Adam's Ordovician.

[Jackson g]

Been too long since I've peeked this thread, guess I should follow it. Great stuff Adam!

[Tidgy's Dad]

On 4/15/2021 at 10:58 PM, Jackson g said:

Been too long since I've peeked this thread, guess I should follow it. Great stuff Adam!

Thank you, Jackson, glad you're back on board. 

 

The Rafinesquina alternata specimen posted at the bottom of the previous page is also interesting as it also has several species of bryozoan either attached to the shells or in the matrix stuck underneath the sample. 

Here is an encrusting Atactoporella schucherti, a species commonly found on Rafinesquina in the Waynesville and Lower Whitewater Formations.

 

Notice the rather dimpled surface which is a characteristic of the genus.

[Tidgy's Dad]

I've found a few similar to this next one attached to Rafinesquina valves. I think they're bryozoan 'holdfasts'. No guess as to the genus as whatever grew out of it may have been ramose / bifoliate or ramose; branching or 'stick'. It has rather lovely zooecia and mesozooecia, though.

[ClearLake]

22 minutes ago, Tidgy's Dad said:

I think they're bryozoan 'holdfasts'.

Adam, I believe you are correct. I always find these interesting for some reason, maybe just because I don’t see them nearly as often as I think I should in these rocks. Bryozoan debris makes up a significant percentage of some of these rocks and it seems the holdfast would be one of the more durable parts, so it seems there ought to be more of them. Ah, the vagaries of fossil preservation (or my powers of observation)!  Anyway, thanks for showing us the fine details of your specimens.

[Tidgy's Dad]

On 4/21/2021 at 1:54 PM, ClearLake said:

Adam, I believe you are correct. I always find these interesting for some reason, maybe just because I don’t see them nearly as often as I think I should in these rocks. Bryozoan debris makes up a significant percentage of some of these rocks.

Some of them just had a pointy end that stuck into the soft substrate, but yes, I'd expect to see more. Bryozoans proliferated in these Cincinnatian rocks, there were so many species, especially in the Waynesville and Whitewater Formations it would seem. 

Here's the reverse of that Rafiesquina, the matrix contains a couple of larger bryozoan chunks a a small 'stick' bit and several micro-fragments of different species. 

The big, flattened, branching one at the top would appear to be a species of Homotrypa of which there are at least ten species in these formations. I would guess at this one being H. flabellaris, all things being considered, but I wouldn't bet a brachiopod on it.

Edited April 22, 2021 by Tidgy's Dad

[Tidgy's Dad]

At first, I thought the one below was a Streptelasma divaricans rugose coral judging by its size and shape though I don't have any specimens to compare. 

Then I decided it was a Streptelasma coral totally encrusted by a bryozoan. But I can't locate any signs of septa. Hmmmm.

So now I believe it's a really weird bit of a bryozoan colony, perhaps another species of Homotrypa. 

Maybe.

 

[Tidgy's Dad]

I think the little stick bryozoan, which has a stem 2 mm wide, is Bythopora delicatula. It has oval zooecial openings that meet the surface at an angle. 

 

[Tidgy's Dad]

This tiny fragment in the top right quarter of the photograph, could be Stictopora lata. Bifoliate, dividing and with oval to sub-rectangular zooecia arranged in rows. 

[Tidgy's Dad]

Several tiny 1 to 3 mm fragments in these photos. 

Top centre maybe another bit of Stictopora lata? 

Centre left, the long thin Stictopora emacerata.

And right centre a broken piece of Fenestella granulosa.   

Fenestella granulosa is nice as it is from a time when the fenestellids were still a comparatively minor group which became increasingly successful through the Silurian and Devonian before becoming a dominant part of the bryozoan fauna in the Carboniferous and Permian. Good to have an early one.

[Tidgy's Dad]

Also from Miamisburg, Ohio, here are a couple of Hebertella occidentalis :

Most of the growth lines are very fine, but one or two are very obvious suggesting a sudden change in conditions. 

[Tidgy's Dad]

When Debra first posted me a photo of the rock in the top right of this box, before she sent it to me, I thought, 'Ah, more Vinlandostrophia ponderosa, nice." 

From somewhere around Dayton, Ohio. 

But when I received the rock I also spotted lots of tiny Zygospira modesta. And I do mean tiny. It is interesting that there are no bryozoans in this piece, most unusual in the Cincinnatian, not much else at all except the two species, only a couple of fragments of shattered thin shelled brachiopod, probably Rafinesquina sp. And one delightful surprise. 

What was also noticeable was that both the V. ponderosa and the Zygospira were much smaller than specimens I have from several other locations. 

