus.

The main characteristic of Hexismia Sokolov, 1955, is the halysitoid corallum "but with single corallite ranks, each corallite either in contact with several neighbouring corallites or connected to them by coenenchymal tubules".

 

Here's the Treatise illustration (the lectotype) - relatively wider corallites than yours but I don't think that matters.

 

 

[Tidgy's Dad]

Very nice find! 

That's a great specimen and a good id by the chaps, I think. 

[LisaL]

Thank you so much, Don and Tarquin!

 

I had noticed Hexismia under its old name in a Yale-Peabody museum brochure from the 1950s, but I sort of brushed it off, because the corallites in the bulletin's example looked "too" compact, with almost no ranks or luminae at all. One of the example specimens in the bulletin even looked similar to Favosites, the corallites were so tight! (Here's a link to the bulletin. And here's the photo that reminded me of a favosites, figures 5-6):

 

 

Maybe the corallites in my piece are just spread out a tiny bit more. I don't see them touching each other very much, and my eye keeps seeing groups of 3-4 corallite 'petals' that appear attached by a filled-in white silicated center (like a flower stamen). This pattern just looks so different from the "single-corallum ranks" in the Treatise photo. (Don mentioned ranks of 1-4 corallites associated with this genus, though, so maybe I'm just being too literal minded.) Also, the Treatise photo has those obviously smaller coenenchymal tubules squished around the larger corallites. I'm having a hard time seeing those in my piece, unless they're just covered under the white silica. Even with those misgivings, Hexismia is definitely making sense, especially since it's known from northern Michigan!

 

The Treatise does mention Kentucky as a location for Quepora in North America, along with Quebec. So I guess it's *possible* for it to occur in Michigan, since the rocks in upper Michigan correspond in age with the Silurian rocks of Kentucky.

 

But then there's the issue of Quepora's spine-like septa (which I siuppose could be lost in silicification here?)

 

At any rate, I think your two suggestions of Hexismia say a lot! (Plus, Tarquin, our friend Asa on the Facebook group also mentioned that Hexismia looked very interesting, before I told him your suggestion.)

 

It's so nice to have a name to place with this little piece. I appreciate it very much! If I find out any more information, I'll update this post.

 

Lisa

 

Oh,  I just thought of something else. In the 1955 Yale-Peabody museum bulletin, there is a picture and description of a species called Halysites encrustans. I thought this might be close to what I have, with its wider lacunae and smaller corallites, but this is supposedly an encrusting species, and the only location is Quebec. (Shoot, and they also have septal spines.) I can't find this name anywhere else online or in the Treatise, though. It must have been moved to another species?

 

 

Edited June 4, 2019 by LisaL
added URL

[LisaL]

3 hours ago, Tidgy's Dad said:

Very nice find! 

That's a great specimen and a good id by the chaps, I think. 

Thank you so much! I'm glad I thought to post it here.

 

[hemipristis]

oooh, very nice!!

[TqB]

Excellent response, @LisaL.

I agree that the geometry of your specimen and the Treatise photo are different, and the H.encrustans approaches it from the opposite direction. So whether it could be regarded as a variant of one of them or a different species needs more investigation and comparative material. Or maybe there's only one variable species?

Also, Quepora is described in the Treatise as having "septal spines absent or poorly developed" - and I can see a few short ones in yours...

 

Thanks for making me look more closely!

[LisaL]

9 hours ago, TqB said:

Excellent response, @LisaL.

I agree that the geometry of your specimen and the Treatise photo are different, and the H.encrustans approaches it from the opposite direction. So whether it could be regarded as a variant of one of them or a different species needs more investigation and comparative material. Or maybe there's only one variable species?

Also, Quepora is described in the Treatise as having "septal spines absent or poorly developed" - and I can see a few short ones in yours...

 

Thanks for making me look more closely!

Tarquin, thanks so much for taking the time to look closely and to share your thoughts with me! It didn't occur to me that I could have a variant of one of those species. (And I thought I was seeing a few septal spines, too, so thank you for mentioning it.)

 

I've just discovered that my local university library has a partial collection of the Treatise, so I've had huge fun the past couple of days learning how to read it and browsing volume F. Your comments are helping me learn how to put it all together.

 

Thanks again!

Lisa

[TqB]

1 hour ago, LisaL said:

I've just discovered that my local university library has a partial collection of the Treatise, so I've had huge fun the past couple of days learning how to read it and browsing volume F. Your comments are helping me learn how to put it all together.

 

Thanks again!

Lisa

You're very welcome! The Treatise is a great resource, especially in the absence of a well stocked specialist library.

