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Ordovician Coral Maybe?


Bev

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Ordovician


I want to say Galena because that is easy, but it may be Maquoeta (sp?) Shale.


SE Minnesota



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End pics in reply. :)



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Coral yes, but it looks quite weathered. Is there a chance it could have been brought in from another area by rivers or glaciers?

Context is critical.

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Hmmm, I found it on a high road cut with lots of Ordovician brachs, bryozoans, trilo molts, etc. This area was not glaciated during the last pass but the deeply cut river valleys, etc. were created by melting glaciers flowing toward the great Warren River system, now the Mississippi Valley. That said, it is perfectly possible that it got brought down from the north and as the glaciers melted it was deposited in a top layer and has just weathered out onto an Ordovician road cut.

I find the structure to be rather fascinating. It vaguely, to me, resembles Halysites coral that is very worn. Too me, it does not look like a horn coral. Realize I know nothingI :) Simply haven't seen anything like it before and that is why I posted it.

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No one is going to take a stab at this? It is an intriguing little piece.

So, what do you do with fossils that you can't get identified?

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Put it on the same shelve as all the other you can't get identified

It does look like every worn coral ???

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Thanks Grampa Dino. In other words I should start a "What's This" bucket. :P

I was looking at the Fossils of Ohio book I just got in and it also looks like some of the bryozoans in there. My first reaction when I found it was a piece of deer antler! :)

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Definitely a worn rugose solitary coral - the septa and dissepiments are very clear.

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Definitely a worn rugose solitary coral - the septa and dissepiments are very clear.

THANK YOU!!! :D

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Here is a USGS pdf. on the Paleozoic Corals of Alaska that has good pictures and an enormous amount of information. Our local geology is the same age and has broad similarities lithologically, but were probably deposited in different bodies of water.. Your find looks like it could be either Cyathophylloides or Rhaphidophyllum sp. found on pages 56 and 57.

I have a morphologically similar fossil found near Stillwater, MN that is late Cambrian. I can't tell if it is coral, sponge, or algae. It lacks the vertical striations, but the end view is very similar. I shall attempt a photo, and post it for comparison if the light cooperates.

In any case, the names of the corals suggest to me that they grow like different calcifying algae? Or is it that this paper was published in 1975 and the corals have been reclassified as algae?

Sorry to add only questions to your post Bev. I wish there was more up to date information particular to our area on the internet. Old books are helpful, but so confusing when the same organism has multiple names and classifications.

Edited to add photos of my tubular segmented fossil from Jordan Sandstone. I can't quite capture the fine textured surface patterns. It is chert/calcite/silica (?) inside a sandy layer with geometric patterns arranged in narrow bands.

Dry, side viewpost-14469-0-13724400-1399754935_thumb.jpg end viewpost-14469-0-12471900-1399753170_thumb.jpg

Wet, end view and other side. 2nd pic for scale and perspective.

post-14469-0-54557400-1399753222_thumb.jpgpost-14469-0-30328500-1399753237_thumb.jpg

There are segmented nodules that protrude, rootlike. This pic is blurred, but it shows how they stand out from the main branch.

post-14469-0-91763200-1399753304_thumb.jpg

Edited by Tethys
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Hey Tethys, they are similar!

I just can't get that pdf to open or download for me - darn shame, it sounded good.

Do you hunt in Minnesota often?

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...

So, what do you do with fossils that you can't get identified?

Good question...

Just because you can't ID it doesn't mean it's useless - Do what I do: just leave the 'name' field blank (fill in the location/etc as usual) and keep it with all your other fossils!

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Hey Tethys, they are similar!

I just can't get that pdf to open or download for me - darn shame, it sounded good.

Do you hunt in Minnesota often?

I do not get out hunting as much as I would like.

If you put the title of my link and USGS into google, it should find the report for you. It is a huge PDF file! I have good download speeds and it took nearly ten minutes for it to download enough so it wasn't just showing me a blank white screen.

These fossil ID sheets have good drawings of many different corals, though I'm pretty sure they are Devonian species I think mine is closest to a branching Thaumnopora or a pipe-organ Acinophyllum, and yours to a Heliophyllum horn coral. I am certain of the provenance of mine, though it is possible that it is karst debris from the overlying early Ordovician, Prairie Du Chien formation.

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Thanks Tethys! That Ohio fossil ID sheet of 5 pages was great! I downloaded all 5 pages, must be done separately.

If you are down in Minnesota sometime feel free to contact me and I can take you hunting here. :-D

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Put it on the same shelve as all the other you can't get identified

It does look like every worn coral ???

Good question...

Just because you can't ID it doesn't mean it's useless - Do what I do: just leave the 'name' field blank (fill in the location/etc as usual) and keep it with all your other fossils!

Never ceases to surprise me how some people do actually dispose of or dismiss everything they can not identify. In my collection those are often the most exciting specimens.

There are only a handful of mid-continent rugose corals known from the Upper Ordovician. Keep scouring the literature and you will find the answer.

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There are only a handful of mid-continent rugose corals known from the Upper Ordovician. Keep scouring the literature and you will find the answer.