So what was going on? A high energy environment where only sturdy, rounded species with a strong pedicle could flourish and even bryozoans couldn't establish themselves? And a lack of food ? 

Here is the best of the Vinlandostrophia ponderosa specimens. 

[Kane]

That would be very interesting if the size and shape were strongly correlated to nutritional availability and turbulence of environment. I would definitely buy your explanation as being the most probable in terms of the successful V. ponderosa here!

[Tidgy's Dad]

18 hours ago, Kane said:

That would be very interesting if the size and shape were strongly correlated to nutritional availability and turbulence of environment. I would definitely buy your explanation as being the most probable in terms of the successful V. ponderosa here!

Modern brachiopod growth can be related to nutrition, but also to temperature, depth and the space to grow. I can't remember if someone has studied the effects of turbulence, though that might be related to depth on occasion. 

 

Most Vinlandostrophia ponderosa belong to the variety / subspecies V. ponderosa ponderosa. 

Looking closer, I found this specimen that has fewer costae on the slopes (five rather than 6 to 8), a more rounded outline compared to the usual quadrate form and no 'ears' that V. ponderosa ponderosa exhibits. These characteristics are diagnostic of the more unusual form Vinlandostrophia ponderosa auburnensis found only in the Mount Auburn member of the MacMillan Formation. ( or the Mount Auburn Formation in Kentucky). 

Jin and Zhan (2000) transferred this subspecies to the genus Gnamptorhynchos, but this seems not to be accepted by most others. 

Where the specimen is broken, one can see calcite crystals inside. This often happens with big brachiopods in the Cincinnatian, geodized specimens are common.

Here is a fragment of another Vinlandostrophia geode, found in the same piece of rock :

Narrowing this down to the Mount Auburn is also interesting in that the faunal list from this Formation / Member is not as long as those from many other Formations in the Cincinnatian; the Fairview, Waynesville, Liberty etc. 

Were conditions not as favourable at this time? And became even worse for the period when these particular sediments that make up my rock were laid down? 

Edited May 2, 2021 by Tidgy's Dad

[Tidgy's Dad]

There were a large number of Zygospira modesta present in the rock. Most of them were complete, or nearly so, though I broke a few bashing them free. I haven't prepped them as it would take forever. Several of these bits contain up to four specimens and there are others still attached to matrix on some of the other fossils from the chunk.

Here are the biggest ones : 

And compared to an average specimen from the St. Leon road-cut : 

And the smallest ones, smaller than any others I have, I think :

A couple of pretty, medium-sized ones; the one on the left shwing the sulcus and the one on the right the fold : 

[Tidgy's Dad]

There were also several fragments of a thin shelled brachiopod, I'm guessing Rafinesquina alternata, as it looks like it and it's just about the only other articulate brachiopod that occurs in the Mount Auburn. 

The pieces are from 1 to 1.5 cm at their widest.

 

[Tidgy's Dad]

But the surprise prize of this rock was this little beauty. 

Tis the inside of the pedicle valve of the discinid Trematis millepunctata. 

Another new species for my Cincinnatian collection.  

The counterpart. This split so well. 

Notice the slit in the valve between the apex and the posterior edge.  This is the pedicle opening, Trematis seemed to have had a very large and strong pedicle and a was a shallow water species which adds to my hypothesis that the species in this rock possibly lived in a turbulent environment. 

Thickened rim on the central end of the slit and muscle scars adjacent to them : 

The valve exterior is heavily pitted, here, where some of the inner layers have broken away, these pits are clearly visible :

 

[Tidgy's Dad]

From West Chester, near Dayton, Ohio comes this lovely Vinlandostrophia annieana, 2.7 cm acrosss at its widest across the hingeline. Ten plications on the lateral slopes each side of the fold on the brachial valve. Plenty of bryozoan/ crinoid holdfast epibionts, as is often the case. 

 

11 plications on the flanks each side of the sulcus on the pedicle valve. Three major plications in the sulcus but also some secondary ones :

The interareas of both valves are steeply inclined.

Moderately deep sulcus showing multiple plications : 

Pretty growth lines :

The epibionts :

[Tidgy's Dad]

And this one, also from the Richmondian of West Chester, near Dayton, Ohio is a larger Vinlandostrophia annieana, I think.  It looks a lot like V. moritura, but doesn't seem to have enough plications on the flanks. 

Four costae on the fold, the central two a little stronger than the outer pair. Broad lateral plications on flanks

This one has three equal plications in the sinus, which is also possible for V. anniena, as well as five as in the previous specimen.