Volume F is good - do they also have  the much larger 2 volume supplement that supersedes it (Part F, Supplement 1, volumes 1&2, 1981)? It was put together by the legendary Dorothy Hill who was a fine researcher. It's still getting on a bit of course but I believe most of it stands.

[LisaL]

6 hours ago, TqB said:

You're very welcome! The Treatise is a great resource, especially in the absence of a well stocked specialist library.

Volume F is good - do they also have  the much larger 2 volume supplement that supersedes it (Part F, Supplement 1, volumes 1&2, 1981)? It was put together by the legendary Dorothy Hill who was a fine researcher. It's still getting on a bit of course but I believe most of it stands.

The two volume supplement is what I actually brought home! I only stumbled on it by accident, though, after I couldn't locate the other volume F. The amount of information these contain is overwhelming. I can't even imagine being in charge of sorting it all out. (I had never heard of Dorothy Hill before your mention, so off to Google I went, and now I'm intrigued! I've requested the 4 volumes of 'Carboniferous Rugose Corals of Scotland' from interlibrary loan. )

[TqB]

5 hours ago, LisaL said:

The two volume supplement is what I actually brought home! I only stumbled on it by accident, though, after I couldn't locate the other volume F. The amount of information these contain is overwhelming. I can't even imagine being in charge of sorting it all out. (I had never heard of Dorothy Hill before your mention, so off to Google I went, and now I'm intrigued! I've requested the 4 volumes of 'Carboniferous Rugose Corals of Scotland' from interlibrary loan. )

That's a brilliant monograph and still largely valid - works for the whole UK. If they have the first edition rather than the reprint, the plates are fabulously detailed and I can use a x25 stereo microscope on them. The reprint is just normal dots when you magnify it a bit and the images are mostly a bit small as they're actual size.

[LisaL]

4 hours ago, TqB said:

That's a brilliant monograph and still largely valid - works for the whole UK. If they have the first edition rather than the reprint, the plates are fabulously detailed and I can use a x25 stereo microscope on them. The reprint is just normal dots when you magnify it a bit and the images are mostly a bit small as they're actual size.

Ooooh, I can't wait to see! I really need to invest in a stereo microscope. Right now, I'm using a point-and-shoot camera that has a "microscope mode" feature on it. It captures a good bit of detail, but I have to take a zillion pictures to see all the angles! Maybe I can get someone at the university to let me come in and use one of theirs.  

 

I double-checked the editions I requested, and I'm pretty sure they're the first editions (pub. 1937-41). I'll report back when they arrive! 

[LisaL]

Hi, everyone. I have some new information on this little specimen and wanted to update this post from last summer!

 

I sent a piece of this little chain coral across the pond to @TqB a couple of weeks ago, and he examined it more closely and uncovered some details I had not noticed:

 

The coral is encrusting a stromatoporoid! Photos 1 and 2 show clear laminae and pillar structure at the base: 




Viewed in longitudinal section, it's clear that my specimen has globose diaphragms inside the coenenchymal tubules. These globose diaphragms are diagnostic of the genus Cystihalysites. (In Halysites, the diaphragms are flat.)

Photos 3, 4, and 5: Coenenchymal tubules with concave upward diaphragms clearly visible in several:







Photo 6, The illustration of Cystihalysites from the Treatise on Invertebrate Paleontology, p F436, showing the concave, upwardly-curved diaphragms and peripheral budding:



Photo 7, My specimen (right) with an illustration of Halysites encrustans from Buehler's 1955 Yale-Peabody publication (left). It's now called Cystihalysites encrustans (Buehler):



It's looking as though my specimen is likely Cystihalyistes encrustans, or something very similar, rather than Hexismia! One mystery, though, is that the type locality is a long way from Michigan, on the east coast of Quebec, which wouldn't be on a glacial route here. Tarquin suggested the possibility of a slightly different species. He also pointed out that the Treatise lists the genus from B.C, the whole of Canada, Utah, and Tenn in North America. We figured it stands to reason that the genus would occur somewhere between B.C. and Quebec for a possible source!

 

Thanks, Tarquin, for the beautiful photos and for helping me sort out the fascinating details! And thank you to everyone who contributed on the thread last year, @FossilDAWG, @Tidgy's Dad, @hemipristis. It's greatly appreciated!

 

[Tidgy's Dad]

Very interesting indeed.

Thank you for the update and thanks to Tarquin, too. 

[TqB]

Huge thanks @LisaL for the specimen (and others) (a complete surprise gift  ), and for the update here!

 

By the way, in case anyone asks - the stromatoporoid is definitely at the base of the coral. The corallum expands away from the base, and way up criteria in the corallites clinch it.

Edited September 11, 2020 by TqB