I have scoured what is available online for Cambrian and early Ordovician coral in MN An image search returns my own photos. :(

If you can find stuff that is pertinent to our area, it invariably uses outdated terminology for the formations. I can find stuff on my St Croixan series faunas, but it requires a lot of detective work to figure out the correct ages and name of the fossils. ie- cryptozooan = stromatolites Tryblidiida *= monoplacophora

*link to excellent article which should be bookmarked for all Minnesota fossil hunters.

Wooster geologists has the best images, and the following reference list that sounds promising.

Elias, R.J. 1983. Middle and Upper Ordovician solitary rugose corals of the Cincinnati Arch region. United States Geological Survey Professional Paper 1066-N: 1-13.

Elias, R.J. 1989. Extinctions and origins of solitary rugose corals, latest Ordovician to earliest Silurian in North America. Fossil Cnidaria 5: 319-326.

Nicholson, H.A. 1875. Description of the corals of the Silurian and Devonian systems.Ohio Geological Survey Report, v. 2, part 2, p. 181-242.

Patzkowsky, M.E. and Holland, S.M. 2007. Diversity partitioning of a Late Ordovician marine biotic invasion: controls on diversity in regional ecosystems. Paleobiology 33: 295-309.

I am particularly interested in the marine invasion paper. The invaders are well documented, but the native Cambrian and Early Ordovician species are not.

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Bev,

While your specimen is definitely a solitary rugosan coral, I doubt you'll be able to get a confident ID on it. It's very worn and some critical pieces, such as the very early growth stages (located at the very tip of a complete horn coral) and the calyx (at the top, where the living coral animal was located) are missing. At a minimum, a confident ID would require you to prepare both transverse and longitudinal thin sections at several stages of the development of the coral.

Some genera can be excluded at this point, Grewingkia has long septa that meet at the middle of the coral and anastomatize to form a spongy columella that occupies at least half the total diameter of the coral. You would be able to see this in your specimen, and it is not there. Other genera, such as Lobocorallium and Dieracorallium have septa that are enlarged so they form a solid mass that fills the entire volume of the coral, except for the earliest growth stages. They are also markedly trilobate (3 lobes in cross section). Your specimen doesn't fit that description. Bighornia has septa that also fill the coral, but it is highly flattened on one side and has a small but prominent lens-shaped columella in the middle. Again this seems different from your specimen.

On the other hand there are several species of Streptelasma and Helicilasma that occur in the Upper Ordovician. Helicilasma differs from Streptelasma in that, in the earliest growth stages the septa are dilated and fill the body of the coral (almost no space between septa), compared to Streptelasma where the septa are thin (not dilated) at all growth stages. In both genera the septa do not reach the middle, or reach but form a very loosely organized columella. Your coral could be either genus, and there are several species in each genus.

We should also consider the possibility that your specimen is a small piece of a phaceloid colonial rugose coral such as Paleophyllum or some species of Favestina. Phaceloid coral colonies are made up of individual corallites that are not in contact, so each corallite is a separate tube. Your specimen could be a piece of one corallite from such a colony.

All of the genera I mentioned occur in the Upper Ordovician, either in the Galena or Maquoketa, or in correlative formations such as the Stoney Mountain Formation in Manitoba and Wyoming.

Don

Edited by FossilDAWG
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Tethys,

Solitary rugosans with mineralized skeletons appeared in the Middle Ordovician, starting with very simple cones with short septa but no tabulae or dissepiments. In North America the earliest rugosan coral is Lambeophyllum, which is common in some early Middle Ordovician limestones. Similar forms appeared almost simultaneously in what is now Russia and Australia. A very few Late Cambrian coral-like fossils have been reported, but these are very small and were found by etching limestone in acid and picking out microscopic silicified fossils. This is why you are not finding references to Cambrian and Early Ordovician corals in your area (or any area).

The specimen in your photo has no features that would identify it as a coral. Specifically, it lacks a corallite wall (a shell layer around the outside), septa (partitions that start at the outer wall and extend at least some distance into the interior), or tabulae (horizontal partitions). To be frank I don't see anything in the photos that convinces me the specimen is a fossil, as it seems to lack any distinctive internal structure and it has no symmetry (not bilateral, not radial). It could be something like a sponge I suppose.

Don

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I believe it is a cylindrical stromatoporoid . This is Aulacera (Breatricea) undulata. U.Ordovician of KY. Forgot scale largest is 1.5" wide x 2" long.post-2520-0-35315500-1400020880_thumb.jpgpost-2520-0-18755000-1400020892_thumb.jpg

Edited by Herb

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Thank you Don and Herb. :)

That explains why my fossil list completely omits coral.

It lists several sponges, and stromatoporoids in general, but no mention of a cylindrical growth form.

It could be either of those, or a calcifying algae. I don't know enough of the fine details of morphology to identify it beyond that point. Algal-strome reef complex and associated fauna is well documented from several Cambrian strata and the Early Ordovician limestone in the St. Croix river valley.

I wish I could capture the fine surface patterns of my specimen, and the spiral growth form.

It looks like a cup in a segmented armored plate thallus from both ends, it spirals, has odd wart like protuberances and very fine surface patterns of raised donuts in well defined transverse bands. The warts are segmented and have a pin-prick sized X shaped slit with a circle at the ends of the x in each segment.

I tried a search with those details and came up with Lithothamnion as a good match for an algae. Trying to search the literature on Cambrian fossil algae just keeps slamming me into paywalls, and its far too nice outside to hang out on-line. The garden will not plant itself. :)

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