Sloping interareas : 

A bit of abnormal growth :

Bryozoan goop : 

Another great big thank you to Debra @Paleome for the wonderful Ohio specimens posted above. 

Edited May 8, 2021 by Tidgy's Dad

[Tidgy's Dad]

I won these in an auction lot from the marvelous @Misha

These are his photos of the specimens. 

 

The Vinlandostrophia on the left is 2.6 cm wide and the one on the right a little over 3 cm wide.

They were said to be from the Lower Silurian Brassfield Formation of Kentucky.  Do you have any further location details, please, Misha? 

However, although there are a couple of species of Vinlandostrophia known from the Brassfield Fm, these specimens are not they.

Paleontology of Kentucky, by W.R. Jillson, 1931: Chapter Three, Silurian Fauna (uky.edu)

These are rather too large and I'm pretty sure they're V. ponderosa ponderosa from the Late Ordovician. 

See also this thread which has a similar conclusion.   A few recent finds(Brassfield Formation) - Fossil ID - The Fossil Forum

It's not a worry though, Misha, as I was aware of this whilst bidding for the lot and am quite happy with the specimens. 

Also a nice bit of crinoid stem? 

And this. Conodont? Bit of broken brachiopod? 

Thanks, Misha. 

Edited July 9, 2021 by Tidgy's Dad

[Misha]

 

 

2 hours ago, Tidgy's Dad said:

These are rather too large and I'm pretty sure they're V. ponderosa ponderosa from the Late Ordovician. 

See also this thread which has a similar conclusion.  

I believe you might be correct on this, the same seller that I bought these fossils from has recently listed a batch of Hebertella sp. listed as Devonian fossils, this really made me doubt all of what they have told me and since this is KY I think it is much more likely to be a Late Ordovician deposit.

And I think that makes much more sense considering all of the fossils and the region, even though they are found in the Silurian a bit they are far more prevalent in the Ordovician and so are the Ordovician deposits in that area.

I'm glad you liked them though! And that crinoid bit is quite cool, I didn't notice it or even know they could be found in these formations.

Edited July 9, 2021 by Misha

[Tidgy's Dad]

1 hour ago, Misha said:

 

 

I believe you might be correct on this, the same seller that I bought these fossils from has recently listed a batch of Hebertella sp. listed as Devonian fossils, this really made me doubt all of what they have told me and since this is KY I think it is much more likely to be a Late Ordovician deposit.

And I think that makes much more sense considering all of the fossils and the region, even though they are found in the Silurian a bit they are far more prevalent in the Ordovician and so are the Ordovician deposits in that area.

I'm glad you liked them though! And that crinoid bit is quite cool, I didn't notice it or even know they could be found in these formations.

Do we know where in Kentucky? 

[Misha]

1 hour ago, Tidgy's Dad said:

Do we know where in Kentucky? 

I believe it says that they have a blog where they discuss this stuff, I'll see if I can dig anything up. If not it may be possible to contact them directly.

 

I'll tell you if I get any more info via PM

[FossilNerd]

On 7/9/2021 at 12:33 PM, Tidgy's Dad said:

Do we know where in Kentucky? 

I might be able to help narrow it down to a formation, if we know a general area.  

[Tidgy's Dad]

12 hours ago, FossilNerd said:

I might be able to help narrow it down to a formation, if we know a general area.  

Hi, Wayne. Glad to see you back in the Ordovician. 

Road cuts from Fleming and Bath counties is the information I've now received. 

[Tidgy's Dad]

Those of you who follow this thread or know me, will be aware of how much I love hash plates. 

I don't get too many from North America due to the size, weight and resulting postal charges, so I was delighted when I recently received this one from my friend Debra @Paleome. It's from the Dayton, Ohio area. 

 

The above photos are as it arrived. It's centred around a lovely group of rhynchonellids though there are bits of other brachiopod species, crinoid stems and poorly preserved "stick' bryozoans that make up the majority of the matrix. I haven't fully prepped the piece as I have good examples of these species already, it would take too long, prepping these rhynchs is a nightmare due to the finely spaced and deep growth lines and I broke a crinoid stem while being a little over-zealous. Still took quite a few hours to get this far : 

The reverse; mainly strophomenates : 

These rhynchonellids are mostly Lepidocyclus perlamellosum, a little bigger, not as rounded and with more conspicuous growth lines to the Hiscobeccus capax here. There are four in the central clump. 

Details; bottom right is the sole specimen of the slightly smaller, more rounded and less marked by growth lines Hiscobeccus capax. 

And the Hiscobeccus capax :

Edited July 23, 2021 by Tidgy's Dad